How Do You Know If Zero Flag Is Set?

For example, if the result of an arithmetic operation is zero , the zero flag is set (i.e., ZF = 1). Once a flag is set or cleared, it remains in that state until another instruction changes its value. Note that not all assembly language instructions affect all the flags.

How do you know if a flag is set?

The flag should never touch anything beneath it , such as the ground, the floor, water, or merchandise. The flag should never be carried flat or horizontally, but always aloft and free. The flag should never be fastened, displayed, used, or stored so that it might be easily torn, soiled, or damaged in any way.

Which flag is set when the result is zero?

Along with a carry flag, a sign flag and an overflow flag, the zero flag is used to check the result of an arithmetic operation, including bitwise logical instructions. It is set to 1, or true, if an arithmetic result is zero, and reset otherwise.

How do you find a zero flag?

The Zero flag indicates that an operation produced zero . For example, if an operand is subtracted from another of equal value, the Zero flag is set. The Sign flag indicates that an operation produced a negative result. If the most significant bit of the destination operand is set, the Sign flag is set.

What are the conditions to set or reset the flags?

Here’s a chart that compares the flag states to test operands. The argument is subtracted from a without modifying a , i.e. a – arg1 . If arg1 is greater than a then a carryover event happens and the carry flag is set. If arg1 is less than a , then no event occurred so the carry flag is reset .

Which instruction does not affect any flag?

As there is no arithmetic or logical operation being performed, no flags are affected by data transfer instructions . Arithmetic instruction: Arithmetic Instructions are the instructions that perform basic arithmetic operations such as addition, subtraction, and a few more.

What is difference between carry and auxiliary carry flag?

The auxiliary carry flag AF watches for a 4-bit (nibble) carry , while the common carry flag CF watches for a carry-out from the MSB of the operand size.

Which is the only one instruction uses the auxiliary carry flag?

Auxiliary Carry Flag (AF) is one of the six status flags in the 8086 microprocessor. This flag is used in BCD (Binary-coded Decimal) operations . The status of this flag is updated for every arithmetic or logical operation performed by ALU.

How many flags does 8086 have?

There are total 9 flags in 8086 and the flag register is divided into two types: (a) Status Flags – There are 6 flag registers in 8086 microprocessor which become set(1) or reset(0) depending upon condition after either 8-bit or 16-bit operation. These flags are conditional/status flags.

Which are different flags in PSW register?

Which flag is not considered for conditional branching?

There is another flag bit at bit[27], called the Q flag . It is for saturation math operations and is not used for conditional branches.

What is Cpsr arm?

ARM v6/v7 maintains a status register called the CPSR ( current program status register ) that holds four status bits, negative (N), zero (Z), carry (C), and overflow (O). These bits can be used for conditional execution of subsequent instructions.

Which flag is affected by MOV instruction?

The MOV instruction never affects the flags . Whenever the destination operand equals Zero, the Zero flag is set. A flag is set when it equals 1. A flag is clear when it equals 0.

Why flag is called PSW?

The Program Status Word (PSW) contains status bits that reflect the current CPU state . The 8051 variants provide one special function register called PSW with this status information. The 251 provides two additional status flags, Z and N, that are available in a second special function register called PSW1.

Which flag is used to debug program?