Computer memory types | RAM - ROM - SRAM

What are the main computer memory types? What types of memories exist in a standard computer? What is the role of each type of memory? Go ahead and read this article to get the answer for these and like questions.

Often the term “memory” confuses those with little knowledge about it. However, to put in simple terms, computer memory is a temporary workspace for a computer processor. A processor will put frequently used information on memory so that it will access quickly to carry out its task.

Major computer memory types

There are three major types of memory in a typical computer. All the other types of memories are grouped into one of the three.
These are:-

1. Read-Only Memory (ROM)

This type of memory holds information permanently written on it. Usually it is called non-volatile memory because it retains the information when the power is turned off. This is an important feature of Read Only Memory.

ROM is used to store computer startup instructions. The instruction is pre-programmed by the manufacturer; means you can’t modify or write back on ROM.

However, in recent systems it is possible to update BIOS using a new version supplied by the manufacturer.
The other types of non-volatile memory are EPROM and PROM.
PROM (Programmable read-only memory) is a type of ROM on which instruction is programmed. It used in video games to store instructions and settings.

EPROM (Erasable programmable read-only memory) is a type of ROM which can be erased and reprogrammable.

2. Random Access Memory (RAM)

This is a type of memory serves as main memory of a computer. It temporarily stores copy of information and files loaded from a computer hard drive that are required by a processor. After finishing the modification or change you made on the loaded file, it must be saved back to the hard drive before the power is turned off. If power is switched off without saving, you won’t retrieve the change made on the original file.

These computer memory types referred as volatile since they lose the information when the power is switched off.

Random Access Memory Types
There are many varieties of RAM, these are:-

  • Fast Page DRAM
  • Extended Data Out or EDO RAM is the other type of RAM which is faster than earlier memory types.
  • Synchronous DRAM (SDRAM) provides faster transfer speed between CPU and memory.
  • Double Data Rate SDRAM (DDRSDRAM) – its transfer speed is double that of SDRAM
  • DDR2 and DDR3 SDRAM – these are computer memory types found in recent systems. DDR3 is the latest and the fastest by breaking the maximum speed of 1066MHz achieved by DDR2 RAM. Its electric consumption is also lower than DDR2.

RAM is inexpensive and available at different capacity and size. However, comparing to the speed of a processor, computer memory is still slow, which hangs the performance a processor. To tackle this problem new type of memory is developed – SRAM.

3. Static RAM (SRAM)

Static RAM is different in its technology from other computer memory types. SRAM is special type of high-speed memory which serves to supply the most frequently used data instantly to a processor. Unlike main memory it can nearly run as fast as to the speed of a processor. This way a processor executes instructions more rapidly.

Static RAM referred as cache memory in modern systems. There are more than two levels (L1, L2, L3, etc) of cache exist in modern computer systems.

Level 1 is the fastest cache which is built directly on the CPU chip. In earlier systems, Level 2 cache is built on computer motherboard but connects with CPU using high-speed interface.

In recent systems L2 cache is also incorporated with a processor which boosts CPU performance significantly. The third type of cache is built outside the CPU.


Memory plays great role in computer systems. As we have discussed there are three computer memory types available in standard computer based on their function and physical makeup. However, only the main memory that can be upgraded and changed, the others comes with the system whether it is a processor, ROM or graphics card.

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