Electronics Engineering (ELEX) Board Practice Exam

Which instruction is not considered a data copy or transfer instruction?

1. MOV

2. LOAD

3. DAS

4. STORE

The correct answer is: DAS

The instruction that is not considered a data copy or transfer instruction is DAS, which stands for Decimal Adjust after Subtraction. This instruction is specifically used to adjust the result of a subtraction operation to be a valid decimal representation. It is primarily utilized in BCD (Binary-Coded Decimal) arithmetic to correct any irregularities in the result of a subtraction involving decimal numbers. In contrast, MOV, LOAD, and STORE are all instructions that directly move data from one location to another. MOV is used to transfer data between registers, LOAD refers to transferring data from memory to a register, and STORE involves transferring data from a register back into memory. All of these facilitate the movement of data within the system, making them data copy or transfer instructions. Therefore, DAS stands out because its primary function is not about transferring data but rather adjusting arithmetic results.