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C-3
INSTRUCTION SET DESCRIPTIONS
Table C-3. Flag Bit Functions
Name Function
AF Auxiliary Flag:
Set on carry from or borrow to the low order four bits of AL; cleared otherwise.
CF Carry Flag:
Set on high-order bit carry or borrow; cleared otherwise.
DF Direction Flag:
Causes string instructions to auto decrement the appropriate index register
when set. Clearing DF causes auto increment.
IF Interrupt-enable Flag:
When set, maskable interrupts will cause the CPU to transfer control to an
interrupt vector specified location.
OF Overflow Flag:
Set if the signed result cannot be expressed within the number of bits in the
destination operand; cleared otherwise.
PF Parity Flag:
Set if low-order 8 bits of result contain an even number of 1 bits; cleared
otherwise.
SF Sign Flag:
Set equal to high-order bit of result (0 if positive, 1 if negative).
TF Single Step Flag:
Once set, a single step interrupt occurs after the next instruction executes. TF
is cleared by the single step interrupt.
ZF Zero Flag:
Set if result is zero; cleared otherwise.