FE /1         DEC r/m8                 Decrement r/m8 by 1

FF /1         DEC r/m16         Decrement r/m16 by 1

FF /1         DEC r/m32         Decrement r/m32 by 1

48+rw         DEC r16                 Decrement r16 by 1

48+rd         DEC r32                 Decrement r32 by 1


Description

Subtracts 1 from the destination operand, while preserving the state of the CF flag. The destination operand can be a register or a memory location. This instruction allows a loop counter to be updated without disturbing the CF flag. (To perform a decrement operation that updates the CF flag, use a SUB instruction with an immediate operand of 1.)


Operands        Bytes                Clocks

r8                   2                     1   UV

r16                  1                    1   UV

r32                  1                     1   UV

mem               2+d(0,2)        3   UV


Flags

The CF flag is not affected. The OF, SF, ZF, AF, and PF flags are set according to the result.

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