Question

How do you implement boolean return values (true/false) from commands like x < y, x > y, etc. in assembler?

Answer 1

In assembly language, boolean return values from comparisons are implemented using conditional jump instructions following a CMP instruction. The result of the comparison sets specific flags which are then used to determine the flow of the program and to set a register to 1 (true) or 0 (false) accordingly.

Step-by-step explanation:

To implement boolean return values such as true or false from comparison commands in assembler, one can utilize the conditional jump instructions provided by most assembly languages. These instructions are used after a comparison instruction, like CMP, to determine the flow of execution based on the flags set by the comparison.

Here is an example using x86 assembly language:

• Assuming x and y are variables, you compare them using the CMP instruction.
• Based on the comparison you want to make (x < y, x > y, etc.), you use a corresponding conditional jump such as JL (jump if less) or JG (jump if greater) instruction.
• The jump instruction will redirect the flow to different parts of the code depending on the outcome of the comparison.
• To return a boolean value, you might set a specific register to 1 (true) or 0 (false) based on the result of the jump.

Here is a simple snippet:

1. CMP x, y ; Compare x and y.
2. JL .isLessThan ; If x is less than y, jump to .isLessThan.
3. MOV result, 0 ; Set result to false.
4. JMP .done ; Skip the next line and jump to .done.
5. .isLessThan:
6. MOV result, 1 ; Set result to true.
7. .done:

In this example, if x is less than y, the result will be set to true. Otherwise, it will remain false.