JSS 2 First Term

Learning Objectives

• Define a computer and state its main characteristics.
• Name the early computing devices in order.
• Describe the five generations of computers.
• Classify computers by size, purpose and technology.

What is a Computer

A computer is an electronic device that accepts data, processes it according to a set of instructions called a program, and produces useful output called information. The word computer comes from compute, which means to calculate.

Modern computers do far more than calculate. They store photographs, play music, send messages and control machines. Their main characteristics are speed, accuracy, storage ability, automation and versatility.

A computer is more flexible than a calculator. A calculator does only arithmetic, while a computer can be programmed to do many different jobs.

Early Computing Devices

The abacus is one of the oldest counting devices. Beads slide on rods to stand for numbers, and it was used in China, Greece and Rome long before calculators existed.

In 1617 John Napier invented Napier's Bones, a set of numbered rods that made multiplication and division faster.

In 1642 Blaise Pascal built the Pascaline, a machine with gears that could add and subtract.

In 1801 Joseph Jacquard built a loom controlled by punched cards. The idea that a card could carry instructions was later used in computers.

In the 1820s Charles Babbage designed the Difference Engine to calculate mathematical tables. He then designed the Analytical Engine, which had a store for data and a mill for processing, and it is regarded as the first design for a programmable computer. Ada Lovelace wrote instructions for it and is called the first computer programmer.

The First Electronic Computers

The first electronic computers appeared in the 1940s. ENIAC, the Electronic Numerical Integrator and Computer, was built in the United States and used about seventeen thousand vacuum tubes. It weighed about twenty seven tonnes and filled a room, yet could perform about five thousand additions each second.

UNIVAC, the Universal Automatic Computer, was delivered in 1951 and was the first electronic computer sold commercially.

Generations of Computers

A generation is a major stage in the development of computers, marked by a change in the main technology.

The first generation used vacuum tubes, with ENIAC and UNIVAC I as examples. The second generation used transistors, which were smaller and more reliable, with the IBM 1401 as an example. The third generation used integrated circuits, with the IBM System/360 as an example. The fourth generation used microprocessors, which made the personal computer possible. The fifth generation uses artificial intelligence.

Each generation made computers smaller, faster, cheaper and more reliable than the one before.

Classification of Computers

Classification means grouping things together because they share similar features. Computers are classified by size, by purpose and by technology.

By size, a supercomputer is the fastest and largest, used for weather forecasting and scientific research. A mainframe handles many users at once, such as a bank processing transactions. A minicomputer serves a small group, such as a department in a university. A microcomputer is for one user and includes desktops, laptops and tablets.

By purpose, a general purpose computer can do many different jobs, while a special purpose computer is built to do one job only, such as an automated teller machine or a traffic light controller.

By technology, an analogue computer works with continuous quantities, such as the needle of a speedometer. A digital computer works with the digits 0 and 1. A hybrid computer combines both, as a hospital monitor does when it measures a heart rate and shows a digital reading.

Practical Work

1. Draw a timeline showing the abacus, the Pascaline, the Analytical Engine, ENIAC and a modern laptop.
2. Make a table classifying five computers by size, purpose and technology.
3. Write two differences between an analogue device and a digital device.
4. State the main technology used in each of the five generations of computers.

Scenario-Based Questions

1. A government office in 1970 buys a computer the size of a room that can only do basic calculations. Explain, using the generations, why the older computer was so large and limited.
2. A science museum displays a replica of the CDC 6600 built in 1964. A visitor asks who invented the supercomputer. Using Seymour Cray and Phillip Emeagwali, how would you answer?
3. A school needs a computer for one teacher to type lesson plans and mark exams. Which classification by size and by purpose fits best, and why?
4. A hospital uses a device that measures a patient's heart rate continuously and displays a digital reading. Is it analogue, digital or hybrid? Explain.
5. A car speedometer shows speed by moving a needle along a scale. Why is it classified as an analogue device rather than a digital one?
6. A student types assignments and browses the internet at home. Classify the computer by size, purpose and technology, giving a reason for each answer.
7. A factory uses a machine that adjusts speed from sensor readings but also has a manual dial. What type of technology does it use?