Monday 22 October 2012

FLAG REGISTER OF 8086

Flags is a 16-bit register containing 9 1-bit flags:
  • Overflow Flag (OF) - set if the result is too large positive number, or is too small negative number to fit into destination operand.
  • Direction Flag (DF) - if set then string manipulation instructions will auto-decrement index registers. If cleared then the index registers will be auto-incremented.
  • Interrupt-enable Flag (IF) - setting this bit enables maskable interrupts.
  • Single-step Flag (TF) - if set then single-step interrupt will occur after the next instruction.
  • Sign Flag (SF) - set if the most significant bit of the result is set.
  • Zero Flag (ZF) - set if the result is zero.
  • Auxiliary carry Flag (AF) - set if there was a carry from or borrow to bits 0-3 in the AL register.
  • Parity Flag (PF) - set if parity (the number of "1" bits) in the low-order byte of the result is even.
  • Carry Flag (CF) - set if there was a carry from or borrow to the most significant bit during last result calculation.

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