# Register - Status Flag

The `status flags` (bits 0, 2, 4, 6, 7, and 11) of the EFLAGS register indicate the results of arithmetic instructions.

## 3 - Usage

### 3.1 - One instruction, multiple Data Type Result

The `status flags` allow a single arithmetic instructions to produce results for three different data types:

If the result of an arithmetic operation is treated as:

• an unsigned integer, the CF flag indicates an out-of-range condition (carry or a borrow);
• a signed integer (two’s complement number), the OF flag indicates a carry or borrow;
• a BCD digit, the AF flag indicates a carry or borrow.

where:

### 3.2 - Multiple-precision arithmetic on integers

When performing multiple-precision arithmetic on integers, the CF flag is used in conjunction with the add with carry (ADC) and subtract with borrow (SBB) instructions to propagate a carry or borrow from one computation to the next.

### 3.3 - Conditional value

The condition instructions use one or more of the status flags as condition codes and test them for:

• setbyte,
• or end-loop conditions

## 4 - Management

### 4.1 - List

The status flag functions are:

Code Bit Name Description
`CF` 0 Carry flag Set if an arithmetic operation generates:
* a carry
* or a borrow
out of the most significant bit of the result;
cleared otherwise.
This flag indicates an overflow condition for unsigned-integer arithmetic. It is also used in multiple-precision arithmetic.
`PF` 2 Parity flag Set if the least-significant byte of the result contains an even number of 1 bits; cleared otherwise
`AF` 4 Auxiliary Carry flag Set if an arithmetic operation generates:
* a carry
* or a borrow out of bit 3 of the result;
cleared otherwise.
This flag is used in binary-coded decimal (BCD) arithmetic.
`ZF` 6 Zero flag Set if the result is zero; cleared otherwise.
`SF` 7 Sign flag Set equal to the most-significant bit of the result, which is the sign bit of a signed integer. (0 indicates a positive value and 1 indicates a negative value.)
`OF` 11 overflow flag Set if the integer result is:
* too large a positive number
* or too small a negative number (excluding the sign-bit)
to fit in the destination operand; cleared otherwise.
This flag indicates an overflow condition for signed-integer (two’s complement) arithmetic.