Information Technology and Systems
Chapter 1 : Computer Systems - An Overview
Evolution of Computer Systems
Generations of Computers
First Generation Computers (1940-56)
Second Generation Computers (1956-63)
Third Generation Computers (1963-71
Fourth Generation Computers (1971-91)
Fifth Generation Computers (1991 and Beyond)
Organization of Computer Systems
Input Unit
Central Processing Unit
Processors
Output Unit
Storage Unit
Categories of Computers
Classification Based on Purpose
Classification Based on Technology Used
According to Size and Capacity
Peripheral Devices
Input Devices
Output Devices
Memory and Storage Devices
Overview of Hardware and Software
Interaction between Hardware and Software
Chapter Summary
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Computers have become an integral part of our society irrespective of the
field of work. The history of computer development can be explained in terms
of five generations of computers, namely, the first generation computers
(1940-1956), the second generation computers (1956-63), the third generation
computers (1963-71), the fourth generation computers (1971-91), and the
fifth generation computers (1991 and beyond). These generations are
characterized by various technological developments that have transformed
the ways in which computers operate. Over the years, the computers have
become smaller in size, less expensive, more powerful and efficient, and
reliable.
A computer follows the instructions given by the program while it performs
the four basic operations of Input, Processing, Output, and Storage. The
keyboard, the mouse, the microphone, etc., are the input devices which are
used to enter data and instructions into the computer for processing the
required information. |
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The Central Processing Unit (CPU) carries out the processing function of the
computer; in this process, the CPU uses the Random-Access Memory (RAM).
Monitors, speakers, printers, etc., are output devices through which the
final computed or processed information can be obtained. The data,
instructions, and the final processed information can be stored on the hard
disks, floppy disks, CD-ROMs, USB pen drives, and other additional devices.
The Control Unit (CU) and the Arithmetic Logic Unit (ALU) are the two
components of the CPU. The CU performs the four basic operations of:
obtaining the instructions from the memory of the computer, decoding the
instruction, executing the instruction, and writing the results onto the
memory. The ALU performs arithmetic and logical operations on the data.
Computers can be broadly classified on the basis of their utility,
technology, size, and capacity. According to purpose, computers are
classified into general purpose computers and special purpose computers.
According to technology used, computers are classified into analog
computers, digital computers, and hybrid computers. According to size and
capacity, computers are classified into supercomputers, mainframes,
minicomputers, microcomputers, and servers.
Peripheral devices are devices that are attached to a computer system which
augment the basic services provided by it. These can be the input devices,
output devices, or various auxiliary storage units of a computer system.
Computer hardware refers to all the physical devices in the computer like
the CPU, the monitor, and the printer that can be physically felt. Computer
software consists of the programs that instruct the computer hardware. Both
the hardware and software of a computer complement each other and should
work together to produce useful output.
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Short Case Studies / Caselets