2. WHAT IS INSTRUCTION ?
• A group of bits that tell the computer to perform a specific
• The instructions of a program are stored in memory.
• The CPU reads the next instruction from memory.
• It is placed in an Instruction Register (IR).
6. INSTRUCTION CYCLE
A instruction is executed in three phases :
– Fetch an instruction from memory
– Decode the instruction.
– Read the effective address from memory if the
instruction has an indirect address. (OPTIONAL)
– Execute the instruction.