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: BY THE END OF THE LESSON STUDENTS SHOULD BE ABLE TO:

Rationale: A computer system is a complete, functional unit that combines physical hardware, software instructions, data, and the people who operate it. Understanding what is a Computer System?, the Input-Process-Output (IPO) Model, role of the CPU, data vs Information helps learners use digital technology confidently, safely and responsibly.

Pre-requisite Knowledge: Learners have just entered SS 1 and already use digital devices such as phones, radios, televisions and computers at home or in the community. They can switch a device on, make a call, send a message and identify common parts such as the screen, keyboard and mouse.

Learning Material/Teaching Aid: Whiteboard, markers, computer or laptop where available, printed notes and charts on Computer Systems and Digital Technologies, practical task sheets, learners' notebooks and pens.

Reference Materials: Digital Technology for Senior Secondary Schools (SS 1); NERDC Digital Technology Curriculum; Digital Technology SS 1 First Term Notes (Week 1); First Term examination and Continuous Assessment question papers.

LESSON DEVELOPMENT

Assignment: i. A point-of-sale terminal reads a card, a shop scans a barcode, and a learner uses a screen reader to work without sight. Explain the technologies used in input hardware, explain input interfaces and data capture, and name the alternative and assistive devices. ii. 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.