Q. What is Instruction Register?

Instruction Register (IR): Here instructions are loaded before execution. Comments on figure above are as below:

• All representations are in decimals. (In real machines the representations are in Binary).
• Number of Memory Locations = 16
• Size of every memory location = 16 bits = 2 Bytes (Compare with contemporary machines word size of 16, 32, 64 bits)
• So size of this sample memory = 16 words (Compare it with actual memory) size that is 128 MB, 256 MB, 512 MB, or more).
• In the diagram MAR is pointing to location 10.
• Last operation carried out was 'read memory location 10' that is 65 in this. So the Contents of MBR is also 65.