مدرس المادة

MEMORY: 
It is a storage device. It stores program instructions, data and the results. 
There are two kind of memories; 
semiconductor memories & magnetic memories. (1): Semiconductor 
memories are faster, smaller, and lighter and consume less power. 
Semiconductor memories are used as the main memory of a computer. (2): 
Magnetic memories are slow but they are cheaper than semiconductor 
memories. Magnetic memories are used as the secondary memories of a 
computer for bulk storage of data and information’s. 
If a memory stores N- words of information each word being of m bits, we say 
it is a N x m memory. E.g. 8x4 memory means there are 8 words and each word 
containing 4- bit of information (called nibble). 8 words are stored at 8-memory 
locations and these memory locations are clearly identified by 8 unique 
addresses. 

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