Primary Memory :
It is also known as Main Memory. It us the internal storage memory used by computer to hold data and instructions. The primary memory has limited storage capacity.
Primary memory holds the data and programs needed at that instant by CPU.
Primary memory is volatile in nature i.e. it requires constant power supply to motion the current information.
There are two types of Primary Memory:
If current is interrupted, data is lost. It is an integrated circuit that enables you to access the stored data in random order constantly.
It is also known as Main Memory. It us the internal storage memory used by computer to hold data and instructions. The primary memory has limited storage capacity.
Primary memory holds the data and programs needed at that instant by CPU.
Primary memory is volatile in nature i.e. it requires constant power supply to motion the current information.
There are two types of Primary Memory:
- RAM
- ROM
(i) RAM
RAM stands for Random Access Memory. It is the internal memory that can be read from as well as written to. This memory is often associated with volatile types of memory. It can hold data only on temporary basis because it requires continuous flow of electrical current.
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| Fig. Primary Memory |
The Two main forms of RAM are:
(a) Static RAM : It is also written as SRAM. It is a computer memory that requires a constant power flow in order to hold information. SRAM is more expensive and requires more power therefore it is commonly used in cache and video card memory. It is faster than DRAM.
(b) Dynamic Ram : It is also written as DRAM. It stores information in a cell containing a capacitor and transistor, these cells must be refreshed with electric impulses in few milliseconds. This process allows memory to keeping charge and hold the data as long as needed.
These are some enhanced versions of RAM which are as follows:
(a) EDORAM (Extended Data Output Random Access Memory)
(b) SDRAM (Synchronous Dynamic Random Access Memory)
(c) DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory)
(ii) ROM
In ROM (Read Only Memory) information once stored remain fixed, i.e. it can not be changed. So, ROM can be changed. So, ROM can only be read and used.
Generally, it contains a set of start-up instructions, i.e. what to do when a computer is turned ON. The content of ROM remain stored even if power is turned OFF. This memory is often associated with non-volatile types of memory. A ROM cannot be altered once the chip has been made.
ROM is further sub divided into several types:
(a) PROM (Programmable Read Only Memory) It is a computer memory chip capable to being programmed after it has been created. But once the PROM has been programmed, the information written is permanent and cannot be erased or deleted.
(b) EPROM (Erasable Programmable Read Only Memory) It is a computer memory chip on which the written information can be changed by exposing to ultra violet light. It is just like a small glass circle that expose the chip that can be re-programmed.
(c) EEPROM (Electrically Erasable Programmable Read Only Memory) It is a PROM that can be erased and re-programmed using as electrical charge.