1. The instruction that loads the AH register with the lower byte of the flag register is
a) SAHF
b) AH
c) LAHF
d) PUSHF
Explanation: The instruction LAHF(Load AH from a lower byte of Flag) may be used to observe the status of all the condition code flags(except overflow flag) at a time.
2. The instruction that pushes the flag register on to the stack is
a) PUSH
b) POP
c) PUSHF
d) POPF
Explanation: The instruction PUSHF(push flags to stack) pushes the flag register on to the stack.
3. The instruction that loads the flag register completely from the word contents of the memory location is
a) PUSH
b) POP
c) PUSHF
d) POPF
Explanation: POPF is pop flags to stack.
4. The instruction that adds immediate data/contents of the memory location specified in an instruction/register to the contents of another register/memory location is
a) SUB
b) ADD
c) MUL
d) DIV
Explanation: ADD instruction adds the data.
5. The instruction that supports addition when carry exists is
a) ADD
b) ADC
c) ADD & ADC
d) None of the mentioned
Explanation: ADC(Add with Carry) instruction performs the same operation as ADD operation, but adds the carry flag bit to the result.
6. The mnemonic that is placed before the arithmetic operation is performed is
a) AAA
b) AAS
c) AAM
d) AAD
Explanation: The AAD instruction converts two unpacked BCD digits in AH and AL to the equivalent binary number in AL.
7. The Carry flag is undefined after performing the operation
a) AAA
b) ADC
c) AAM
d) AAD
Explanation: Since the operation, AAD is performed before division operation is performed, the carry flag, auxiliary flag and overflow flag are undefined.
8. The instruction that performs logical AND operation and the result of the operation is not available is
a) AAA
b) AND
c) TEST
d) XOR
Explanation: In the TEST instruction, the logical AND operation is performed and the result is not stored but flags are affected.
9. In the RCL instruction, the contents of the destination operand undergo function as
a) carry flag is pushed into LSB & MSB is pushed into the carry flag
b) carry flag is pushed into MSB & LSB is pushed into the carry flag
c) auxiliary flag is pushed into LSB & MSB is pushed into the carry flag
d) parity flag is pushed into MSB & LSB is pushed into the carry flag
Explanation: In RCL(Rotate right through carry), for each operation, the carry flag is pushed into LSB and the MSB of the operand is pushed into carry flag.
10. The instruction that is used as prefix to an instruction to execute it repeatedly until the CX register becomes zero is
a) SCAS
b) REP
c) CMPS
d) STOS
Explanation: The instruction to which the REP is prefix, is executed repeatedly until CX register becomes zero. When CX becomes zero, the execution proceeds to the next instruction in sequence.