Wednesday, December 24, 2014

Functional units of computers P- 04. Information Communication Technology for Libraries

इस ब्लॉग्स को सृजन करने में आप सभी से सादर सुझाव आमंत्रित हैं , कृपया अपने सुझाव और प्रविष्टियाँ प्रेषित करे , इसका संपूर्ण कार्य क्षेत्र विश्व ज्ञान समुदाय हैं , जो सभी प्रतियोगियों के कॅरिअर निर्माण महत्त्वपूर्ण योगदान देगा ,आप अपने सुझाव इस मेल पत्ते पर भेज सकते हैं -

Functional units of computers

P- 04. Information Communication Technology for Libraries *

By :Usha Munshi,Paper Coordinator

Basic Operation of a Computer

The operation of a computer can be summarized as follows:
  • The computer accepts information in the form of programs and data through an input unit and stores it in memory.
  • Information stored in the memory is fetched, under program control, into an arithmetic and logic unit, where it is processed.
  • Processed information leaves the computer through an output unit.
  • All activities inside the machine are directed by the control unit. 
In order to carry out the operations, computer allocates the task between its various functional units. The computer system is divided into separate units for its operation. These are input unit, central processing unit, storage unit and output unit.

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Input Unit

The input unit accepts coded information from human operators or from other computers.
Examples: Keyboard, joystick, mouse, input pen, touch screen, trackball, scanner, bar code readers, microphone, floppy disks, magnetic tapes, compact disks.

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Memory Unit – Primary Storage

Primary Storage or Main Memory. This is where programs are stored during their execution. The Main memory is a fast memory capable of operating at electronic speeds.
Main Memory is also known as random-access memory (RAM). RAM is a memory in which any location can be reached in a short, fixed amount of time.
The memory unit divided into two:
  • Random Access Memory (RAM)
  • Read Only Memory(ROM)
Other versions of ROM are:
  • PROM(Programmable Read Only Memory)
  • EPROM.(Erasable Programmable Read Only Memory)

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    Memory Unit – Secondary Storage or Auxiliary Storage.
    This is used when large amounts of data have to be stored (on a more permanent basis), particularly if some of the data need not be accessed very frequently. This is a storage medium that will hold data and program/sets of instructions even if the computer system is switched off.
    Examples: Magnetic Disks (diskette, hard disk), Drums, Tapes, CDROMS, DVD-ROMS, Blue Rays, USB Flash Drives,  Hard disk nowadays has a capacity ranges from 200 GB – 1 TB.

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    Processing Unit

    It is also called the Central Processing Unit (CPU) or Central Processor.  The CPU is composed of the Arithmetic-Logic Unit (ALU) and the Control Unit (CU).
    The ALU is where all arithmetic and logic operations and manipulation of numbers take place. The CU is the nerve center of a computer. It controls the entire activity of the CPU. It controls and coordinates the order and execution of program instructions. It accesses instructions in sequence, interprets them and then directs their implementation.
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    Output Unit

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