6. COMPUTER STORAGE DEVICES

  The equipment that the computer uses for storing data and information is referred to as STORAGE DEVICES or MEMORY. Computer can keep information in its memory for future use. Computer is the computer store.

•There are two main types of memory, the main memory and the auxiliary

memory.

The main memory:  

This is the internal memory and it is an extension of the central processing unit. The main memory is directly accessible by the CPU and it is regarded as the computer’s primary storage or memory.

Uses of main memory    

All data requiring processing must be brought to the main memory.  The main memory stores:

  i.   Instructions the CPU is waiting to obey

  ii.  Instructions the CPU is currently obeying

  iii. Data waiting for processing is usually stored in an area of the        main memory called Buffer. 

The Auxiliary Memory:

•  The auxiliary storage or memory is the secondary storage device.  It is also called external storage device because it is external to the CPU.

• It is a mass storage unit since it stores a large amount of information.  The auxiliary memory is used to supplement or assist the main memory.

•During processing, the CPU fetches or collects necessary data or information from the auxiliary memory to the main memory before processing.  This is why processing from the auxiliary memory takes more time than form the main memory.

•Data is usually transferred in large quantity from the auxiliary memory to the main memory at one time.  Data is usually copied, hence there is no loss of data from the auxiliary memory during transfer.

• The data transferred or copied is temporarily stored in the main memory.  The data transferred to the main memory at one time must not exceed the size of the main memory.

 

Comparisons between Main Memory and Auxiliary Memory

 Main Memory                                Auxiliary  Memory         

 

1.Primary storage                                        Secondary Storage

2.Internal                                                     External

3.Faster                                                        Slower

4.Expensive                                                  Inexpensive

5.Small Capacity                                          Bigger-capacity storage     

6.The RAM, which is the greater part,        Does not loose information when the              

   can loose information once the power       power supply is off.                          

   supply is off.