Question

Explain flag regiter’s bit pattern by giving an example.

Answer 1

Suppose the flag register of the 8085 contains the value 45H, which in binary is 0100 0101.

The 8085 microprocessor has five status flags arranged as:

Flag register:	S	Z	-	Ac	-	P	-	Cy
Given: 45 H:	0	1	0	0	0	1	0	1

1. The sign flag is reset, which indicates that the result is positive (unsigned).
2. The zero flag is set, showing that the result of the arithmetic or logical operation is zero.
3. The auxiliary carry flag is reset, meaning no carry is produced from bit D₃ to D₄ during the operation.
4. The parity flag is set, which means the result stored in the accumulator has even parity (even number of 1s).
5. The carry flag is set, indicating that a carry or borrow occurs from the most significant bit during the arithmetic operation.