80386 Programmer's Reference Manual -- Opcode INC

INC -- Increment by 1

OpcodeInstructionClocks DescriptionExample
FE /0incb r/m8 Increment r/m byte by 1incb %dl
incb (%ebx,1)
incb m8(%ebx,1)
incb m8(%ebx,%ebp,1)
FF /0incw r/m16 Increment r/m word by 1incw %cx
incw (%ebx,1)
incw (%ebx,2)
incw (%ebx,%ebp,1)
FF /6incl r/m32 Increment r/m dword by 1incl %ecx
incl (%ebx,2)
incl (%ebx,4)
incl (%ebx,%ebp,1)
40 + rwincw r16 Increment word register by 1incw %bx
40 + rdincl r32 Increment dword register by 1incl %ebx


DEST := DEST + 1;


INC adds 1 to the operand. It does not change the carry flag. To affect the carry flag, use the ADD instruction with a second operand of 1.

Flags Affected

OF, SF, ZF, AF, and PF as described in Appendix C

Protected Mode Exceptions

#GP(0) if the operand is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault

Real Address Mode Exceptions

Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH

Virtual 8086 Mode Exceptions

Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault

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