Introduction to Computers



G P S Raghava
Bioinformatics Centre
Institute of Microbial Technology
Sector 39A, Chandigarh

History of Computers

The history of computers starts out about 2000 years ago, at the birth of the abacus, a wooden rack holding two horizontal wires with beads strung on them. Abacus is used in India, China and other Asian countries. Who invented and where invented is not known. In 1615, John Napier a Scottish mathematician developed a primitive form of slide rule known as "Napier bones" and used it to calculate first table of logarithms. The sliding rule, which is first analog calculating device, performs additions, substrations, multipications and divisions. It was blasé Pascal who invent the first digital machine in 1642. It added numbers entered with dials and was made to help his father, a tax collector.

In 1671, Gottfried Wilhelm von Leibniz invented a computer that was built in 1694. It could add, and multiply, after changing some things around. Leibniz invented a special stepped gear mechanism for introducing the addend digits, and this is still being used Thomas of Colmar created the first successful mechanical calculator that could add, subtract, multiply, and divide.

Charles Babbage around 1833, constructed 'Analytical' Engine which could store information, make decisions, and carry out instructions based on its decisions. The analytical engine was soon to use punched cards, which would be read into the machine from several different Reading Stations. The machine was supposed to operate automatically, by steam power. The tabulating Machine invented by Herman Hollerith was used in the Census of 1890 to speed up the process.

First Generation: First fully electronic computer was constructed by John P. Eckert and John W. Mauchly in 1946. It was called ENIAC. The size of ENIAC's numerical "word" was 10 decimal digits, and it could multiply two of these numbers at a rate of 300 per second, by finding the value of each product from a multiplication table stored in its memory. ENIAC was around 1,000 times faster then the previous generation of relay computers. It used 19,000 vacuum tubes, about 15000 square feet of floor space, and consumed about 180,000 watts of electrical power. It had punched card I/O, 1 multiplier, 1 divider/square rooter, and 20 adders using decimal ring counters, which served as adders and also as quick-access.

Second Generation: Invention of transistors made a revolution in computers. First computer was build using transistors in place of vaccume tube in 1958 by IBM. This was the break through that allowed computers to be faster, smaller, and cheaper. Transistors could perform up to 10,000 calculations per second. The transistors are the backbone of the second generation computers.

Third Generation: The third generation computers saw the replacement of transistors by integrated circuits. One IC could replace hundreds of transistors and perform millions of calculations per second. First computer of this generation was IBM370 built by IBM in 1964.

Fourth Generation/Microprocessor: Fourth generation computers saw the advent of the microprocessor. A microprocessor is an entire CPU on a single chip, and replaced many of the larger components of a computer. The microprocessor allowed the computer to find its way onto people's desk top. First microprocessor was built by INTEL 1971.


History of Personal Computers

The MITS Altair was the first 8080 based kit microcomputer. The Apple II was the first true "personal computer" it was factory built, in-expensive and easy to learn and use. Provided with the most extensive set of software and low cost floppy disks, the Apple II was also the first personal computer capable of color graphics and easy modem operation. Since 1981 IBM is dominating in market of personal computers (PC's). These PC's are based on Intel processors. In 1979, Intel introduced the 8086 and 8088 extensions to the 8080 product line. Since that time X86 product line has gone through six generations (popularly known as 386, 486 etc.). There is continues grow in power of the processor (4 MHz to 600 MHz clock; 8 bit to 64 bit database; 64k RAM to 256M RAM)



Computer Organization

Digital computers are electronic machines capable of performing high speed arithmetic/logical operations and data processing. It has two major parts i) computer hardware and ii) computer software. Computer hardware consists physical entities like electronics circuit, transistors, capacitors etc. Computer software is basically set of instruction code which instructs the computer to perform a task requested by user. Computer software consists of programs which monitor and coordinates all internal operations and provides easy interface between computer and user.

Computer hardware has four major parts i) Central processing unit (CPU); ii) Input unit; iii) Output unit and iv) Memory. The CPU in computer is similar to brain in human. It perform all the calculations, it execute all the instruction received from user. It also control activity of computer. Input devices provides the means to input to computer the computer. Following computer devices are commonly used by users i) Keyboard: consists array of key switches; ii) Mouse: it is a pointing device usually contain two or three button; iii) Joysticks: used to play games etc. Output devices are the means by which computer present its result in human readable form. Following computer output devices are commonly used by users i) Monitor/screen : displays data as text or in graphics ii) Printers: allow to print the data; iii) Plotters: used to plot the graphs

Storage devices are used to store and retrieve data in computers. Broadly, it can be classify in two categories i) primary storage and ii) secondary storage. Primary storage are semiconductor memories used access data quickly and randomly (e.g. RAM, ROM). Secondary storage also called Magnetic storage devices. These storage devices are cheaper and reliable (e.g. Floppy disk, Hard disk, Optical disk)

Operating Systems

Operating system (OS) manage the resources of computer and provide the interface between human and computer. Most OS appeared in the late 70's to the present time, varying from powerful multi-user OS's to little OS's that ran on 8 bit computers in under 64K of memory. To establish a point of reference, all computers must have an OS. The OS controls input and output; makes reasonable effort to control peripherals; and in short acts as the interface between you the user, the software, and the hardware.

Operating systems like UNIX and VAX/VMS were developed for powerful machines like workstations, mini and main frame computers. However, these operating systems are powerful but not suitable for small machine like PC. In order to fit on PC, 8-bit OS were developed like DOS, CP/M and Apple DOS. Windows which is extension of DOS is a powerful operating systems on PC's. It is user-friendly and provide graphics user interface.

Application Software Packages

Without software, computer literally have no use. Application program allow the user to perform /solve a specific data processing on computer. Popular software package on PC's are i) World for document preparation; ii) FoxPro for database management; iii) Harvard Graphics for drawing graphics; iv) Netscape for web browsing etc.

Programming Languages

In order to perform a task on computer one need to give instructions to computer. These set of instructions are called program. Computer understand only binary language (o and 1). Its practically difficult to write instruction in binary language. Programming of computers are similar to language like English, user write the program using these language. The programs are translated by compilers into to binary language which is computer readable.

Computer Networks

In computer network two or more computers are connected to each other so that they can exchange data and can share resources. Broadly, computer network can be classified into three categories i) Local Area Network (LAN); ii) Metropolitan Area Network (MAN) and iii) Wide Area Network (WAN). Network of computers in a local region like university, institute, organization is called LAN. Network of computers in cities which connect various universities, institutes come in category of MAN. A network which connect the computers across the cities, countries etc. called WAN. Internet come in category of WAN. In order to connect computers one need to have, some media (e.g. either net, radio-links, lease lines etc.) so that they can exchange data to each other, and common protocol (TCP/IP, Netbeui etc.).