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DEC

Subtracts 1 from the value of the destination operand.

The following table covers what the source and destinations can be:

Support LOCK

The DEC instruction is available in both 64-bit mode and compatibility mode. When operating on a memory operand, the size of the operand is determined by the operand-size override prefix or the default size for the current mode (e.g., qword in 64-bit mode).

The DEC instruction does not affect the Carry Flag (CF). This differs from the SUB instruction, which does affect CF. Consequently, using DEC for loop counters or pointer arithmetic may lead to incorrect results if the program relies on the Carry Flag to detect underflow.