Anatomy of a Digital Computer: Memory Unit and Secondary Storage

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Computer architecture image

Computer Architecture Image

Memory Unit

Capacity of Primary Memory

Memory Unit Image

Memory Unit Image

1.Random Access Memory (RAM)

Random Access Memory(RAM) image

Random Access Memory(RAM) Image

  • It is also called read/write memory

  • RAM is the most common type of memory found in computers and other devices, such as printers

2. Read Only Memory (ROM)

Read Only Memory (ROM) Image

Read Only Memory (ROM)

  • The storage of program and data in the ROM is permanent.

  • ROM is non-volatile memory


  • There is another type of primary memory in computer, which is called Programmable Read Only Memory (PROM).

  • It cannot be changed and remain intact even if power is switched off.


  • This stands for Erasable Programmable Read Only Memory, which overcome the problem of PROM and ROM.

  • When the EPROM is in use, information can only be read.


  • This stands for Electrically Alterable Programmable Read Only Memory.

  • The only difference is that the memory can be altered using electrical signals

6. Cache Memory

  • The speed of CPU is extremely high compared to the access time of main memory.

  • It is also very expensive to have bigger size of cache memory.

  • Its size is therefore, normally kept small.

7. Registers

  • The CPU processes data and instruction with high speed.

  • So, the computer uses a number of special memory units called registers.

Secondary Storage

Secondary Storage image

Secondary Storage Image

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