Define the term computer?
A Computer is an automatic electronic apparatus for making calculations or controlling operations that are expressible in numerical or logical terms.
The Basic function performed by a computer is the execution of the program. A program is a sequence of instructions, which operates on data to perform certain tasks. In modern digital computers data is represented in binary form by using two symbols 0 and 1 which are called binary digits or bits. Computers use eight bits to represent a character internally. This allows up to 2(8) =256 different items to be represented uniquely. This collection of eight bits is called a byte. Thus, one byte is used to represent one character internally. One of the most common codes to represent characters in computer is ASCII
(American Standard Code for Information Interchange.)
Normally, a word may be equal to 8,16,32 or 64 bits. The terms like 32 bit computer, 64 bit computer etc. basically point to the word size of the computer.
Von Neumann proposed that there should be a unit performing arithmetic and logical operations on the data. This unit is termed as Arithmetic Logic Unit (ALU). A control unit directs the ALU to perform specific arithmetic and logical functions on the data.
A program is set of instruction consists of a sequence of steps.
The ALU and the CU together are termed as the central processing Unit (CPU). CPU is known as Brain of computer. The CPU is the most component of computer hardware. The ALU performs the arithmetic operations such as addition, subtraction, multiplication and division, and the logical operations.
All the arithmetic and logical operations are performed in the CPU in special storage areas called registers.
The size of the registers is one of the important considerations in determining the processing capabilities of the CPU. The larger the register size, the faster may be the speed of processing. A CPU’s processing power is measured in Million Instructions per Second (MIPS)
The instructions and data are to be supplied by external environment. Therefore, an input module is needed. Similarly, we need another component that will report the results in proper format and form.
This component is called output module.
It was pointed out by Von Neumann that the same memory can be used for storing data and instructions.
The memory unit stores all the information in a group of memory cells, also called memory locations, as the binary digits (bits). The amount of information that can be held in the main memory is known as memory capacity. The capacity of the main memory is measured in kilobytes (KB) or Megabytes(MB). One kilobyte stands for 2(10) kilobytes, which is approximately little over one million bytes.
A bus is a set of wires (lines) which you can visualize on the motherboard of a computer. It is a shared
media. A bus connecting the CPU, memory and I/O components is called a system bus. A system bus may
consist of 50 to 100 separate lines.
A CPU which includes a ALU and CU.
A main memory system
An Input/output System
The Von Neumann machine use stored program concept, i.e., the program and data are stored in the same
memory unit. A Von Neumann machine has only a single path between main memory and control unit
The Computer and Integrated circuit technology:
In an integrated circuit, the components such as transistors, resistors and conductors are fabricated on semiconductor material such as silicon. Hundreds or even thousands of transistors could be fabricated on a single wafer of silicon. An integrated circuit is constructed on a thin wafer of silicon that is divided into a matrix of small areas (size of the order of a few millimeters squares).
Initially, only a few gates were integrated reliably on a chip and then packaged. This initial integration was referred to as small-scale integration (SSI). The SSI gave way to Medium Scale Integration where 100s of gates were fabricated on a chip. Then came large Scale Integration (1000 gates) and very large integration (VLSI 100,000,000 components are expected to be fabricated on a single chip.
Semi conductor Memories:
Initially pace with electronics as more and more component were fabricated on single chip, fever chips are needed to construct a single processor. Intel in 1971 achieved the breakthrough of putting all the components on a single chip. The single chip processor is known as microprocessor. The Intel 4004 was the
Classification of Computers:
A microcomputers CPU is a microprocessor. The first microcomputers were built around 8 bit
microprocessor chips. The 8-bit Chip can retrieve instructions/data from storage, manipulate, and process an 8-bit data at a time or we can say that the chip has a built in 8 bit data transfer path. An improvement on 8-bit chip technology was seen in early 1980s, when a series of 16-bit chips namely 8086 and 8088 were introduced by Intel Corporation.
Minicomputer:The minicomputer is used as a multi-user system, which can be used by various users at the same time.
Gradually, the architectural requirement of minicomputers grew and a 32-bit minicomputer, which is called super mini, was introduced. Few of the popular mainframe series are IBM, HP, etc.
Mainframe computers are generally 32-bit machines or on the higher side. Mainframes are also used as central host computer to distributed systems. Libraries of applications programs developed for mainframe computers are much large than those of the micro or minicomputers because of their evolution over several decades as families of computing.
A commercial computer with vector instructions and pipelined floating point arithmetic operations is referred to as supercomputers. They are very powerful, high performance machines used mostly for scientific computations. A supercomputer is a computer best known for its high computational speed, fast and larger memory system and the extensive used for parallel processing.
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