Functioning of a Computer
Computer Performs four basic functions -which are as follows
Components of Computer
A computer consists of following main components
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Registers
These are special purpose and high speed temporary memory units. Registers are not referenced by their address, but are directly accessed and manipulated by the CPU during execution. Registers store data, instructions, address and intermediate results of processing. The number and size of more...
Computer Hardware
Computer hardware refers to the physical components of a computer that can be seen and touched by the user. By the use of these hardware devices, it made very easy for the computer for processing its data, store and retrieve. Hardware is one of the basic and necessary part of a computer system. Computer hardware also includes communication bus, ports, input devices, output devices, etc.
Input Devices
An input device can be defined as an electro mechanical device that allows the user to feed data into the computer for analysis and storage and to give commands to the computer. The data is entered into the main memory through the input devices. They accept instructions from the user and convert the accepted instructions into the machine language.
Some of the commonly used input devices are described below
Keyboard
It is one of the most common input devices. The user can type text and command using this device. The layout of the keyboard was borrowed from the regular typewriter with some additional keys. Keyboard is used to enter data or information in a computer system, which may be in numeric form or alphabetic form. When key is pressed, keyboard interacts with a keyboard controller and keyboard buffer. Keyboard controller stores the code of pressed key in keyboard buffer. There are different types of keyboard such as QWERTY, DVORAK and AZERTY.
Types of Keys on Keyboard
The keys are categorised under the following groups
(a) Alphanumeric Keys include the alphabet keys (A, B, C, ..., Z) and number keys (0, 1, 2, 3, .... 9).
(b) Numeric Keys are located at the right hand side of the keyboard. They consist of digits and mathematical operators.
(c) Function Keys are the programmable keys, i.e. the programs can assign some specific actions. They are numbered from F1 to F12.
(d) Cursor Control Keys include four directional (left, right, up, down) arrow keys that are arranged in a inverted T formation between the alphanumeric and numeric keypad. Above the arrow keys there are four more keys to control the cursor. These are as follows
Computer Memory
The computer memory is one of the most important elements in a computer system. It stores data and instructions required during the processing of data and output results. Storage may be required for a limited period of time, instantly or for an extended period of time. It also relates to many devices that are responsible for storing data on a temporary or a permanent basis.
Memory Hierarchy
The hierarchical arrangement of storage in current computer architectures is called the memory hierarchy. The computer uses a hierarchy of memory that is organised in a manner to enable the fastest speed and largest capacity of memory as shown in figure.
Parameters of Memory
Some related parameters of memory are as follow
(i) Storage Capacity It is representative of the size of memory. The capacity of internal memory and main memory can be expressed in terms of number of words or bytes.
(ii) Access Modes A memory is comprised of various memory locations. The information from these memory locations can be accessed randomly, sequentially and directly.
(iii) Access Time The access time is the time required between the desired modes for a read or write operation till the data is made available or written at the desired location.
(iv) Physical Characteristics In this respect, the devices can be categorised into four main categories as electronic, magnetic, mechanical and optical.
(v) Permanence of Storage Its permanence is high for future use in magnetic materials.
Types of Memory
In general, the memory is classified into two categories as follows
(a) Primary memory or Main memory
(b) Secondary memory or Auxiliary memory
Primary Memory
The memory unit that communicates directly with the CPU is called main memory or the internal memory. The primary memory allows the computer to store data for immediate manipulation and to keep track of what is currently being processed.
It is volatile in nature, it means that when the power is turned OFF, the contents of the primary memory are lost forever. Primary memory can be further classified in two categories which are as follows
Random Access Memory
It is also known as read/write memory that allows CPU to read as well as write data and instructions into it. RAM (Random Access Memory) is used for the temporary storage of input data, output data and intermediate results.
There are two categories of RAM as follows
(a) Dynamic RAM (DRAM) It is made up of memory cells where each cell is composed of one capacitor and one transistor. DRAM must be refreshed continually to store information. DRAM is slower, less expensive and occupies less space on the computer's motherboard.
(b) Static RAM (SRAM) It retains the data as long as power is provided to the memory chip. It needs not be refreshed periodically. SRAM uses multiple transistors for each memory cell. It does not use capacitor. more...
Data Representation
Data representation refers those methods which are used internally to represent information stored in a computer. Computers store lots of different types of information as numbers, text, graphics, sounds, etc.
Number System
It defines a set of values that is used to represent quantity. Digital computers internally use the binary number system to represent data and perform arithmetic calculations.
Types of Number System
The number systems generally used by a computer are as follows
Binary Number System
This system is very efficient for computers, but not for humans. It contains only two unique digits 0's and 1's. It is also known as Base 2 system. The binary numbers 0 and 1 are called a bit. The computer always calculates input in binary form. e.g. (10101 )2
Here, 2 represents base of binary number.
Computer Software
Software is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do. A software is a interface between the user and the computer. It is a set of instructions, programs that are used to give command to the hardware. It is responsible for controlling, integrating and managing the hardware components of a computer system and for accomplishing specific tasks.
Types of Software
Software can be divided into two major categories
System Software
It consists of several programs, which are directly responsible for controlling, integrating and managing the individual hardware components of a computer system. System software also provides the interface between the user and components of the computer. The purpose of system software is to insulate the applications programmer as much as possible from the detail of the particular complex computer being used. Depending on the functionality, the system software can be further divided into two major categories; system management program and system utilities.
System Management Program
It includes an integrated system of programs, which manages the operations of the processor, controls input/output, manages storage resources and provides various support services. Some common examples of system management programs are operating system and device drivers.
(a) Operating System It consists of programs, which control, coordinate and supervise the activities of the various components of a computer system. Its function is to provide link between the computer hardware and the user. Operating system performs all internal management functions (disk access, memory management, task scheduling and user interfacing) and ensures systematic functioning of a computer system. It provides an environment to run the programs, e.g. MS-DOS, Windows XP/2000/98, Unix, Linux, etc.
The operating system performs the following functions
Operating System
An operating system consists of a set of programs, which controls, coordinates and supervises the activities of the various components of a computer system. It is a program which acts as an interface between the user and the hardware. The interface enables a user to utilise hardware resources very efficiently. Operating system (OS) is an organised collection or intergrated set of specialised programs that controls the overall operations of a computer. It is a program that must be on any computer for proper booting.
Functions of Operating System
Operating system is a large and complex software consisting of several components. It is responsible for managing all the resources attached to a computer system.
Following functions are provided by an operating system to the convenience of users
Process Management
‘A Process is a program under execution'. It is the task which is currently being executed by the processor (CPU). The operating system handles the creation and deletion of processes and also manages the scheduling and synchronisation of process. Process management is the important part of an operating system which enables the activities of planning, monitoring and performance of a process.
Memory Management
Memory management of an operating system takes care of allocation and de-allocation of main memory to various processes. Managing the primary memory, sharing and minimising memory access time are the basic goals of the memory management. It also keeps track of memory usage. The performance of memory management is crucial for the performance of entire system.
File Management
File management module of operating system manages files held on various storage devices as well as transfers file from one storage device to another. The file management includes creating and deleting both files and directories, allocating space for files, keeping back-up, securing, easy access to files.
Input/Output Management
The Input/Output management module of the OS coordinates and assigns different input and output devices, namely terminals, printers, disk drives, tape drives, etc. Input/Output Management controls all I/O devices, keeps track of I/O requests, issues commands to these devices and takes measures which would ensure that data is transmitted efficiently and correctly to and from I/O devices.
Types of Operating System
The operating systems are classified as
Batch Processing Operating System
In batch processing operating system, a number of jobs are put together and executed as a group. This operating system is responsible for scheduling the jobs according to priority and the resource required. It is the type of OS which does not interact with the computer directly, e.g. Unix.
Single User Operating System
It is a type of operating system which allows only one user at a time. Operating system for personal computer (PC) is single user OS. They are designed to manage one task at a time. e.g. MS-DOS, Windows 9X.
Multi User Operating System
This OS allows multiple users to access a computer system concurrently. It is used in computer more...
Programming Concepts
It is the sequence of instructions in which the problems of computer tasks and steps are performed with the help of computer. A person who writes or performs the program is known as programmer. Programmer uses some specific languages to write program which is known as programming languages e.g. C++, Java, etc.
Programming Language
It is a set of keywords, symbols and a system of rules for constructing statements by which humans can communicate instructions to be executed by a computer.
Programming languages are mainly categorised into three parts which are as follows
Low Level Language
These programming languages are more arcane and difficult to understand. It is designed to operate and handle the entire instruction set of a computer system directly which are generally used to write the system software, e.g. Machine language and Assembly language.
Machine Language
It is the only language understood by the computers. Sometimes, it referred to as machine code or object code or binary language. It is a collection of binary digits (0 or 1) or bits that the computer reads and interprets.
Assembly Language
It is a low level programming language which is used as an interface with computer hardwares. It uses structured commands as substitutions for numbers, allowing humans to read the code easier than looking at binary codes.
Medium Level Language
It serves as the bridge between raw hardware and programming layer of a computer system. It is designed to improve the translated code before it is executed by the processor. C language is known as medium level language.
High Level Language (HLL)
It is an advanced computer programming language that is not limited to one computer, designed for a specific job and is easier to understand. The main advantage of high level languages over low level languages is that they are easier to read, write and understand, e.g. BASIC, C, FORTRAN, Java, Pascal, etc.
Some High Level Languages and Their Application Areas
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(v) Ruler It appears on the top of the document window. It allows to format the horizontal or vertical alignment of text in a document.
There are two types of rulers
(a) Horizontal
