Computer Memory & Its Types - Banking Notes

Computer Memory & Its Types

Introduction of Computer Memory:

• The computer memory is the physical device which is capable to store the information permanently or temporarily. It is one of the most essential part of computer. The memory helps to store both of the data and the instruction which would be executed. The CPU (Central Processing Unit) accesses each location in the memory by using the unique memory address.

Types of Computer Memory:

• The total memory capacity of a computer can be divided into four types i.e. Secondary Memory, Main Memory or Primary Memory, Cache Memory and Internal Memory.

Secondary Memory:

• This type of memory is used to store the data and information as this is used in bulk size.
• Programs which are not currently needed are transferred to the secondary memory from the main memory to provide the spaces for currently needed program.
• It provides back-up storage.
• It is a low cost and slow speed device.
• Example- Magnetic Disc, Floppy Disc.

Primary Memory / Main Memory –

• This type of memory communicates directly with the CPU.
• The data and programs, which are currently needed by the CPU for the execution, reside in the main memory. 
• It occupies the central position in the hierarchy of the memory as it is capable to communicate directly with the CPU and the secondary memory devices.
• It comprises of two buses – Address BUS and Memory BUS.
• Main Memory is of two types- RAM (Random Access Memory) and ROM (Read Only Memory).

RAM-

• It is a Read-Write memory which can perform both of the reading and writing tasks.
• It is a volatile memory (if power is switched off, all information must be lost).
• It is of two types i.e. Static RAM (SRAM) and Dynamic RAM (Dynamic RAM).

SRAM-

• It is small in capacity and requires constant power supply.
• Its speed is high and is faster as it has lower access time.
• It contains 6 transistors.

DRAM-

• It is large in capacity and requires reduced power consumption.
• Its speed is less and cost is low.
• It contains one transistor and one capacitor.
• DRAM is of 5 types i.e. Synchronous DRAM, Asynchronous DRAM, DDRSDRAM (Double Data Rate Synchronous DRAM), Rambus DRAM and Cache DRAM.

ROM-

• This type of memory is used only for read operation.
• It is a non-volatile memory.
• It is of 4 types i.e. Programmable ROM (PROM), Erasable Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM) and Flash Memory. 
• PROM- The user can load the data once and after that it can’t be changed.
• EPROM- This kind of ROM uses a transistor as a programmable switch. In this memory, data can be erased by using ultra violet rays.
• EEPROM- Data can be erased electrically. It can perform both of the read and write operation.
• Flash Memory- It is a special kind of EEPROM in which data can be read and erased in large blocks.

Cache Memory – 

• It is the small sized, high speed volatile main memory which is much faster than regular RAM.
• It makes data and programs available at a rapid rate and therefore increases the performance of computer.

Internal Memory-

• It refers to a high speed register used inside the CPU.
• It holds temporary results inside the CPU when the computation is in progress.