History&comp.basics

HISTORY OF COMPUTERS It could rightly be called the first mechanical computing device. It

ABACUS

was used as far back as 2,600 B.C and is still used today. The first mechanical calculating machine that was developed by Blaise Pascal in the early 1600s. This device could add and

PASCALINE

subtract. Later Gottfried von Leibnitz developed a calculator that

AUTOMATED LOOM

DIFFERENCE ENGINE

ELECTROMECANICAL ENGINE

could also multiply and divide. This was invented by weaver Joseph Jacquered in LOOM the early 1800s that uses punched cards to record data. This is where modern computer history began. This machine was proposed by Charles Babbage in ENGINE the 1800s which bears the resemble of today’s computers which is capable of computing and at the same time print results. The American chapter of computer history began when Herman Hollerith successfully completed his tabulating machine for the Census Bureau in 1890. John Anatasoff is generally credited with building the first

ELECTRONIC COMPUTER

electronic computer as lowa State University. Was developed by Howard Aiken with the help of IBM, is the first

MARK I

large-scale, general-purpose, electromechanical computer. It was completed in 1994. This was the world’s first large-scale electronic digital computer

ENIAC

which was developed by J. Presper Eckert and John Mauchly in

EDSAC and EDVAC UNIVAC

1946. This computer is designed to calculate missile trajectories. Was later developed by mathematician John von Neuman in the 1940s which runs in the concept of stored programs. This is the first commercial computer which was completed and delivered to the U.S. Census Bureau in 1951.

MICROCOMPUTER BASICS

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The greatest application of digital circuits is in digital computers. A digital computer is a device that automatically processes data using digital techniques. Data are pieces of information. Processing refers to the variety of ways that data can be manipulated. Digital computers are classified by size and computing power. The largest computers are called Mainframes. These computers are expensive, having extensive memory and high-speed calculating capabilities. Smaller scale computers – the minicomputer and microcomputer – are more widely used. Even though they represent a small percentage of the total computer dollars invested, small-scale computers represent the largest number of computers in use. The Microcomputer is the smallest and least expensive of the digital computers that still retains all the features and characteristics of a computer.

Microcomputer

Mainframe

Minicomputer Computers are also classified by function. The most common function is data processing. Industry, business, and government use computers to maintain records, perform accounting tasks, keep inventory, and provide a wide variety of other data processing functions. Computers can be general purpose or special purpose. General-purpose computers are flexible and can be programmed for any task. Special-purpose, or dedicated, computers are designed to perform a single task. All digital computers consist of five basics blocks or sectors: control, arithmetic logic unit (ALU), memory, input, and output. In some cases the input and output blocks are a single block identified as input / output (I/O). Because the control unit and the arithmetic logic unit are closely related and difficult to separate, they may be collectively referred to as the central processing unit (CPU) or microprocessing unit (MPU).

INPUT

CONTROL

What is a Computer?

ARITHMETIC LOGIC UNIT (ALU)

MEMOR Y

OUTPUT 5

A computer is an electronic machine used to process information. However, we can do a whole lot more with computers than just calculate numbers or print out data. We can draw pictures, write memos and reports, and even communicate with other computer users. Educators can use the computer to write lesson plans, notices, letters, make visual aids, create presentations and share and collaborate with other teachers from around Uganda and the world. There are two basic parts of a computer: hardware and software. Hardware is a generic term for all the physical components of the computer. Software is a generic term for the programs that run on a computer.

Hardware Hardware is another term for the physical components of a computer. This is the most basic level on which the computer operates. The key point to remember is that all information is processed electronically. PC stands for Personal Computer, although that abbreviation is most often associated with computer running the Windows operating system. Below is a picture of a standard PC with each hardware part labeled. The photo on the right shows how the monitor, keyboard and mouse are connected to the System Unit.

Computer Hardware Parts

Back View of a System Unit How the hardware parts are connected

How a Computer Works 6

Input devices: Input devices give/enter information into the PC's System Unit. Common types of input devices are the following:

• • • • • • • • • • • •

Keyboard Mouse Trackball Joystick Scanners Digital Cameras Web cam Pen or Stylus Touch Screen Touch Pad Barcode Reader Card Reader

System Unit: Is the box which contains the CPU and RAM. It is where the information from the input devices gets processed. CPU (Central Processing Unit): Electronically processes the incoming information. The CPU is a complex microelectronic switch which evaluates the incoming signal and instructs other PC components to take certain actions. RAM (Random Access Memory): RAM is temporary electronic memory located inside the CPU that stores information. Output devices: The CPU sends signals to the output devices. The output devices then display the information. Common output devices are the following

• • • • • •

Monitor - the computers basic output device and produces the softcopy Printer - prints the softcopy and produces hardcopy Plotter - remarkably large printers for printing posters, blue prints, etc. Speakers - an audio output device Headphones LCD projector

Storage: A storage device is used to save a permanent copy of documents. Common types of storage devices include floppy disks and hard disks. You may also store data on zip disks and CD-ROMS.

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