Understanding PUSH Instruction
The instruction "PUSH" is commonly used in assembly language programming, particularly in microprocessor architecture. It is essential to comprehend the addressing modes utilized by such instructions.
Addressing Modes Overview
Addressing modes define how the operand of an instruction is accessed. In the context of the PUSH instruction, the options provided were:
- a) Immediate
- b) Register
- c) Direct
- d) Register Indirect
Why Register Indirect is Correct
The correct answer is option 'd' - Register Indirect. Here’s why:
- Definition of Register Indirect: In this mode, the address of the operand is found in a register. The instruction uses the content of the register as a pointer to access the data.
- PUSH Operation: The PUSH instruction typically involves transferring data from a register (or memory) onto the stack. When using Register Indirect, a register holds the address of the data that needs to be pushed.
- Example: If a register (say R1) contains the address of the data, the PUSH instruction will access the data at that address and place it on the stack.
Other Addressing Modes Explained
- Immediate: The operand is specified explicitly within the instruction itself (e.g., PUSH 5).
- Register: The operand is taken directly from a register (e.g., PUSH R1).
- Direct: The operand’s address is specified directly in the instruction.
In summary, while other addressing modes have their uses, the Register Indirect mode is specifically suited for the PUSH operation, as it allows dynamic access to memory locations using the address stored in a register.