Grade 8 Computing Concept

 

Computer System

 

Computer system is an integration (combination) of hardware and software.

From the physical aspect, a computer system consists of :

a)      Input unit

b)      Processing unit including main memory

c)      Secondary storage

d)      Output unit

Which are controlled and managed by the system software.

 

Input – Data and instructions given by the user to the computer is referred as input

 

Input Unit/Devices – Input devices are the medium by which the user gives data and instructions to the computer.

Input devices converts input information to a suitable form acceptable to a computer.

Common examples of input devices are keyboard, mouse scanner etc.

 

Why does a computer need input devices?

Computer basically works on the input (data and instructions) given by the user so in order to receive data and instruction a computer needs input devices like keyboard etc.

 

Keyboard- It is an essential input device, the data and instructions are entered into the computers memory through keyboard.

 

Keyboard encoder- Keyboard encoder is a circuit that generates binary codes whenever a key is pressed on the keyboard. The binary code is sent to the computer.

Mouse – Mouse is an input device used for pointing, clicking and dragging icons etc.

 

Central Processing Unit- The function of CPU is to store the temporary current data and execute programs. The CPU also controls the operations of input and output devices and the memory. Under the control of CPU, data and programs are stored in the memory and displayed on the monitor (screen) or printed on the printer.

 

Major sections of CPU:

·         Arithmetic Logic Unit (ALU)

·         Primary Memory

·         Control Unit (CU)

 

Arithmetic Logic Unit: The Arithmetic Logic Unit (ALU) performs all the arithmetic and logical operations. The arithmetic computations include addition, subtraction, multiplication and division while logical operation includes comparisons.

 

Control Unit: It generates control signals necessary for the execution of instruction. In fact, it generates control signals which are necessary for the operations of different parts of the CPU, memory and  input/output (I/O)devices. It controls the entire operation of a computer.

 

Memory : A device for storing digital information that is fabricated by using integrated circuit technology. Also known as integrated-circuit memory; large-scale integrated memory; memory chip; semiconductor storage; transistor memory.

Semiconductor Memories- semiconductor memories are used as the main memory. They can be accessed randomly, so the access time taken is less and they are fast type of memory.

The semiconductor memories are classified into

a)      Random Access Memory (RAM)

b)      Read Only Memory (ROM)

 

Primary or main memory- The RAM and ROM are considered the primary memory of the computer system.

 

 RAM - Random Access Memory:

Random Access Memory (RAM)is the best known form of computer memory. The Read and write (R/W) memory of a computer is called RAM. The User can write information to it and read information from it.

The RAM is a volatile memory, it means information written to it can be accessed as long as power is on. As soon as the power is off, it can not be accessed. So RAM holds data and processing instructions temporarily until the CPU needs it.

 

Types of RAM

i)                   Static RAM (SRAM)

ii)                Dynamic RAM (DRAM)

 

ROM - Read Only Memory:       

Read only memory (ROM) is an example of nonvolatile memory.  ROM is a class of storage medium used in computers and other electronic devices. Read Only Memory (ROM), also known as firmware, is an integrated circuit programmed with specific data when it is manufactured. The instructions for starting the computer are housed on Read only memory chip.

 

Types of ROM :PROM,EPROM,EEPROM    

 

Differences between RAM and ROM:

·         A ROM chip does not require a constant source of power to retain the information stored on it, whereas a RAM chip does require a constant source of power to retain the information.

·         A user can read and write in RAM but can only read or access the contents of ROM.

 

Secondary/Backup/ Auxiliary Memory:

Secondary memory is used for storing large volumes of data. There are many different types of secondary memory that are being used.

The common backup storage used are:

·         Hard-disk / SSD

·         CD/DVD ROMs

·         Pen drive

 

Why do we need a backup memory?

The primary memory i.e. RAM of the computer is of volatile nature the data stored in RAM gets erased as soon as the power is switched off. So, in order to save data and information permanently backup up storage like hard disk, pen drive etc. are needed.

 

Differences between primary and secondary memory:

·  The primary memory is embedded with two types of memory technologies; they are the RAM (Random Access Memory) and ROM (Read Only Memory). The secondary memory is accessible in the form of Mass storage devices such as hard disk, memory chips, Pen drive, CD and DVD etc.

·  Primary memory RAM is volatile in nature, while  secondary memory is non volatile. The information of RAM cannot be retained when the power is turned off. In case of secondary memory, the information can be retrieved even if the power is turned off because the data will not be destructed until and unless the user erases it.

Output- The result of processed data is called as output which is often referred as information.

Output Unit/Devices- The output devices are the medium through which a computer displays the input data or generates the result of processing.

Example: Monitor, Printer, Speaker etc.

Processing – The systematic manipulation of data by the computer based on user’s instruction is called processing.

  

Computer Hardware and Software

Hardware- The physical components of a computer system are called hardware.

Common examples of hardware : Monitor, keyboard, Mouse, Printer etc.

Software- The set of programs that controls and manages the computer hardware and does various user assigned task is referred as software.

 

Types of software

1)      System Software (which includes)

i)                    Operating System

ii)                  Utility programs

iii)                Language processors

2)      Application Software

  

System Software- System software are the general programs written for the system which provide the environment to facilitate the writing of application software. In fact the software required to execute user’s program is known as system software.

 

Operating System- An operating system (OS) is an organized set or collection of software programs that controls the overall operation of the computer system.

Examples of operating system:

MS-DOS

WINDOWS-XP/7/8/10/11

Android/ IOs

UNIX

LINUX etc.

 

Functions of operating system:

a)      Supervision of the overall operation of the computer system

b)      Providing various support functions program to the user.

 

Utility Program- These are software tools which help users in developing, writing, debugging and documenting programs.

 

The utility program can be categorized into

a)      File management utilities- These are the programs to help the user in copying, erasing, renaming and printing files.

b)      Program development utilities- They are programs to help users to write and test programs

 

Language Processors- The programs which translates the program written in a programming language by the user into an executable program is known as language processor.

The program translated by the language processor is understood by the hardware of the computer.

Example of language processor are assembler, compiler and interpreter.

 

Assembler- A program which translates an assembly language program into machine language is called a assembler.

 

Compiler- A compiler is a program which translates a program written in a high level language into a language that can be understood by the computer. The compiler translates whole program at a time.

 

Interpreter- Interpreter is a program which translates the statement of a high level language into machine codes. It translates one statement at a time.

 

Application software- Application software are the programs used for solving or doing tasks of specific  (particular) nature.

Examples of application software:

a)      MS-WORD (WORD PROCESSOR)

b)      MS-EXCEL (SPREADSHEET)

c)      MS-ACCESS (DBMS)

 

Tailored made software- Tailor made software is software that is made to the specifications of a client. In other words it is custom made, bespoke, or 'tailored' to address a specific need.

Example : Result processing software for schools.

 

Packaged software- A packaged software is a generalized form of application programs meant for solving tasks of similar and varied nature for example MS-OFFICE it is a package containing word-processor, spreadsheet, database management etc.

 

Device drivers- A device driver is a software that allows to install and communicate with a piece of hardware. e.g. printer driver, sound card driver etc. 

 

 

Computer language:

An artificial language designed to convey instruction to a computer is known as a computer language.

Types of Programming languages:

1.  High level Programming Language (QBASIC)

2.  Middle level Programming Language (C )

3.  Low level programming Language ( Assembly Language)

4.  Machine Language ( instructions written using 0’s and 1’s)

 

High level language- The programming language that is independent of the computer hardware is referred as a high level language. High level language is problem oriented rather than computer oriented. The programmer does not need the knowledge of the architecture of the computer that is being used.

Examples of high level languages: BASIC, COBOL, PASCAL etc.

 

Advantages of high level language:

i)                    The programs written in one type of computer equally runs on the next i.e. the programs are portable.

ii)                  Programs of high level languages are easy to write modify and debug.

 

Classification of High Level Programming Language

a)      Scientific Language (PASCAL )

b)      Commercial Language (COBOL )

c)      Artificial Intelligence Language (LISP)

d)      Special Purpose Language (SNOBOL)

 

Low level language- A language in which each statement is directly translated into a single machine code is a low level language. Assembly language is an example of a low level language.

 

Assembly Language – A program written in mnemonics is known as assembly language program.

The meaningful and easily remember-able alphanumeric symbols are called mnemonics.

 

Machine Language- The language in which a computer works is called a machine language.

A program written in the form of 0’s and 1’s is called a machine language program.

 

Demerits of machine language program:

i)                    Program writing is difficult and tedious

ii)                  Chances of errors in writing programs are very high

iii)                 Debugging of errors in the program is difficult

iv)                 Program entry is slow.