Saturday, June 30, 2018

Difference in Regsters RAM DRAM SRAM ROM Cache & Flash Memory


  • Registers are parts of CPU with least capacity for storage. It is responsible for storing extremely limited amount of data & instructions instantly before and after processing 
  • Registers can use as lower 8 bits and higher 8 bit, means 16 bit or 32 bit registers.
  • Registers include accumulator, base index register, and count register and data known as General Purpose Registers.
  • They are used for I/O operations, counter loop etc.

RAM: (Random Access memory)

  • Its storage capacity is more than registers but less the secondary storage device.
  • It is temporary and volatile.
  • RAM chips lose their contents if current lost or turned off.
  • When we start most software programs the entire program is brought from secondary storage into RAM.
  • There are two main types of RAM.
  • DRAM or Dynamic RAM.
  • SRAM or Static RAM.


  • It stores the data in the form of an electric charge. This charge decreases time.
  • In order to maintain data in DRAM the chip is recharged or refreshed frequently.
  • During refreshing time computer cannot access DRAM.
  • This type of memory used in old microcomputers.


  • Memory cells are made of digital gates.
  • These gates can hold data without any need for frequent recharging.
  • SRAM is used in modern computers.

ROM: (Read Only Memory)

  • ROM is non-volatile memory and retains the instruction when the power to the computer turned off.
  • The instruction in ROM can only be read by the computer and cannot be changed by the user.
  • Vendor has written it.

There are several variations of ROM

  • PROM (Programmable read-only memory) consists of a blank chip on which the user can place data and programs.
  • EPROM (Erasable Programmable read-only memory): are similar to PROM but it can be erased and reprogrammed.
  • EEPROM (Electrically Erasable Programmable read-only memory): are similar to EPROM but it can be easier to erased and reprogrammed. It is most flexible type of ROM.

Cache Memory

  • High-speed memory that the processor can access more rapidly that main memory (RAM).
  • It stores blocks instructions used most often by the CPU.
  • Block instruction used less often remains in RAM and infrequently stored in storage devices.

There are two types of cache memory

  • L1 (level 1 cache) located in the processor.
  • L2 (level 2 cache) on the motherboard.

Flash Memory

  • Flash memory is a type of nonvolatile memory that can be erased electronically and rewritten, similar to EEPROM
  • Most computers use flash memory to hold their startup instruction because it allows the computer easily to update contents.
  • Flash memory also store data and programs on many mobile computer devices.

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