Commonly Used Computer Terms 

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Hardware – Physical components e.g. monitor, keyboard, mouse, chips, wires, buses etc.

Software – Instructions, programs for specific tasks but they cannot be touched.

Firmware – Software replaced for hardware and stored in read-only memory as in BIOS.

Units of a computer system

  • Input Unit – Data is accepted from the user by it like keyboard, mouse etc.
  • Output Unit – Data output and feedback is given by it like printer, monitor etc.
  • Storage Unit – Stores data and results of processing like hard disk, optical disk, pen drive, etc.
  • Central Processing Unit – Both control unit and arithmetic logical unit are called CPU.
  • Arithmetic Logical Unit – It is responsible for arithmetic and logical computations.
  • Control Unit – It maintains order by controlling flow of information.

Representation of information

Data – It is meaningless and is raw fact as number, character etc. like count of items sold.

Information – It is meaningful and processed data like which product sells most.

Binary Number System – It uses two symbols to represent data, i.e. 0 and 1 and its base is 2.

Memory Size (Bit, Byte, KB, MB) –

Unit Equals   Unit Equals
1 Bit  0 or 1 1 KB  1024 bytes
1 Nibble  4 bits 1 MB  1024 KB
1 Byte  8 bits 1 GB  1024 MB

ASCII – Computer stores data in a coded form usually the American standard code for information technology (ASCII) is used, which can represent 256 different symbols by using 8 bits.

Basic Operations of a Computer – Input, Process and Output

  • Input – The process of entering the data and instruction to computer for processing.
  • Process – It refers to processing in CPU on the data, as per the given instructions.
  • Output – The process of output of the data from the computer system to user.

Input Devices

  • Keyboard – It is like a typewriter keyboard with 101 keys arranged in 5 groups as
  • Mouse – A pointing device used to position the pointer, to create graphics, for click and drag-and-drop. Ball or optical mouse is connected by PS/2 port or USB port to computer.
  • Scanners – It converts printed image to electronic form by using light.

Touch Screens and Voice Recognition Devices are also some other input devices.

Output Devices

Monitor – It is similar to television giving a soft copy output. Earlier monochrome or Colour CRT monitors were used but now LED & LCD.

Printers – It produces hard copy output on paper like laser or inkjet printers.

Storage Devices

It is consist of primary and secondary memory.

Primary Storage Devices – It is internal storage and consists of cache, ROM & RAM.

  • RAM (Random Access Memory) – It is read/write volatile memory storing temporary data in MB.
  • ROM (Read Only Memory) – It stores data permanently which can only be read like BIOS.
  • Cache – It is used for speeding up the data supply to CPU and stores frequently used data in KB.

Secondary Storage Devices – It is usually external storage and consists of disk and flash.

  • HardDiskDrive – It is used for mass storage with direct access.  It is non-volatile in sizes like 3.5”, 5.5” and 8”. It has disk platters on a spindle, with read/write head having 250-1024 GB capacity.
  • Optical Disk – Laser beam burns disk surface to write and low power reflected beam to read. It has speed rating or data transfer speed where 1X refers to 150 Kbps. CD-ROM and DVD are examples with 700 MB and 4.3 GB capacity. Blue ray is upcoming technology with 50 GB data.
  • Flash Memory – It uses semiconductor memory and is used in USB drives, memory cards, etc.

Data can be read or written to it and device can be detached to transfer or move data.

Central Processing Unit (C.P.U) – It executes given commands and is the mind of computer.

Types of Software

Software is instructions, programs to execute and it is classified as

System Software – It has direct interface with hardware Windows XP, Linux and consist of

Operating System Software – It controls the hardware and running of the application software like Linux, Windows XP/2003, MS-DOS. It does resource (CPU, memory) and task management with command interpretation (by a user interface graphical or character).

Application Software –It needs system software and it fulfill a specific user’s requirement like

  • Word Processing Software – It create and edit letters, reports, etc. like MS-Word
  • Spreadsheet Software – It store and process data in columns and rows like MS-Excel.
  • Presentation Graphics Software – It is used to create slides for presentations like MS-PowerPoint.

Disk Organization Terms

  • Boot Record – It is in the first sector of disk drive, from where the operating system is loaded into the memory when the computer is started.
  • Disk partitioning – Process of creating primary and extended partitions on disk drive.
  • File System – It is a way to organize data on storage device (hard disk) and like NTFS, FAT, etc
  • File Allocation Table (FAT) – It is a file system used by MS-DOS and MS-WINDOWS.


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