# machine instructions

+2 votes

Assume that EA = (X)+ is the effective address equal to the contents of location X, with X incremented by one word length after the effective address is calculated; EA = −(X) is the effective address equal to the contents of location X, with X decremented by one word length before the effective address is calculated; EA = (X)− is the effective address equal to the contents of location X, with X decremented by one word length after the effective address is calculated. The format of the instruction is (opcode, source, destination), which means (destination ← source op destination). Using X as a stack pointer, which of the following instructions can pop the top two elements from the stack, perform the addition operation and push the result back to the stack.

1. ADD (X)−, (X)
2. ADD (X), (X)−
3. ADD −(X), (X)+
4. ADD −(X), (X)

sir pls make me understand the question. i am not able to interpret the ques. it seems quite confusing...

asked Jan 3

## 1 Answer

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answered Jan 4 by (23,090 points)