# STD
# Set Direction Flag
| Opcode | Mnemonic | Description |
|---|---|---|
| FD | STD | Set DF flag. |
# Description
Sets the DF flag in the EFLAGS register. When the DF flag is set to 1, string operations decrement the index registers (ESI and/or EDI).
# Operation
DF = 1;
1
2
2
# Flags affected
The DF flag is set. The CF, OF, ZF, SF, AF, and PF flags are unaffected.