Digital Computers | Readstall

Digital Computers

05-02-19 Mounika Mayakuntla 0 comment

Digital computers:

                   Digital computer, digital implies the information in the computer represented by variables that take a limited number of discrete values. These values are processed internally by components that can maintain a limited number of discrete states. For example, the decimal digits 0,1,2,3,….9 provides 10 discrete values. It is a digital system that performs various computational tasks. The first electronic digital computers, developed in the late 1940’s, were used primarily for numerical computations. In this case the discrete elements are the digits. From this application the term digital computer has emerged. In practice, digital computer functions more reliably if only two states are used. Because of the physical restriction of components, and because human logic tends to be binary, digital components that are constrained to take discrete values are further constrained to take only two values and are said to be Binary.

Digital computers use the binary number system, which has two digits 0 and 1. A binary digit is called a bit. Information is represented in digital computers in groups of bits. By using various coding techniques, groups of bits can be made to represent not only binary numbers but also other discrete symbols, such as decimal digits or letters of the alphabet. By judicious use of binary arrangements and by using various coding techniques, the group of bits are used to develop complete sets of instructions for performing various types of computations.

In contrast, the common decimal numbers that employ the base 10 system, binary numbers use a base 2 system with two digits: 0 and 1. Consider an example of binary number: 1001011, it can be converted to a decimal number by multiplying each bit by the base 2 raised to an integer power. The seven bits 1001011 represent a binary number whose decimal equivalent is 75. Groups of bits in a digital computer are used to represent many different things. This is similar to the concept that the same letters of an alphabet are used to construct different languages, such as English and French.

The computer system is subdivided into two functional entities. They are Software and Hardware

Hardware: It consists of all the electronic components and electromechanical devices that comprise the physical entity of the device.

Software: It consists of the instructions and data that the computer manipulates to perform various data processing tasks.

Program: A sequence of instructions for the computer is called a Program.

Database: The data that are manipulated by the program constitute is the database.

Operating system: The programs include in a systems software package are referred to as the operating system.

Computer hardware:

The hardware of a computer usually divided into three major parts, as shown below.


Image result for block diagram of a digital computer



The CPU stands for Central Processing Unit contains an arithmetic and logic unit for manipulating data, a number of registers for storing data and control circuits for fetching and executing instructions. The memory of computer contains storage for instructions and data. It is called as Random Access Memory (RAM) because the CPU can access any location in memory at random and retrieve the binary information within a fixed interval of time. The input and output processor contains electronic circuits for communicating and controlling the transfer of information between the computer and the outside world. The input and output devices connected to the computer include keyboards, printers, terminals, magnetic disk drives, and other communication devices.

When  dealing with computer hardware it is customary to distinguish between what is referred to as computer organization, computer design and computer architecture.

Computer organization: It is concerned with the way the hardware components operate and the way they are connected together to form a computer system.

Computer design: It is concerned with the hardware design of the computer. Once the computer specifications are formulated, it is the task of the designer to develop hardware for the system. It is concerned with the determination of what hardware should be used and how the parts should be connected. This aspect of computer hardware is sometimes referred to as Computer implementation.

Computer architecture: It is concerned with the structure and behavior of the computer as seen by the user. It includes the information, formats, the instruction set and techniques for addressing memory.

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