Thursday, 23 February 2017

Organization of Computer System


There are 5 main computer components that are given below:
  • Input Devices
  • CPU
  • Output Devices
  • Primary Memory
  • Secondary Memory


The operations of computer components are given below:
1) Inputting: It is the process of entering raw data, instructions and information into the computer. It is performed with the help of input devices.
2) Storing: The computer has primary memory and secondary storage to store data and instructions. It stores the data before sending it to CPU for processing and also stores the processed data before displaying it as output.
3) Processing: It is the process of converting the raw data into useful information. This process is performed by the CPU of the computer. It takes the raw data from storage, processes it and then sends back the processed data to storage.
4) Outputting: It is the process of presenting the processed data through output devices like monitor, printer and speakers.
5) Controlling: This operation is performed by the control unit that is part of CPU. The control unit ensures that all basic operations are executed in a right manner and sequence.

CPU

  • A central processing unit (CPU) is an important part of almost every computer. The CPU sends signals to control the other parts of the computer, almost like how a brain controls a body.
  •   The CPU is an electronic machine that works on a list of things to do, called 'instructions'. It reads the list of instructions and does (executes) each one in order. A list of instructions that a CPU can run is a computer program.
  •  The speed that a CPU works at is measured in hertz (Hz). Modern processors often run so fast that gigahertz (GHz) is used instead, which means a billion cycles per second.
  •  When the CPU runs a computer program, it needs somewhere to store the data that the instructions operate on (the data that they read and write). This storage is called a register. A CPU usually has many registers. Registers must be very fast to access (to read and write). Therefore they are part of the CPU chip itself.
  •  CPU performance also depends upon the RAM, bus speed and cache size as well.

COMPUTER MEMORY

Memory is an essential element of a computer. Without its memory, a computer is of hardly any use. Memory plays an important role in saving and retrieving data. The performance of the computer system depends upon the size of the memory. Memory is of following types:

 

Primary Memory

Primary Memory is of two types: RAM and ROM.

RAM (Volatile Memory)

It is a volatile memory. It means it does not store data or instructions permanently. When you switch on the computer the data and instructions from the hard disk are stored in RAM.
CPU utilizes this data to perform the required tasks. As soon as you shut down the computer the RAM loses all the data.

Types of RAM

DRAM (Dynamic Random Access Memory)

DRAM stands for Dynamic Random Access Memory. It is used in most of the computers. It is the least expensive kind of RAM. It requires an electric current to maintain its electrical state. The electrical charge of DRAM decreases with time that may result in loss of DATA. DRAM is recharged or refreshed again and again to maintain its data. The processor cannot access the data of DRAM when it is being refreshed. That is why it is slow.

SRAM (Static Random Access Memory)

SRAM stands for Static Random Access Memory. It can store data without any need of frequent recharging. CPU does not need to wait to access data from SRAM during processing. That is why it is faster than DRAM. It utilizes less power than DRAM. SRAM is more expensive as compared to DRAM. It is normally used to build a very fast memory known as cache memory.

MRAM (Magneto resistive Random Access Memory)

MRAM stands for Magneto resistive Random Access Memory. It stores data using magnetic charges instead of electrical charges. MRAM uses far less power than other RAM technologies so it is ideal for portable devices. It also has greater storage capacity. It has faster access time than RAM. It retains its contents when the power is removed from computer.

Different between SRAM and DRAM

SRAM

  • It is faster than DRAM.
  • It is more expensive as compared to DRAM.
  • It does not need to be power – refreshed.
  • It utilizes less power.
  • It holds data indefinitely as long as the computer is turned on.
  • It is more complex and less compact.

DRAM

  • It is slower than SRAM.
  • It is less expensive.
  • It has to be refreshed after each read operation.
  • It utilizes more power.
  • It holds data dynamically not indefinitely.
  • It is less complex and more compact.

ROM (Non-volatile Memory)

It is a non-volatile memory. It means it does not lose its data or programs that are written on it at the time of manufacture. So it is a permanent memory that contains all important data and instructions needed to perform important tasks like the boot process.

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