SS 1 First Term

Learning Objectives

• Define a computer system and name its parts.
• Describe the input, process and output model.
• Distinguish between data and information.
• State the units used to measure data.

What is a Computer System?

A computer system is a complete, functional unit that combines physical hardware, software instructions, data, and the people who operate it. No single component works in isolation; the system only produces useful results when all four parts cooperate. Hardware provides the physical machinery, software provides the instructions that tell the hardware what to do, data is the raw material that enters the system, and users follow procedures to operate it.

The hardware component includes every physical part you can touch, such as the central processing unit (CPU), keyboard, monitor, mouse, printer, and storage drives. Software refers to the programs and instructions that direct the hardware; examples include operating systems like Windows, applications like Microsoft Word, and web browsers like Chrome. Data consists of raw facts and figures that have not yet been processed; for example, a list of student examination scores is data. Users are the people who interact with the system, and procedures are the rules they follow, such as logging in with a password.

Think of a computer system like a choir. The hardware is the voices and bodies, the software is the song and the conductor's instructions, the data is the words being sung, and the users are the choir members and conductor all following the same procedure. Without any one of these elements, the choir cannot perform.

This table summarises the four components, but the key idea is that they depend on each other. Hardware alone is useless without software to run it, and software alone is useless without hardware to execute it.

The Input-Process-Output (IPO) Model

Every computer task, from sending a text message to printing a report, follows the Input-Process-Output (IPO) model. This model describes how data moves through a computer system. First, data is entered through an input device such as a keyboard or mouse; this stage is called input. Second, the CPU processes the data by performing calculations, comparisons, or sorting; this stage is process. Third, the result is presented to the user through an output device such as a monitor or printer; this stage is output. Sometimes the data or results are also saved for later use, which is storage.

For example, when a cashier at a supermarket keys a customer's purchases into a computer, the items and prices are input. The computer calculates the total and updates stock records; this is the process. The total displayed on the screen and the printed receipt are the output. If the transaction is saved to a file, that is storage. The IPO model is central to understanding how every computer system works, and it will appear in every week of this course.

Storage is sometimes shown as part of the cycle because results and data are often saved; the core model remains input, process, output.

Role of the CPU

The Central Processing Unit (CPU) is the brain of the computer. It carries out every instruction of a program by following a repeated cycle called the machine cycle. The machine cycle has four steps, namely fetch, decode, execute, and store. In the fetch step, the control unit retrieves the instruction from memory. In the decode step, the control unit determines what the instruction means. In the execute step, the arithmetic and logic unit (ALU) performs the calculation or comparison. In the store step, the result is saved to a register or memory. A modern CPU performs billions of these cycles per second, measured in gigahertz (GHz).

Every calculation, comparison, and decision happens in the CPU. Without the CPU, the computer cannot process data. The CPU's speed and efficiency directly affect how quickly the computer completes tasks.

Data vs Information

Data and information are related but different concepts. Data refers to raw, unprocessed facts that may have little meaning on their own. For example, the numbers 70, 85, 60, and 90 are data. Information is data that has been processed into a meaningful, useful form. For example, when the average of those numbers is calculated as 76.25, that result is information. Data becomes information after processing, and information helps people make decisions.

This distinction is important because computers exist to turn data into information that humans can use.

Binary Representation

Computers cannot store words, pictures, or sounds directly. Instead, all information inside a computer is represented using only two values, 0 and 1. These two values are called bits (binary digits). Because the computer's hardware uses electronic switches that are either on or off, it is natural to use two symbols, 0 for off (no electrical charge) and 1 for on (electrical charge). This two-symbol system is called binary. Everything we see on a computer, text, numbers, images, sound, video, is ultimately stored as patterns of 0s and 1s.

Each character, whether a letter, digit, or symbol, is given a code. For example, in the ASCII system, the letter A is represented as 01000001, which is one byte (eight bits). The word CAT needs three bytes because it has three characters. Binary is the foundation of digital technology.

Units of Data

Data is measured in units that get progressively larger. A bit is the smallest unit, a single 0 or 1. Eight bits make one byte, enough to store one character. A kilobyte (KB) is 1024 bytes, roughly a short page of text. A megabyte (MB) is 1024 KB, enough for a song or a small photo. A gigabyte (GB) is 1024 MB, enough for a movie. A terabyte (TB) is 1024 GB, enough for a large hard drive. Understanding these units helps you estimate how much storage you need for different files.

Digital Technologies and Their Impact

Digital technologies use binary (0s and 1s) to store, process, and transmit information. They include the devices we use every day, such as computers and smartphones, the software that runs on them, such as apps and operating systems, and the networks and services that connect them, such as the internet and cloud computing. Digital technologies have transformed how we live because they make tasks faster, cheaper, more accurate, and often accessible from anywhere.

In Nigeria, digital technologies are used in education through online lessons and virtual classrooms, in banking through mobile money and POS terminals, in health through electronic health records and telemedicine, in agriculture through weather apps and market price apps, in transport through GPS and ride-hailing apps, in communication through email and social media, and in government through e-government services.

Benefits of digital technologies include speed (tasks done in seconds), accuracy (fewer manual errors), storage (huge amounts of data on small devices and in the cloud), connectivity (instantly reaching people everywhere), accessibility (services available from anywhere at any time), and automation (machines performing repetitive work).

Challenges include security and privacy risks such as hacking and data theft, the digital divide where some people or areas lack access, over-reliance and screen-time concerns, the cost of devices and data, and misinformation spreading rapidly online. Understanding both benefits and challenges helps you use digital technologies wisely.

Practical Work

1. Draw and label the parts of a computer system.
2. Give two examples of data being turned into information.
3. List the units of data from the bit to the terabyte in order.
4. Name four digital technologies you use and state one effect of each.

Scenario-Based Questions

1. A school clerk keeps paper registers and then enters the same marks into a spreadsheet. Using the four components of a computer system, explain why the hardware, software, data, and user must all be present for the exercise to succeed, and what happens if any one is missing.
2. A cyber cafe owner tells a customer that data and information mean the same thing. Using the example of the raw scores 70, 85, 60, and 90 and their calculated average, correct the owner and justify why the distinction matters for decision making.
3. A market trader records each sale in an exercise book while a competitor uses a POS machine and an app. Compare the two approaches using the benefits and challenges of digital technology, and predict which trader will find it easier to know the month end profit, giving reasons.
4. A village school receives solar powered tablets for lessons, and the head teacher asks what the school should prepare for. Using the benefits and challenges in your note, predict two good outcomes and two difficulties the school should plan for.
5. A school typist wants to produce the final term report from a list of raw scores. Using the Input Process Output model, trace step by step what happens from typing the scores to printing the report, and state where storage fits in.
6. A student claims that one kilobyte can hold exactly one thousand characters. Correct the student using the units in your note, explain how many bytes a kilobyte really is, and show how to estimate how many short pages of text fit inside a gigabyte.
7. A friend says a computer is just a machine for typing letters. Using binary representation and the workload of the CPU, explain why every letter, image, and sound inside the machine is digital, and why the CPU's machine cycle matters even for a simple document.

Learning Objectives

• Name the early calculating devices in order.
• State the contributions of Charles Babbage and Ada Lovelace.
• Describe the first electronic computers.
• Explain how transistors and integrated circuits changed computing.

Early Calculating Devices

People invented tools for calculation long before electricity. The need to calculate is as old as trade itself. The abacus, dating back to around 2400 BC, is one of the oldest known calculating tools. It consists of a wooden frame with rods and beads. The user moves beads to represent numbers and performs addition, subtraction, multiplication, and division. Abacuses were used in ancient Mesopotamia, China, Egypt, and Rome. Even today, some shopkeepers in parts of Asia still use an abacus because it is fast and reliable when the operator is skilled.

In 1617, John Napier invented a set of numbered rods called Napier's Bones that made multiplication easier by breaking it into simpler additions. Later, the slide rule, invented around 1622 by William Oughtred, used sliding scales to perform multiplication, division, and even roots. Slide rules were used by engineers well into the 1970s.

Blaise Pascal, a French mathematician, built the Pascaline at age 19 to help his father with tax calculations. It used a series of interlocking gears to add and subtract numbers. Gottfried Leibniz improved on Pascal's design with the Leibniz Wheel, a machine that could also multiply and divide. Leibniz also developed the binary number system that computers use today.

Charles Babbage and Ada Lovelace

Charles Babbage designed the Difference Engine in 1822 to calculate mathematical tables automatically. He later designed the Analytical Engine in 1837, which had a mill (like a CPU), a store (like memory), and could follow instructions on punched cards. It was never fully built in his lifetime, but it contained the core ideas of every modern computer, namely processing, memory, and programmability.

Ada Lovelace, working with Babbage, wrote detailed step-by-step instructions for the Analytical Engine to compute Bernoulli numbers. These instructions are widely regarded as the first computer program, and Ada is celebrated as the first computer programmer. Her insight was that the machine could manipulate symbols, not just numbers, making it a general-purpose computer.

The First Electronic Computers

ENIAC (Electronic Numerical Integrator and Computer) was built at the University of Pennsylvania by John Presper Eckert and John Mauchly. It was completed in 1945 and could perform 5,000 additions per second. ENIAC contained about 17,468 vacuum tubes, weighed 27 tons, and filled a large room. It was general-purpose, meaning it could be reprogrammed to solve different problems, though reprogramming took days of rewiring cables.

UNIVAC I (Universal Automatic Computer) was the first computer manufactured and sold commercially in the United States. It was designed by the same team and was used by the US Census Bureau. UNIVAC famously predicted the result of the 1952 presidential election on live television. UNIVAC introduced magnetic tape for data storage, replacing punched cards for many tasks and making data handling faster.

Vacuum tubes were glass bulbs that controlled electrical flow. They were large, fragile, consumed enormous amounts of power, and generated intense heat. ENIAC needed a dedicated air-conditioning system. These limitations motivated inventors to find a smaller, cooler, cheaper alternative.

Transistors, Integrated Circuits, and Modern Computing

The transistor was invented at Bell Laboratories in 1947 by John Bardeen, Walter Brattain, and William Shockley. A transistor performs the same switching function as a vacuum tube but is far smaller, uses less power, generates less heat, and lasts much longer. Computers built with transistors (second generation, roughly 1956 to 1963) were smaller, faster, and more reliable. Programming languages like FORTRAN and COBOL were developed during this era.

Jack Kilby (Texas Instruments) and Robert Noyce (Fairchild Semiconductor) independently developed the integrated circuit in 1958. An IC places many transistors, resistors, and capacitors on a single small chip of silicon. This eliminated the need to wire individual components together. Third-generation computers (1964 to 1971) used integrated circuits and introduced operating systems, allowing multiple programs to run at once. Computers became affordable enough for schools and small businesses.

In 1971, Intel released the 4004, the first microprocessor, placing an entire CPU on one chip. This made personal computers possible. The fourth generation (1971 to present) saw the rise of personal computers, mobile devices, and the internet. The fifth generation (present and future) involves artificial intelligence, cloud computing, and networked systems.

Modern computing extends far beyond the desktop. Smartphones, tablets, wearables, servers in data centres, and cloud platforms all rely on the same principles developed over centuries. In Nigeria, digital computing powers mobile banking (e.g., OPay, PalmPay), e-learning platforms, government portals, health record systems, and the entertainment industry.

Practical Work

1. Draw a timeline from the abacus to a modern computer.
2. Match each early device with its inventor and its use.
3. Write two differences between a mechanical and an electronic computer.
4. Name the component that replaced the vacuum tube.

Scenario-Based Questions

1. A shopkeeper in a market town needs to add and subtract large daily totals without electricity. Between the abacus and the Pascaline, recommend the tool better suited to the job and justify your choice using what you know about how each one works.
2. A museum wants to display the machine that first contained the core ideas of every modern computer. Explain why Babbage's Analytical Engine deserves the display, and name the parts that foreshadow today's processing and memory.
3. A student reads that Ada Lovelace wrote a program for a machine that was never built. Explain why she is regarded as the first programmer, and what her insight about symbols made the Analytical Engine a general purpose machine.
4. ENIAC filled a large room, weighed 27 tons, and used about 17,468 vacuum tubes, yet a modern laptop is far more powerful. Trace the changes from vacuum tubes to transistors to integrated circuits to microprocessors that made this small and fast machine possible.
5. In the 1950s a company must choose between keeping a room of vacuum tube machines and switching to transistor machines for the same work. Compare size, power use, heat, and reliability, and recommend one with reasons from your note.
6. A supplier tells a school that the Intel 4004 is the reason cheap personal computers exist today. Explain what the 4004 was, when it was released, and why putting an entire CPU on one chip changed the market.
7. Imagine integrated circuits had never been invented. Using the generation table in your note, predict what the size, cost, and daily use of computers would be like in a modern office, and justify your prediction.

Learning Objectives

• State the main characteristics of a computer.
• Describe the motherboard and the system unit.
• Explain the roles of the CPU, the ALU, the control unit and the registers.
• Describe the buses, RAM and ROM.

Characteristics of a Computer

A computer has several distinctive properties that set it apart from other machines and make it a powerful tool. These characteristics work together to handle tasks that would be impossible or impractical for humans to do alone. Understanding them helps learners appreciate why computers are used in nearly every area of modern life.

Speed - Computers process data and execute instructions at extraordinary speed, handling millions or even billions of operations every second. Modern CPUs operate at clock speeds of 3 to 5 GHz, meaning they can perform billions of cycles per second. Example: A school computer can process the results of 1,000 students and produce a complete report in just a few seconds.

Accuracy - Computers perform calculations and process data with a very high level of precision. When errors occur, they are almost always caused by incorrect input data or flawed programs, not by the computer itself. Example: A calculator will always return the correct sum - if you type 15 + 27, the answer is always 42.

Diligence - A computer never gets tired, bored, or distracted. It can perform the same task for hours or even days without any drop in quality or speed. Example: A security camera system monitored by a computer can watch every angle of a building continuously for 24 hours without a break.

Storage Capacity - Modern computers can store enormous amounts of data in both temporary memory (RAM) and permanent secondary storage such as SSDs and hard drives. This data can be saved, retrieved, and searched almost instantly. Example: A single laptop can hold thousands of documents, photos, and videos, and you can find any one of them in seconds using a search function.

Versatility - A computer can switch between completely different tasks with equal ease. The same machine can be used for word processing, playing music, browsing the internet, and running scientific simulations. Example: You can use the same laptop to write an essay in Word, listen to music, check your email, and run a spreadsheet all within the same hour.

Automation - Computers can perform long sequences of repetitive tasks automatically once a program is set in motion, without requiring a human to give a command at every step. This saves time and reduces the chance of human error. Example: A payroll program calculates salaries, deductions, and bonuses for every worker automatically each month once the correct data is entered.

Reliability - Given accurate input data and correctly written instructions, a computer will consistently produce the correct result every single time. Errors in output are almost always caused by faulty data or bugs in the software, not by the machine itself. Example: Every time you type 7 + 8 into a calculator, it returns 15 - the result never changes or becomes incorrect under normal conditions.

No Feelings - A computer operates purely on logic and electrical signals, not on emotions. Its performance is never affected by mood, stress, or tiredness. Example: A grading program applies the same marking criteria to every paper whether it is the first or the thousandth, without any bias or fatigue.

No IQ - A computer has no independent intelligence. It cannot think, reason, or solve new problems on its own. It follows exactly and only the instructions given to it by a programmer. Example: A computer cannot solve a new type of mathematics problem until a programmer writes new code to handle it - otherwise it will simply display an error or produce wrong output.

Secrecy (Data Security) - Computers protect sensitive data through authentication, passwords, and encryption so that unauthorised persons cannot access or understand the information. These security measures are built into operating systems, applications, and network protocols. Example: Banking systems encrypt every transaction so that even if the data is intercepted during transmission, it cannot be read or understood by anyone without the correct decryption key.

Now that we understand these key characteristics, let us examine the physical components that make them possible - the motherboard and the system unit.

The Motherboard and the System Unit

The motherboard is the main circuit board inside the system unit. Every major component connects to it either directly or through cables. The motherboard holds the CPU socket, memory slots, expansion slots, chipsets, power connectors, and ports for input and output devices. Think of the motherboard as the central crossroads of a town with roads leading to every building, each building being a component such as the CPU, RAM, or a graphics card.

The system unit is the case that houses the motherboard and other components. Inside the system unit, you will find the motherboard, CPU, RAM, power supply, storage drives, and sometimes a graphics card and other expansion cards. Each component has a specific role and connects to the motherboard through standardized slots and connectors.

The motherboard is called the backbone of the computer because it provides the physical connections that allow all components to communicate. Without the motherboard, the CPU, RAM, and storage devices cannot work together.

The CPU, ALU, Control Unit, and Registers

The Central Processing Unit (CPU) is the brain of the computer. Inside the CPU are three main parts, namely the Arithmetic and Logic Unit (ALU), the Control Unit, and Registers. The ALU performs arithmetic operations (add, subtract, multiply, divide) and logic operations (compare values). The Control Unit fetches instructions from memory, decodes them, and directs the other parts to act. Registers are very fast, tiny storage locations that hold data and instructions during processing.

The CPU repeats the machine cycle for every instruction, namely fetch, decode, execute, and store. In the fetch step, the control unit brings the instruction from memory. In the decode step, it works out what the instruction means. In the execute step, the ALU or another unit carries it out. In the store step, the result is saved to a register or memory. A modern CPU performs billions of these cycles per second, measured in gigahertz (GHz).

For example, to calculate 5 + 7, the control unit fetches the instruction 'add 5 and 7', decodes it, the ALU adds the numbers to make 12, and the result is stored in a register. The same four steps run for every operation, whether the computer is playing a video or drawing a graph.

Buses, RAM, and ROM

A bus is a shared pathway that carries data, addresses, and control signals between components. The three main types are the data bus (carries the data itself), the address bus (carries the location or address in memory), and the control bus (carries commands such as read and write). A wider bus can move more data at once; a 64-bit data bus carries 64 bits in a single trip.

RAM (Random Access Memory) is the main memory that holds data temporarily while the computer runs. It is volatile, meaning its contents are lost when power is off. ROM (Read Only Memory) is permanent memory that stores startup instructions. It is non-volatile, meaning its contents remain even without power. A common comparison is a work desk (RAM) where you spread out papers while working, versus a filing cabinet (ROM/other storage) where things are kept permanently.

When a program runs, data enters through input devices, travels along buses to the CPU, is processed, held temporarily in RAM, saved permanently to storage, and presented through output devices. Every action on a computer involves several of these stages cooperating in a single coordinated flow.

System Unit Characteristics and the Motherboard

The system unit is the box that houses the main working parts of the computer. Its key characteristics are its form factor (desktop tower or slim laptop profile), its power supply, its cooling system and the space it provides for expansion. The system unit is where processing actually happens. All other devices, keyboards, monitors and printers, connect to it so that data can enter, be processed and leave as output.

At the centre of the system unit is the motherboard, the main circuit board. Every major component, the CPU, RAM, storage controllers, expansion cards and ports, connects to the motherboard through sockets and slots. The motherboard provides the electrical pathways that allow all the parts to exchange data, and it is the physical backbone on which the whole system is built.

Because the motherboard is the common link for every component, its layout helps decide how much memory can be added, which processors it supports and how quickly the components can communicate. Older computers used many separate chips; modern motherboards integrate sound, network and graphics functions directly onto the board, which reduces cost and saves space.

Form factors range from desktop towers to slim laptop designs.

The motherboard carries the CPU socket, RAM slots and expansion slots.

Tracks on the motherboard carry data between components.

Integrated sound and networking reduce cost and space.

CPU and Control Unit Responsibilities

The Central Processing Unit (CPU) is responsible for executing the instructions of every program. The control unit is the director of this process. It fetches each instruction from memory, decodes what the instruction means and controls which units carry it out, making sure data moves between memory, the ALU and the registers in the correct order.

The responsibilities of the control unit include reading instructions in sequence, interpreting the operation code of each instruction, generating the control signals that tell the ALU when to add, subtract or compare, and synchronising the machine cycle with the system clock. It does not calculate values itself; it directs the parts that do.

The CPU as a whole is responsible for arithmetic and logic through the ALU, temporary storage through the registers and the movement of data along the buses. The control unit also responds to interrupts, signals from devices such as the keyboard requesting attention, so the processor can pause one task and handle the new request.

The control unit fetches, decodes and directs instructions.

It generates control signals but does not perform calculations.

The ALU performs the actual arithmetic and logic.

Registers hold operands and results during processing.

Interrupts let devices pause the CPU to request service.

ALU Operations and CPU Registers

The Arithmetic and Logic Unit (ALU) carries out all the calculations and comparisons the CPU needs. Its arithmetic operations include addition, subtraction, multiplication and division, while its logic operations include comparisons such as equal to, greater than and less than, plus the AND, OR and NOT operations used in digital circuits. When a program asks for 24 plus 18, the ALU performs the calculation and returns 42.

To work at full speed, the CPU keeps small high-speed storage areas called registers inside the processor. The Program Counter (PC) holds the address of the next instruction to be fetched. The Instruction Register (IR) stores the instruction currently being executed. The Memory Address Register (MAR) holds the address in memory that the CPU wants to read from or write to, and the Memory Data Register (MDR) holds the actual data being transferred between memory and the CPU.

Data moves through these registers during the machine cycle. The PC supplies the address of the next instruction, the address travels through the MAR to memory, and the fetched value arrives in the MDR and then in the IR. Registers are much faster than RAM because they sit directly on the processor chip, which is why the CPU uses them for its most frequent operations.

ALU arithmetic: add, subtract, multiply and divide.

ALU logic: compare values; AND, OR and NOT operations.

PC: address of the next instruction.

IR: the instruction currently being executed.

MAR: the memory address being accessed.

MDR: the data moving into or out of memory.

The System Bus Matrix

A bus is a set of parallel electrical pathways on the motherboard that carries information between the CPU, memory and devices. Because a complete system needs several kinds of information to travel at once, the computer uses a system bus made of three separate buses working together: the data bus, the address bus and the control bus.

The data bus carries the actual data being processed or stored. Its width, measured in bits (32-bit or 64-bit), states how many bits can travel side by side in one trip, so a 64-bit data bus moves twice as much data per transfer as a 32-bit bus. The address bus carries the memory addresses that the CPU wishes to access. Its width limits how much memory the CPU can use, because each combination of wires can represent one different address.

The control bus carries the command signals that coordinate the system. These signals tell memory and devices whether the CPU wants to read or write, and they carry the clock pulses that keep every part moving in step. Together, the three buses form the system bus matrix, the data highway that lets the CPU, RAM, ROM and input-output devices cooperate in a single coordinated machine.

Data bus: moves data; a wider bus transfers more at once.

Address bus: carries memory addresses; its width sets the memory limit.

Control bus: carries read and write commands plus clock signals.

The three buses together make up the system bus matrix.

Practical Work

1. Label a diagram of the system unit and the motherboard.
2. List the parts of the central processing unit and state the role of each.
3. Draw a table comparing RAM and ROM.
4. Trace how data travels along the system bus.

Scenario-Based Questions

1. A technician opens a desktop system unit and finds the CPU, RAM, graphics card, and storage drives all connected to one large circuit board. Name that board and explain why replacing it with a damaged board would stop the whole machine from working.
2. A student asks how the CPU manages to add 5 and 7. Using the ALU, the control unit, and registers, walk through the four steps of the machine cycle and state which part does each job.
3. A school is choosing new computers and the seller advertises a 64 bit data bus. Explain what the data bus carries, what a wider 64 bit bus means for data movement, and why the address bus and the control bus are also needed.
4. The lab assistant unplugs a computer in the middle of a lesson. The unsaved document vanishes, yet the startup instructions are still there when the machine is switched back on. Using RAM and ROM, explain the volatility of each and why this happens.
5. A student compares the motherboard to the central crossroads of a town. Using that comparison, trace what happens to a piece of data moving from the keyboard to the CPU and then out to the monitor, naming the pathway it travels along.
6. A phone repair workshop has two memory chips on the bench. One loses everything the moment power is removed; the other keeps its contents permanently. Identify which is RAM and which is ROM, and explain which chip must hold the boot instructions and why.
7. A technician explains that the CPU repeats the same four steps billions of times each second. Name those steps in order, and explain why this one repeated cycle is enough to handle both a lesson video and a drawn graph.

Learning Objectives

• Describe the keyboard and the mouse as input devices.
• Identify scanners, microphones, webcams and touchscreens.
• Choose the right input device for a task.
• Describe input technologies and assistive input devices.

The Keyboard and the Mouse

An input device is any hardware component that lets the user enter data and instructions into a computer. Input devices capture data in the real world (text, images, sound, movement) and convert it into digital signals that the CPU can process. The keyboard and mouse are the most common input devices.

The keyboard converts key presses into binary codes. Keys are grouped into the alphanumeric keys (letters, digits, and punctuation), the function keys (F1 to F12 across the top), the control keys (Ctrl, Alt, Shift, Enter, Backspace, Escape), the navigation keys (arrow keys, Home, End, Page Up, Page Down), and the numeric keypad. A typical QWERTY keyboard has 104 to 108 keys. The faster and more accurately a learner types, the more efficient school and office work becomes.

The mouse is a pointing device that controls the on-screen cursor. The basic actions are point (move the cursor to an item), click (select), double-click (open), right-click (show menu), drag (move an item), and scroll (move a page up or down). Modern mice are optical, using a light sensor instead of the rolling ball of older models. Some have a scroll wheel and extra buttons.

Scanners, Microphones, Webcams, and Touchscreens

A scanner captures printed text, photos, or documents and converts them into digital images that a computer can edit, store, and print. Flatbed scanners work like a photocopier, where the paper lies on a glass plate and a moving light passes over it. Scanner quality is measured in DPI (dots per inch). A higher DPI gives a sharper image but produces a larger file. Banks use scanners to digitise withdrawal forms, and schools scan report cards and certificates.

A microphone captures sound waves and converts them into digital audio signals. It is used for voice calls, voice notes, dictation, audio recording, and voice assistants. In the classroom, learners use microphones for presentations and for recording oral exercises in language lessons.

A webcam is a small digital video camera that captures moving images. It is built into most laptops and tablets or plugged into a desktop computer. Learners use webcams for virtual lessons, meetings, and video calls.

A touchscreen combines input and output in one panel. The screen displays output and also detects where the finger (or a stylus) touches, sending that position as input. Touchscreens are common on smartphones, tablets, bank ATMs, POS machines, and self-service kiosks. They can detect a single touch (like a tap), multi-touch gestures (like pinching to zoom), and in some cases pressure for drawing.

Choosing the Right Input Device

Choosing an input device depends on the type of data (text, numbers, sound, images), the speed and accuracy required, the environment (office, field, classroom), and cost. For typing a 20-page essay, the keyboard is best because it is fast and accurate for text. For digitising an old photograph, a scanner is best because it captures printed images exactly. For recording a meeting, a microphone is best because it captures sound for playback. For a video lesson with parents, a webcam is best because it captures moving images and voice. For checking a PIN at an ATM, a touchscreen or keypad is best because it is quick, simple, and secure.

Input devices vary in speed and accuracy. Touch typing on a keyboard is fast but needs practice. Scanning is highly accurate for paper. Microphone dictation is fast but can be affected by noise. Good ergonomics matter too, so learners should sit upright, keep wrists straight, take short breaks, and keep the screen at eye level. Poor posture with a keyboard and mouse causes pain over time.

Input Hardware Technologies

Input devices work by sensing physical signals and converting them into data the computer can process. An optical mouse uses a light sensor to track movement, a touchscreen detects where a finger touches, and a microphone converts sound waves into digital signals. Other technologies include magnetic input, which reads the strips on bank cards, and voice input, which turns spoken words into text or commands.

Optical: light sensors read movement or marks, as in optical mice and barcode readers.

Magnetic: card readers at banks and shops read magnetic strips on cards.

Touch: a touchscreen detects the position of a finger or stylus.

Voice and sound: a microphone converts sound waves into digital data.

In Nigeria these technologies appear in everyday life: a cashier scans barcodes optically, a customer pays by card read through a magnetic reader, and a commuter confirms a transfer on a touchscreen. Understanding the technology helps learners choose the right device and see that all input devices convert a sensed signal into binary.

Biometric input means input that uses a body feature such as a fingerprint.

Input Interfaces and Data Capture Techniques

An input interface is the point where a user or machine passes data into the system, including the physical port (such as USB or Bluetooth) and the software that receives the data. Data capture is the process of collecting data so the computer can store and use it. The keyboard captures typed characters, the scanner captures images as pixels, and the microphone captures sound as sampled values.

Interface: the physical port and software that connect a device to the system.

Manual capture: data entered by the user, as with a keyboard or mouse.

Automatic capture: data read without typing, as when a scanner reads a barcode.

Captured data is converted to binary before processing.

Automatic capture is especially useful in business. A courier scans a parcel barcode, a vendor reads a QR code to confirm a transfer, and a hospital captures patient details from an ID card. Good capture techniques reduce errors, save time and keep records accurate.

Alternative and Assistive Input Devices

Alternative input devices provide other ways of entering data for users who cannot use a standard keyboard or mouse comfortably. A joystick and a trackball replace the mouse, and a drawing tablet lets an artist write with a pen. Assistive devices help users with physical or sensory challenges, such as a screen reader that reads text aloud, voice recognition that converts speech to text, and head pointers or switches for users with limited hand use.

Joystick and trackball: alternatives to the mouse for moving the cursor.

Drawing tablet: a pen-based device for writing and drawing on screen.

Screen reader: software that reads on-screen text aloud.

Voice recognition: converts speech into text or commands.

Head pointers and switches: allow users with limited hand use to control the device.

The best input device is the one that lets each person work effectively. Considering accessibility when choosing devices makes technology fairer and ensures every learner can take part.

Practical Work

1. Group a list of input devices into typing, pointing and capturing devices.
2. Draw a table of five input devices and their uses.
3. Choose an input device for a bank and explain your choice.
4. Name two assistive input devices and who needs them.

Scenario-Based Questions

1. A bank wants to digitise ten years of paper withdrawal forms for its archive. Which input device should it choose, and why is that device better than typing every form with a keyboard, using speed and accuracy in your justification?
2. A teacher wants students at home to listen to a recorded listening test and then appear live for questions. Name the two input devices needed and explain what each one captures and turns into.
3. A hospital replaces a mouse and keyboard with a touchscreen in a self service kiosk where patients check in. Predict how the interaction changes, and give one advantage and one possible drawback of the touchscreen for that public setting.
4. A student must type a 20 page essay, and a school bookshop must digitise an old class photograph. Recommend the right input device for each task and justify both choices using the type of data and the accuracy required.
5. A reporter records voice notes at a busy market and later at a silent library, using dictation on a phone each time. Predict where the dictation will be more accurate, and explain how background noise affects microphone input quality.
6. An ATM is being redesigned, and the bank compares entering a PIN on a keyboard versus on a touchscreen. Which option does your note favour for speed and security, and what reasons does it give?
7. A learner wants to move a file from one folder into another on a desktop. List the mouse actions, and in what order, the learner would use to complete the move from the point action onwards.

Learning Objectives

• Describe monitors and soft copy output.
• Identify printers, speakers and projectors.
• Describe plotters and choose the right output device.
• Distinguish between soft copy and hard copy.

Monitors and Soft Copy

An output device presents the results of processing to the user. Output can be visual (text, images), audio (sound), or physical (printed paper). The monitor, printer, speakers, projector, and plotter are all output devices because they deliver processed information to humans.

The monitor is the main visual output device. It displays soft copy. Modern monitors are flat screens such as LCD and LED panels, while older models used bulky cathode-ray tubes (CRT). Screen quality depends on resolution (the number of pixels), refresh rate (how often the image updates), and colour range. A higher resolution, for example 1920 by 1080, shows sharper text and finer detail.

Soft copy is output presented on a screen, not printed. Hard copy is output printed on paper or another physical medium. The email PDF and the on-screen marksheet are soft copy. The printed paper is hard copy. Both are output from the same data.

Printers, Speakers, and Projectors

A printer produces hard copy. Two main technologies are common. Inkjet printers spray fine drops of ink onto paper. They are good at colour and cheap to buy, but slow and ink is costly. They are best for photos and posters. Laser printers use toner and a laser drum. They are fast, sharp, and cheap per page, but have an expensive initial cost. They are best for office documents and exams. Other printers include thermal printers (used for receipts in POS and banks) and dot-matrix printers (used for multi-part forms in some businesses).

Speakers and headphones convert digital audio into sound, the audio form of output. Schools use speakers for lessons and assemblies; headphone use helps learners avoid disturbing others in a computer lab.

A projector enlarges the computer screen and displays it on a wall or a projection screen. It is the clear choice for classrooms and presentations because many people can see the same content at once. A projector turns the computer's visual output into a large shared image.

Plotters and Choosing the Right Output Device

A plotter draws images using pens (or cutters) as it moves across paper, producing very precise, large drawings. It is used in architecture, engineering, and cartography for blueprints, maps, and circuit designs. Plotters are slower than printers for ordinary text but excel at line accuracy and continuous large-format output such as a 6-metre banner.

Choosing an output device depends on the audience (one person or many), the medium (screen, paper, sound), the quality needed, and the running cost. For daily class fact sheets, a laser printer is best because it is fast and cheap per page for text. For large business banners, a plotter or wide-format printer is best because it handles long continuous media. For teaching a class of 40, a projector is best because it provides one shared large image for everyone. For music during assembly, speakers are best because they provide wide audio reach. For photo prints for an event, an Inkjet printer is best because it has good colour reproduction.

Output Systems Overview

A computer processes data internally, but that work is only useful when it is presented to people in a form they can understand. The four main output systems are the monitor, the printer, the speaker and the projector.

The monitor presents soft copy output as text, images and video on a screen. The printer produces hard copy by printing text and images on paper.

The speaker converts digital audio into sound so people can hear music, speech and other audio content. The projector enlarges the image from the computer and throws it onto a wall or screen so many people can view it at once.

Choosing the right output system depends on the task. A report meant to be filed uses a printer, a presentation for a large audience uses a projector, and everyday work uses the monitor.

Printing Technologies

Impact printers strike a ribbon against the paper using physical force. Dot-matrix printers are the common impact type, still used where multi-part carbon forms are needed.

Non-impact printers form images without any physical striking. Inkjet printers spray tiny droplets of liquid ink onto the paper, producing rich colour. Laser printers use a beam of light and powdered toner to create sharp, fast text.

3D printing builds a physical object layer by layer from plastic, resin or metal. A 3D printer is an output device because it turns digital models into real three-dimensional objects.

DPI, dots per inch, describes how detailed a printed image is. PPM, pages per minute, measures how fast a printer works. These two figures let buyers compare printers.

Voice and Audio Output

Voice and audio output deliver information through sound. Speakers play music and announcements while headphones let one person listen privately. Voice output features read text aloud so users can receive information without looking at a screen.

Voice assistants like Google Assistant and Siri rely heavily on audio output. When you ask a question, the assistant answers with a spoken response generated from digital audio.

Audio output is also central to the entertainment industry. Video editors review soundtracks through studio monitors, and musicians mix their songs using speakers.

Industrial output describes how computers control physical machines. A CNC machine follows a computer program to cut, drill or carve materials with high precision.

An actuator is a component that converts an electrical signal from a computer into movement. Actuators power robotic arms, automated doors and conveyor belts.

Practical Work

1. Draw a table of five output devices and their uses.
2. Compare inkjet, laser and thermal printers.
3. Choose an output device for a large engineering drawing.
4. Explain the difference between soft copy and hard copy.

Scenario-Based Questions

1. A principal wants the whole school to watch a results presentation and also to hear the announcements. Which two output devices should the school set up, and what reasons from your note support each choice?
2. A school office must print 400 daily fact sheets every morning. Compare the inkjet and laser printers on buying cost, speed, and cost per page, then recommend one for the office with justification.
3. An architecture firm must print a precise six metre long building plan. Explain why a plotter is the better choice than an ordinary printer, and name what the plotter draws with.
4. A teacher emails a PDF of the timetable to parents instead of printing piles of paper. Distinguish soft copy and hard copy, and give one advantage of the soft copy and one advantage of keeping a hard copy in the office.
5. A graphic designer needs to print colour photos for an event, and a fuel station needs to print small receipts for customers. Identify the printer best suited to each task and justify each recommendation.
6. A student's monitor shows blurry text at low resolution. Explain which feature of the monitor controls sharpness of the display, and what the student should check when the school buys a replacement.
7. In a computer laboratory of 25 students, why would a school choose headphones rather than speakers for individual work, while choosing speakers for a whole school assembly? Justify both choices.

Learning Objectives

• Describe main memory, including RAM, ROM and cache.
• Identify secondary storage devices.
• Distinguish between memory and storage.
• Explain the memory hierarchy and the units of capacity.

Main Memory (RAM, ROM, and Cache)

Main memory is the working space of the computer, made up of chips the CPU can address directly. It exists in two main forms, RAM (Random Access Memory) and ROM (Read Only Memory). RAM is volatile, meaning it loses its contents when the computer is switched off. It holds running programs and data while the computer is on. ROM is non-volatile, meaning its contents remain even without power. It stores the boot and firmware instructions permanently.

The cache is a small, very fast memory placed between the CPU and RAM. It stores copies of frequently used data so the CPU does not have to wait for slower RAM. A bigger cache often makes a processor noticeably faster, which is why processor specifications advertise their cache size.

Today, 4 GB of RAM is enough for light school tasks, 8 GB suits general use with multiple apps, and 16 GB or more suits video editing and gaming. More RAM lets more programs run at the same time without slowing down.

Secondary Storage Devices

Secondary storage holds data and programs permanently, even when power is off. It is non-volatile. Four main families exist, namely magnetic storage (HDD), solid-state storage (SSD, flash), optical storage (CD, DVD, Blu-ray), and cloud storage managed on remote servers.

The hard disk drive (HDD) stores data on spinning magnetic platters. A read/write head hovers above the surface, like a record player needle but without touching. HDDs are cheap per gigabyte and come in large sizes (500 GB to many terabytes), making them ideal for desktops and backup drives. Their moving parts make them slower and more fragile than SSDs.

Solid state drives (SSDs) use flash memory with no moving parts. They are faster, quieter, cooler, and more shock-resistant than HDDs but cost more per gigabyte. A laptop with an SSD starts up in seconds, which is why most modern laptops ship with SSDs.

Optical discs (CD, DVD, Blu-ray) store data using laser-written pits on a plastic disc. A CD holds about 700 MB, a DVD holds 4.7 to 8.5 GB, and a Blu-ray disc holds 25 to 100 GB. Flash storage (USB flash drives, memory cards) uses flash memory chips and retains data without power. They are portable and convenient for file transfer.

Memory vs Storage and Capacity Units

Memory and storage are often confused, but they serve different purposes. Memory (RAM) holds data temporarily while the computer is running. Storage (HDD, SSD, flash) holds data permanently. A phone with 8 GB of RAM and 128 GB of storage uses the 8 GB for running apps and the 128 GB for storing photos, files, and apps.

Data is measured in units that get progressively larger. A bit is the smallest unit, a single 0 or 1. Eight bits make one byte, enough to store one character. A kilobyte (KB) is 1024 bytes, roughly half a page of text. A megabyte (MB) is 1024 KB, enough for a song or small photo. A gigabyte (GB) is 1024 MB, enough for a video or an app. A terabyte (TB) is 1024 GB, enough for hundreds of films. Each bigger unit is about 1024 of the previous one. Learners can estimate how many files fit by dividing one capacity by the other.

Choose storage by capacity (size of data), portability (do you carry it?), speed (do you run software from it?), and durability (rough travel?). For example, an operating system runs best from an SSD; film archives live best on a large HDD or cloud; everyday file transfer suits a flash drive.

Memory Hierarchy

A computer stores and moves data at different speeds and costs. The memory hierarchy organises storage from fastest and smallest at the top to slowest and largest at the bottom.

At the top are the registers, tiny and extremely fast storage built directly into the processor. Below that is cache, which is small and very fast, storing copies of frequently used data. Main memory (RAM) is larger but slower, holding programs and data in use. At the bottom is secondary storage (HDD, SSD, flash), which is slowest but holds data permanently.

Registers: fastest, built into the CPU

Cache: very fast, small, sits between the CPU and RAM

RAM: fast, moderate size, volatile

Secondary storage: slowest, largest, non-volatile

The faster the memory, the smaller its capacity and the higher its cost per byte. This is why computers use a hierarchy rather than one type of memory.

RAM versus ROM

RAM and ROM are both main memory but behave very differently. RAM (Random Access Memory) is volatile and read-write: it holds running programs and open files, and loses all data when the computer is switched off.

ROM (Read Only Memory) is non-volatile and read-only in normal use. It stores the startup instructions such as BIOS or UEFI firmware. Its contents are written once at the factory and survive power off.

A simple analogy: RAM is a whiteboard you write on during class; ROM is a printed card that never changes.

Cache Memory Levels

Modern processors use three levels of cache: L1, L2 and L3. L1 is the smallest and fastest, built into each core. L2 is larger and slightly slower, dedicated to each core. L3 is the largest and shared among all cores.

Cache speeds up processing through locality: programs tend to reuse the same data. When the CPU finds data in cache (a cache hit), it avoids the slower trip to main memory, making the system faster.

L1: 32 to 128 KB, fastest, one per core

L2: 256 KB to several MB, medium speed, one per core

L3: 4 to 32 MB, slowest cache, shared by all cores

Practical Work

1. Draw a table comparing RAM and ROM.
2. List three secondary storage devices and one use of each.
3. Explain why memory is called temporary storage.
4. Write the units of capacity from the bit upwards.

Scenario-Based Questions

1. A student buys a laptop advertised as 8 GB RAM and 256 GB SSD. Explain what each figure means, which is volatile and which is non-volatile, and why the laptop needs both to work.
2. A photographer stores photos of about 5 MB each. Using the capacity units in your note, estimate how many such photos fit on a 16 GB flash drive and how many fit on a 1 TB hard drive, showing the division you perform.
3. A technician must choose storage for two jobs: running the operating system for instant start up, and keeping years of film archives. Using the HDD and SSD, recommend the right device for each job and justify with speed, capacity, and cost per gigabyte.
4. A trader wants to carry business records between the shop and home every day, while a video editor needs to work on large projects without delay. Choose the most suitable storage for each person and justify your choices using portability and speed.
5. A student says my phone's 128 GB is what stores the sentence I am typing right now. Correct the confusion between memory and storage using RAM and the phone storage, and explain what the 128 GB truly holds.
6. A seller offers two nearly identical processors where one has more cache. Predict which processor runs noticeably faster, and explain where the cache sits and what it keeps for the CPU.
7. A school must send a 50 GB high definition film to another school. Using the capacities in your note, explain why a DVD cannot take it, and recommend which of the Blu-ray disc or the flash drive is suitable, justifying your choice.

Learning Objectives

• Distinguish between software and hardware.
• Describe system software and application software.
• Explain utility software, firmware and drivers.
• Describe the main types of software licence.

Software vs Hardware

Computer software is a collection of instructions, data, and programs that tell the hardware what to do. Hardware is the physical body of the computer; software is the mind that gives it purpose. Without software, hardware sits idle, and without hardware, software has nothing to run on.

Hardware is physical and can be touched. It wears out over time. It cannot be changed by the user easily. Examples include the CPU, keyboard, and monitor. Software is virtual and consists of instructions. It does not wear out but can become outdated. It can be installed, updated, and removed. Examples include Windows, Chrome, and MS Word.

Software is broadly classified into three main categories, namely system software, application software, and utility software.

System software is the most fundamental layer. It manages the computer's resources, provides a user interface, and allows application software to run. The most important system software is the operating system (OS). Application software is designed to help users perform specific tasks, such as word processors for creating documents, spreadsheets for handling numbers, web browsers for accessing the internet, and presentation software for creating slide shows.

Utility Software, Firmware, and Drivers

Utility software helps maintain, configure, optimise, or protect the computer. Common utilities include antivirus programs that detect and remove malware, disk cleanup tools that free up storage space, file compression tools that reduce file sizes for storage or transfer, backup utilities that create copies of important files, and disk defragmenters that reorganise data on a hard drive for faster access.

Firmware is a special type of software permanently stored inside a hardware device. It tells the device how to function at a basic level. Examples include the BIOS (Basic Input/Output System) in a computer motherboard, which controls the startup process, and the firmware in a printer that manages printing functions. Firmware can sometimes be updated to fix bugs or add new features.

A device driver is software that allows the operating system to communicate with a specific hardware device. Without the correct driver, the OS does not know how to control the device. For example, without a printer driver, the computer cannot send print jobs to the printer. Without a graphics card driver, the screen may display low resolution or lag.

Software Licensing

A software licence is a legal agreement between the software creator and the user. It defines how the software may be used, copied, and distributed. Different licences offer different rights.

Licensing protects both the creator and the user. Creators receive payment or recognition for their work. Users are protected by knowing what they are allowed to do with the software. Using proprietary software without paying for it (piracy) is illegal and unethical. Open-source software offers transparency because anyone can inspect the code for security or quality. In Nigeria, many schools use open-source software such as Linux and LibreOffice because it is free and reduces costs.

System Software Categories versus Application Software

System software is the set of programs that runs and manages the computer itself, while application software is the set of programs that users operate to perform specific tasks. This division helps users understand why a computer needs two very different kinds of software working together at the same time.

System software is divided into three main categories. The operating system (OS) controls the processor, memory, storage and input/output devices, and provides the interface users see. Utility software maintains and protects the system, such as antivirus programs and disk cleaners. Device drivers are the third category; each driver is a small program that lets the operating system speak with a specific piece of hardware such as a printer or a scanner.

Application software serves the user directly. Word processors such as Microsoft Word, spreadsheets such as Excel and browsers such as Chrome are all applications. A Nigerian bank clerk uses a banking application to record transactions, but every application depends on the operating system underneath to run.

The operating system manages hardware and provides the user interface.

Utility software maintains, optimises and protects the computer.

Device drivers connect the OS to individual hardware components.

Application software helps users carry out specific tasks such as typing, calculating or browsing.

Software Acquisition and Licence Types

Software reaches users through several channels. It can be bought as a boxed product, downloaded from the internet, bundled with new hardware or obtained as open-source code. Each method affects the licence under which the software is used.

Proprietary software is owned by a company that controls its use and distribution. Microsoft Windows and Adobe Photoshop are examples. Shareware is proprietary software distributed free for a trial period, after which the user is expected to pay. Freeware is proprietary software that is free to use but still closed, meaning the source code is not shared.

Open-source software publishes its source code so anyone can view, modify and distribute it. Linux, LibreOffice and Firefox are examples. In Nigeria, many schools save money by installing Linux and LibreOffice on their computer labs instead of purchasing proprietary equivalents.

Purchase and download are the two main ways to acquire commercial software.

Shareware allows free trial use before a mandatory payment or registration.

Freeware is free to use but the source code stays hidden.

Open-source software shares its code and is often free for schools to adopt.

How Software Controls Hardware

Software controls hardware through a chain of instructions that begins at the operating system and ends at the physical component. When a user presses a key, the key press reaches the CPU through the device driver, then the operating system decides which running application should receive it, and the application responds on the screen.

The operating system plays the central role in this chain. It allocates CPU time, reserves memory for each program, manages files on the disk and schedules when data is written to storage. Without the OS, applications would have no way to reach the hardware.

The interrupt system shows the OS at work. When hardware such as the mouse needs attention, it sends an interrupt signal to the CPU. The CPU pauses the current task and runs the OS handler for that device, then returns to the previous work. This is how a computer can type a document, play music and show a video at the same time.

Device drivers translate OS commands into signals that hardware understands.

The OS schedules tasks so every running program gets a fair share of the CPU.

Interrupts let hardware request CPU attention when data is ready.

Practical Work

1. Group a list of programs into system and application software.
2. Draw a table comparing system and application software.
3. Name three types of software licence and one rule of each.
4. Explain why a driver is needed for a printer.

Scenario-Based Questions

1. A cash-strapped school installs Linux and LibreOffice on all its computers. Identify the category of software each belongs to, and explain why the open-source licence makes this cheaper than Windows and Microsoft Office while still being legal.
2. After a system update, the school printer refuses to print and the operating system says it cannot control the printer. Predict the missing software and explain how a device driver lets the OS and the printer work together.
3. A student installs an antivirus program and a file compression tool on a school machine. Classify each as system, application, or utility software, and state exactly what each one does.
4. A software company wants to sell a product with secret source code, while a poor school needs the cheapest legal office programs. Compare proprietary and open-source software and justify a recommendation for the school.
5. A student downloads a pirated copy of Windows to avoid paying. Using the licensing rules in your note, explain why that is illegal and unethical, and name a legal alternative the school could use for the same class work.
6. An old desktop has no graphics card driver installed, so the display is blurry and slow, and there is also no audio driver. Using the driver table, predict what happens to the display and to the sound, and what the repair shop should install.
7. A school office wants to protect files from loss, free up disk space, and email smaller attachments. Name the three utilities in your note that do each job and explain why each is the right tool.

Learning Objectives

• State the role of the operating system.
• Describe file management and the types of interface.
• Explain the booting process.
• Name the main types of operating system.

Role of the Operating System

An operating system (OS) is system software that manages all the hardware and software resources of a computer. It acts as an intermediary between the user, the application software, and the physical hardware. Without an OS, every user would need to write instructions directly to each hardware device, which would be extremely difficult and inefficient.

The OS performs four main management functions, namely process management, memory management, file management, and device management. Think of the OS as the headmaster of a school. The headmaster does not teach every class directly, but assigns teachers (programs) to classrooms (memory), ensures the timetable (process scheduling) runs smoothly, manages the school's records (files), and makes sure the equipment (devices) is available when needed.

Process management involves deciding which program gets CPU time and for how long. Modern operating systems support multitasking, which means they can switch between processes so quickly that they appear to run at the same time, even on a single-core CPU.

Memory management involves allocating RAM to each running process and reclaiming it when the process finishes. If too many programs are running and RAM is full, the OS may use virtual memory, temporarily moving some data to the hard drive to free up RAM.

File Management, Interfaces, and Common Operating Systems

The OS organises data on storage devices using a file system. Files are stored in folders (directories) in a hierarchical structure. The OS keeps track of where each file is stored on the hard drive using a file allocation table or similar structure. It allows users to create, open, rename, move, and delete files through a file explorer or finder.

Most modern operating systems provide both a graphical user interface (GUI) for everyday tasks and a command-line interface (CLI) for advanced tasks. A GUI uses visual windows, icons, and menus that you can click. A CLI requires typing text commands. GUIs are easy for beginners, visual and intuitive. CLIs are faster for experienced users and use fewer resources.

Common desktop operating systems include Windows (Microsoft), macOS (Apple), and Linux (open-source). Common mobile operating systems include Android (Google) and iOS (Apple). Windows is used on most school and office computers. macOS is used on Apple Macs. Linux is used on servers, some schools, and by developers. Android is used on Samsung, Tecno, and Infinix phones. iOS is used on iPhones and iPads.

The Booting Process

When a computer is powered on, it follows a fixed sequence to load the operating system. First, electricity flows to the motherboard and components (power on). Second, the BIOS/UEFI firmware performs a Power-On Self-Test (POST) to check that hardware is working correctly. Third, the BIOS/UEFI locates the boot device (HDD or SSD) and loads the bootloader. Fourth, the bootloader loads the operating system kernel into RAM. Fifth, the kernel starts essential services such as the file system, network, and display. Sixth, the OS loads the desktop, login screen, or home screen.

If the POST finds a hardware problem, such as no keyboard or faulty RAM, it displays an error message or beep codes before the OS loads. A cold boot starts from completely off and performs a full POST and OS load. A warm boot restarts the computer and skips some checks for speed.

Booting means the process of starting a computer and loading the operating system.

The Functions of an Operating System

An operating system carries out five essential functions that together let a computer work safely and smoothly. It manages processes, memory, files and devices, and it also enforces security. Each function addresses a different resource, and the OS coordinates all of them at once.

Process management decides which running programme, called a process, gets the CPU's attention and for how long. Memory management allocates RAM to each running process so that every programme gets the space it needs, and reclaims the space when a process ends. File management organises data on storage devices using folders and a file system, so files can be saved, located and retrieved by name.

Device management controls the hardware connected to the computer, such as keyboards, printers and storage drives, by loading the correct drivers and passing data between the device and the running programmes. Security management protects the system from unauthorised access through user accounts, passwords and permissions, and it restricts what each user is allowed to do.

Process management, scheduling which programme uses the CPU and when.

Memory management, allocating and reclaiming RAM for running processes.

File management, organising, storing and retrieving data in folders.

Device management, controlling hardware through device drivers.

Security management, protecting the system with accounts, passwords and permissions.

Together these five functions are the reason the OS is described as a manager. It does not do the user's work directly, but it makes sure every part of the system does its own job at the right time, in the right order and in safety.

Types of Operating Systems

Operating systems are designed for different kinds of devices and different jobs. The main types are desktop operating systems, server operating systems, mobile operating systems and real-time operating systems.

Desktop operating systems run on personal computers, laptops and many school machines. The most common are Microsoft Windows, Apple macOS and the open-source Linux. Server operating systems run on server computers that serve many users at once, such as Linux distributions and Microsoft Windows Server, and they are built for reliability, security and running for long periods without restarts.

Mobile operating systems run on smartphones and tablets, and two dominate the Nigerian market, Google's Android, used on phones from brands such as Tecno, Infinix, Samsung and Nokia, and Apple's iOS, used on iPhone devices. Real-time operating systems respond to inputs within a fixed time limit, and they are used in machines that must react instantly, such as car braking systems, medical monitors and industrial machines.

Desktop OS, Windows, macOS and Linux for personal computers.

Server OS, Linux distributions and Windows Server for serving many users.

Mobile OS, Android and iOS for smartphones and tablets.

Real-time OS, used where the system must react within a fixed time, as in car brakes and medical monitors.

Choosing the right operating system depends on the job, and many Nigerian homes now hold several types at once, a Windows desktop for school work, an Android phone for browsing and a smart television with its own embedded system.

User Interfaces, CLI and GUI

A user interface is the part of the operating system a person talks to. Two families dominate, the command-line interface, CLI, where the user types text commands, and the graphical user interface, GUI, where the user clicks icons, buttons and menus.

The CLI is powerful, fast for repetitive tasks and uses very little memory, but the user must remember exact commands. The GUI is easier to learn because pictures replace commands, and it is the interface most everyday users prefer. Since Period 2 compared these two interfaces, this section looks at how they fit together in modern systems.

Modern desktop operating systems offer both. Windows provides the Explorer GUI alongside the Command Prompt and PowerShell, while macOS offers the Finder GUI with the Terminal, and most Linux systems rely heavily on the shell. Users move from the GUI to the CLI when they need precise control or automation.

Accessibility in Modern Interfaces

Accessibility means making the interface usable by people with different abilities. Modern operating systems provide features such as screen readers that speak the on-screen text aloud, high-contrast themes for low vision, magnifiers that enlarge parts of the screen, and speech recognition that turns a spoken word into typing.

For users with motor difficulties, the OS can slow the mouse speed, enable sticky keys that let one key be used one at a time, and accept eye or head tracking on some devices. Accessibility settings turn a standard computer into a tool nearly everyone can operate, and schools in Nigeria can enable these features free of charge on the machines they already own.

Screen readers speak on-screen text aloud for users with low vision.

High contrast and magnifier tools enlarge and clarify the display.

Speech recognition turns spoken words into typed text.

Sticky keys and slower mouse speeds help users with motor difficulties.

Accessibility is not a special extra; it is part of good operating system design, and these features benefit every user, such as when a learner reads text aloud or works with a small screen.

Practical Work

1. List five functions of an operating system.
2. Draw a table comparing a command line and a graphical interface.
3. Describe the steps that happen when a computer is switched on.
4. Name three operating systems and one device that uses each.

Scenario-Based Questions

1. A lab manager opens many programs at once until all the RAM is full. Predict what the operating system does to prevent a crash, and why the machine slows down, using memory management and virtual memory.
2. A beginner wants an easy machine, while a network engineer needs speed for repeated commands. Compare the GUI and the CLI and recommend the right interface for each person, justifying with ease of use and resources used.
3. A desktop beeps a pattern after power on and never reaches the desktop. Which boot step is failing, what does the beep code signal, and what should the technician check before the operating system even loads?
4. A parent wonders why a phone with Android behaves so differently from the school desktop running Windows. Compare the mobile and desktop operating systems, and state the four management functions they both perform.
5. Trace exactly what happens from pressing the power button to the desktop appearing, naming all six steps in order and the component involved in the Power-On Self-Test.
6. A single core CPU is asked to run Word, a browser, and a music player at the same time. Using process management and multitasking, explain why all three appear to run simultaneously.
7. A school on a small budget wants a free operating system used on servers and by developers. Recommend which type of operating system from your note to choose, and justify the choice by its developer and licence.

Learning Objectives

• State the uses of a word processor.
• Identify the parts of a word processing window.
• Create, save and close a document.
• Type, select and correct text in a document.

Uses of a Word Processor

A word processor is a program used to create, edit, format and print documents made mainly of text. It is used for letters, reports, assignments, minutes of meetings, brochures and examination files. Its advantage over a typewriter is that a change can be made after the text has been written, and the change appears in every copy that follows.

Other office tasks share the same programs. A spreadsheet calculates on numbers, a presentation program produces slides, and a database program stores linked records. A single office suite supplies several of these under one licence, which reduces the cost for a school.

Parts of the Window

The title bar shows the name of the open document. The quick access toolbar holds the commands used most often, such as save, undo and print. The ribbon holds the remaining commands under tabs named Home, Insert, Layout and Review.

The document area is the white page on which the text is typed. The ruler shows the margins and the indents. The status bar shows the page number, the word count and the zoom level. The scroll bar moves through a long document.

Word count can be applied to a selection, so counting only part of a document is possible and is often what is wanted.

Creating and Saving a Document

A new document is opened from the new command, or from a template when a particular style of document is required. Before typing, the margins, the orientation and the paper size are set from the layout tab, and the font, the size and the spacing are chosen.

Saving is done with the save command, which keeps the same name, and save as, which asks for a new name and a new folder. The document format uses the extension.docx. A document that must keep exactly the same layout on any computer is exported as a PDF.

Documents should be saved often and a backup kept in a second place. A document closed without saving loses everything typed since the last save.

A document saved only in memory is lost when the computer is switched off. Saving is what creates the file.

Typing, Selecting and Correcting

Text is typed at the insertion point, a blinking line that shows where the next character will appear. The enter key starts a new paragraph and the tab key indents. The space bar inserts a space, and the shift key combined with a letter gives a capital letter.

Selecting is done by dragging across the text, by clicking in the left margin beside a line, or with the keyboard. Shift and an arrow key extends a selection one character at a time, and control and A selects the whole document. A selection can then be cut, copied, replaced or formatted.

The spelling and grammar checkers underline doubtful words. Right clicking a suggestion accepts it, and ignoring a suggestion leaves it as it is. The thesaurus suggests another word with a similar meaning, and word count reports the length of the selection.

The enter key starts a new paragraph. The tab key indents the line, and it does not start a new paragraph.

Replacing text by typing over it destroys the original unless the selection was cut or copied first.

Practical Work

1. Create a new document, type a heading and three paragraphs, and save it as AssignmentOne.docx in your folder.
2. Use the ruler to set the left and right margins to 2.5 centimetres and record the result.
3. Select one paragraph, change the font, the size and the alignment, and record what you changed.
4. Use the thesaurus to replace two words with alternatives of a similar meaning.
5. Check the spelling of a paragraph and correct the flagged words.
6. Export the document as a PDF and confirm that the layout has not changed.

Scenario-Based Questions

1. A student typed four pages of work and closed the computer without saving. Explain what happened and how it could have been prevented.
2. Explain the difference between the enter key and the tab key when typing a document.
3. A document needs to be printed exactly as it appears on the screen on a computer in another school. Explain which format should be used.
4. Explain how to copy a paragraph from one place in a document to another without deleting the original.
5. Your friend says the spell checker proves a document is correct. Explain why this is not true.
6. Explain what a template saves a student who has to produce twenty reports of the same style.
7. Describe how to find the number of words in a selected paragraph only.

Learning Objectives

• Distinguish between machine, assembly and high-level languages.
• Explain the work of a compiler and an interpreter.
• Describe sequence, selection and iteration.
• Write a simple set of instructions in a high-level language.

Machine, Assembly, and High-Level Languages

Computers only understand binary (0s and 1s). Writing an entire program in binary would be extremely slow, error-prone, and impractical. Computer languages provide human-friendly ways to write instructions, and translation tools convert those instructions into the machine code the CPU needs.

Machine language (also called machine code) is the lowest-level language. It consists entirely of binary digits (0s and 1s) that the CPU can execute directly. Each type of CPU has its own specific machine language. Machine language is extremely fast because the CPU executes it directly, but it is nearly impossible for humans to write or read.

Assembly language replaces binary codes with short, human-readable mnemonics. For example, 'MOV A, 5' means move the value 5 into register A, and 'ADD A, B' means add the value in register B to register A. Assembly language is easier to write and read than machine code, but it is still closely tied to the specific CPU hardware. A program written in assembly for one type of processor may not work on another type.

High-level languages are designed to be close to human English. They use words like 'print', 'if', 'while', and 'input' to express logic. Examples include Python, Java, C++, JavaScript, and BASIC. High-level languages are portable, meaning the same code can run on different types of computers. However, they must be translated into machine code before the CPU can execute them.

Compilers, Interpreters, and Why We Program

A compiler reads the entire source code at once, checks it for errors, and translates it into machine code. The resulting machine code file (the executable) can then be run independently without the compiler. Compilers are used for languages such as C, C++, Java, and Pascal. They are efficient because the translation happens only once, but any error in the code means the entire program must be recompiled.

An interpreter reads the source code one line at a time, translates it, and executes it immediately before moving to the next line. If an error is found, the interpreter stops at that line. Interpreters are used for languages such as Python, JavaScript, and BASIC. They make debugging easier because errors are shown line by line, but the program runs more slowly because translation happens every time.

Programming is the process of writing instructions for a computer to follow. We program because computers can perform tasks far faster and more accurately than humans, but they need precise instructions. Programming allows us to automate repetitive tasks, create software and apps that solve real problems, build websites and digital services, control devices and robots, analyse large amounts of data, and develop games and educational tools.

A First Taste of Python

Python is a high-level, interpreted programming language created by Guido van Rossum in 1991. It is known for its simple, readable syntax that resembles English. Python is used in web development, data science, artificial intelligence, automation, education, and many other fields. It is an excellent first language for learners because of its clarity and wide availability.

The print() function displays text or values on the screen. Variables are named containers that store values. The assignment operator (=) puts a value into a variable. The input() function asks the user to type something and stores it in a variable. Python can perform calculations using standard math operators, such as + for addition, - for subtraction, * for multiplication, and / for division.

When a Python program runs, the Python interpreter reads each line, translates it into intermediate bytecode, and executes it. The bytecode is then processed by the Python virtual machine, which eventually sends instructions to the CPU in machine code form. The chain goes from source code (human-readable) to bytecode (intermediate) to machine code (CPU-executable).

Language Levels at a Glance

Computer languages are organised into levels showing how far they are from the binary instructions the processor understands and how close they are to human language. Machine language is the lowest level, made entirely of binary digits that the CPU executes directly. Assembly language uses short mnemonics such as ADD and MOV. High-level languages use English-like words and are easy for humans to read. Each level trades readability for control.

The three levels are linked to three translation tools. An assembler translates assembly language into machine code. A compiler translates a whole high-level program into machine code in one pass. An interpreter translates and runs a high-level program line by line. Compiled programs run quickly once built, while interpreted languages make debugging easier because errors are reported immediately at the exact line.

Algorithm Flow: Sequence, Selection and Iteration

Every program is built from three core structures. Sequence runs instructions one after another in order. Selection makes a choice using conditions such as if a score is above 50 then pass, otherwise try again. Iteration, also called looping, repeats a group of instructions until a condition is met. Together these three structures let a programmer express any algorithm that a computer can follow.

Programming Paradigms

A programming paradigm is a way of thinking about and structuring a program. Procedural programming arranges a program as a sequence of steps and reusable functions. Object-oriented programming, or OOP, organises a program around objects that hold both data and the actions that operate on that data. Functional programming treats computation as the evaluation of functions and avoids changing state. Each paradigm is a different tool, and many modern languages support more than one.

Practical Work

1. Group three languages by level and say why each is at that level.
2. Write two differences between a compiler and an interpreter.
3. Write the steps for a task as sequence, then add a selection and an iteration.
4. Write two lines in Python that print a greeting.

Scenario-Based Questions

1. A programmer says machine language is the fastest of all. Explain why that is true, and why a human would still prefer to write a high level language such as Python even though it needs translation.
2. A student's program has a bug on line 3. Which translator, a compiler or an interpreter, will show the error sooner and report it in a way that is easiest to fix? Justify your answer.
3. A developer is forced to run a large performance critical system on slow hardware, while another learner wants a small teaching script on a fast school PC. For each situation recommend a compiler-based or interpreter-based language and justify both choices.
4. A student writes print('Good day'), then name = input('What is your name? '), and then print(2 + 3). Explain what each line displays, and what the interpreter does with each line as the program runs.
5. An assembler sees the line MOV A, 5 and asks why the programmer does not write the binary directly. Compare machine language and assembly language, state the translator each needs, and explain why assembly written for one processor may not run on another.
6. A developer wants the same app to run on Android phones, office Windows PCs, and school Linux machines. Explain how a high level language is portable, and what must happen before each CPU can execute the translated code.
7. A trader wants a program that greets each customer by name. Using print(), input(), variables, and the assignment operator, describe the program the student would write and what happens on each line as the interpreter runs it.

Learning Objectives

• Revise all topics of the term.
• Consolidate the parts of the computer system.
• Practise questions on software, the operating system and word processing.
• Prepare for the end of term examination.

Review of the Computer System and History

A computer system has hardware, software and people that work together on data. Data enters as input, is processed, and leaves as output, and results may be stored. Data is a raw fact, while information is data arranged to give meaning.

The computer developed from early counting devices such as the abacus, through Babbage's Analytical Engine and Ada Lovelace's first program, to the electronic computers such as ENIAC. Later the transistor, the integrated circuit and the microprocessor made computers smaller, faster and cheaper.

The system unit holds the motherboard, the processor and the memory. The processor has the control unit, the arithmetic and logic unit and the registers, and these parts work together over the system bus.

Review of Devices, Memory and Software

Input devices enter data and output devices present results. Some output is soft copy on a screen and some is hard copy on paper. Memory is directly used by the processor, while storage holds data permanently, and capacity grows from the bit to the byte, the kilobyte, the megabyte, the gigabyte and the terabyte.

Software is either system software, which runs the computer, or application software, which helps the user do a task. The operating system manages the processor, the memory, the storage and the devices, and it provides the interface the user works with.

A word processor creates and edits text. Text can be typed, formatted and saved, and a document can be printed or sent.

Review of Languages and Programming

A computer language may be low level, such as machine or assembly language, or high level, close to English. A compiler translates a whole program, while an interpreter translates it line by line.

A program is an algorithm written in a language. Programs are built from sequence, selection and iteration, and a simple program can be written in a language such as Python.

Answering Examination Questions

Objective questions reward accuracy, so read every option before choosing. Short answer questions reward precision, so give exactly what is asked. In a difference question write both parts. In a list question number each item so that it can be marked.

Show working in any calculation, and label clearly in any diagram. Plan the last week of revision around the topics that were weakest in the class test.

Practical Work

1. Draw and label the parts of a computer system from memory.
2. Draw the table comparing RAM and ROM from memory.
3. List five functions of an operating system.
4. Write a simple three line program plan using sequence.

Scenario-Based Questions

1. Explain how you would revise ten weeks of work in four evenings.
2. Explain why reading notes once is a weak method of revision and give a better method.
3. A learner says memory and storage are the same thing. Explain the difference.
4. A learner says a compiler and an interpreter do the same job. Explain the difference.
5. Explain why a driver is needed before a printer will work.

Examination and Continuous Assessment Practice

These questions are taken from the First Term examination and Continuous Assessment papers for this class. Answer them in full sentences.

1. A designer is asked how a computer can hold a letter, a photograph and a song. Explain how a computer represents information, why the system uses only two symbols, and show how the letter A and the word CAT are stored.
2. (a) Trace the historical development of calculating devices by highlighting the contributions of the Abacus, John Napier, Blaise Pascal, and Charles Babbage. (b) Explain why Charles Babbage is regarded as the 'Father of Computers'. (c) Convert a storage measurement of 16 Megabits (Mb) into Megabytes (MB), recalling that 1 Byte = 8 bits. Show your workings.
3. (a) Tabulate the major technological components, advantages, and limitations of the First, Second, Third, and Fourth Generations of computers. (b) A legacy file system uses 2,048 Bytes of storage. Convert this value into Kilobytes (KB) and further convert it into bits. Show complete calculations.
4. (a) Classify computers based on operating principles (type) and explain each class with one example: Analog, Digital, and Hybrid. (b) Classify digital computers based on size and capability, describing Microcomputers, Minicomputers, Mainframe computers, and Supercomputers.
5. (a) Define Computer Hardware and categorize it into Input, Output, and Storage components. (b) Explain the primary functions of computer peripheral devices, giving specific attention to Scanners, Plotters, and Projectors. (c) Convert 10 Megabytes (MB) into Kilobytes (KB) and then calculate how many 512-byte blocks can fit into that 10 MB space.
6. (a) Differentiate clearly between Primary Memory and Secondary Storage, comparing RAM and ROM. (b) Perform the following storage scale conversions, showing all intermediate steps: (i) Convert 3 Gigabytes (GB) into Megabytes (MB). (ii) Convert 512 Bits into Bytes. (iii) Arrange the following storage capacities in descending order: 2 TB, 2,048 MB, 500 KB, 4,096 Bytes.
7. A school is about to buy a computer and a vendor claims that only the monitor and keyboard are needed. Explain the four components of a computer system, use the choir analogy to show how they fit together, and explain why the vendor's claim is wrong.
8. A shopkeeper in Lagos still uses a wooden frame with rods and beads, and a surveyor still carries a ruler with sliding scales. Name and describe the early calculating devices, and state who developed the Pascaline and what else the same person gave to modern computing.

Learning Objectives

• Answer every section of the examination paper.
• Complete the practical task accurately within the time allowed.
• Apply the conventions of classification and description.
• Analyse the result and plan the Second Term revision.

Before the Examination

Arrive early and confirm that the practical computers are working. Lay out two pens, a pencil, an eraser, a ruler and the identification card. Read the whole instruction sheet before touching the keyboard.

During the Written Paper

The paper will include objective questions that test single facts, names and classifications. It will also include short answer questions that test definitions, differences and short explanations.

Answer every question. Begin with the ones you are sure of. In a classification question, write the group before each item. In a list question, number the items so that each can be marked.

During the Practical Paper

Work in the order given. Create the file, enter the content, format it as instructed, then save with the exact name in the exact folder. Save at each stage rather than only at the end.

Check the finished file against the task before the time ends: the required document or worksheet exists, the required formatting has been applied, and the file name matches the instruction.

After the Examination

The marked script is analysed by counting the marks lost on each question. A question that most learners missed identifies a topic to reteught in the Second Term.

The Second Term begins with revision of the weak topics and then moves to new work, which continues with programming, databases and networks.

Practical Work

1. Read the whole instruction sheet before starting the practical task.
2. Note the required file name, folder, data and formatting before typing.
3. Save the file at each stage of the task.
4. Check the finished file against every item in the instruction before the time ends.
5. Note the topics that felt weakest for the Second Term revision plan.

Scenario-Based Questions

1. Explain why classification questions should be answered with the group written before the item.
2. Describe how you would check a finished word processed document against the practical instruction.
3. A candidate has ten minutes left and the file has not been saved. Explain the order of priorities.
4. Explain how the result of the examination is used to plan the Second Term work.
5. Explain why a file saved under the wrong name earns no marks in a practical examination.
6. Explain the difference between a short answer question and an essay question.
7. A difference question carries four marks and a candidate writes only one half. Explain how the marks are awarded.
8. ODELAMI

First Term Examination Practice Questions

These questions are taken from the First Term examination and Continuous Assessment papers for this class. Answer them in full sentences.

1. (a) Tabulate the major technological components, advantages, and limitations of the First, Second, Third, and Fourth Generations of computers. (b) A legacy file system uses 2,048 Bytes of storage. Convert this value into Kilobytes (KB) and further convert it into bits. Show complete calculations.
2. (a) Define Computer Science and Information and Communication Technology (ICT). (b) Distinguish clearly between Data and Information with two practical real-world examples of each. (c) If a text file contains 3,072 characters (assuming 1 character = 1 Byte), calculate its exact size in Kilobytes (KB). Show your step-by-step conversion.
3. (a) Trace the historical development of calculating devices by highlighting the contributions of the Abacus, John Napier, Blaise Pascal, and Charles Babbage. (b) Explain why Charles Babbage is regarded as the 'Father of Computers'. (c) Convert a storage measurement of 16 Megabits (Mb) into Megabytes (MB), recalling that 1 Byte = 8 bits. Show your workings.
4. (a) Classify computers based on operating principles (type) and explain each class with one example: Analog, Digital, and Hybrid. (b) Classify digital computers based on size and capability, describing Microcomputers, Minicomputers, Mainframe computers, and Supercomputers.
5. (a) Define Computer Hardware and categorize it into Input, Output, and Storage components. (b) Explain the primary functions of computer peripheral devices, giving specific attention to Scanners, Plotters, and Projectors. (c) Convert 10 Megabytes (MB) into Kilobytes (KB) and then calculate how many 512-byte blocks can fit into that 10 MB space.
6. (a) Differentiate clearly between Primary Memory and Secondary Storage, comparing RAM and ROM. (b) Perform the following storage scale conversions, showing all intermediate steps: (i) Convert 3 Gigabytes (GB) into Megabytes (MB). (ii) Convert 512 Bits into Bytes. (iii) Arrange the following storage capacities in descending order: 2 TB, 2,048 MB, 500 KB, 4,096 Bytes.