String processing instructions
The classification of string processing instructions is as follows:
| Directive Type | ||
|---|---|---|
| MOVS | move string | Transmission |
| CMPS | compare string | String comparison |
| SCAS | scan string | String scan |
| LODS | load from string | Get from the string |
| STOS | store in to string | Save string |
| INS | input from port to string | String input |
| OUTS | output string to port | String output |
| REP | repeat | repeat |
| REPE/REPZ | repeat while equal/zero | If equal/zero, repeat |
| REPNE/REPNZ | repeat while not equal/zero | If not equal / if not zero, repeat |
Format:
MOVS DST,SRC
MOVSB (bytes)
MOVSW (word)
MOVSD (Double Word) (386 and its successor models are available)
usage:
The instruction can pass a byte, word or double word (DS:SI) in the data segment pointed to by SI to a byte, word or double word (ES:DI) in the additional segment pointed to by DI, without affecting the conditional flag bits, and modify the SI and DI according to the DF and data format.
Format:
CMPS SRC,DST
CMPSB (bytes)
CMPSW (word)
CMPSD (double-word) (386 and its successor models are available)
usage:
The instruction subtracts the data in the memory unit pointed to by DS:SI with the data in the memory unit pointed to by ES:SI, does not save the result but affects the condition flag bits, and modifies SI and DI according to the value of DF.
Format:
SCAS DST
SCASB (bytes)
SCASW (word)
SCASD (double word) (386 and its successor models are available)
usage:
The instruction subtracts the data in AL, AX or EAX from the data in the memory unit pointed to by ES:DI, does not save the result but affects the condition flag bits, and modifies SI and DI according to the value of DF.
Format:
LODS SRC
LODSB (bytes)
LODSW (word)
LODSD (double-word) (386 and its successor models are available)
usage:
The instruction sends the data in the memory unit pointed to by DS:SI to AL, AX, or EAX, and modifies the SI according to the value and data type of the condition flag bit DF.
Format:
STOS DST
STOSB (bytes)
STOSW (word)
STOSD (Double Word) (386 and its successor models are available)
usage:
The instruction stores the contents in AL, AX and EAX into the storage unit pointed to by DS:SI, and modifys the SI according to the value and data type of DF.
Format:
INS DST,DX
INSB (bytes)
INSW (word)
INSD (Double Word) (386 and its successor models are available)
usage:
The instruction sends the data of the I/O space ported in the DX register to the memory unit pointed to by ES:DI, and modifies the DI according to the value and data type of DF.
Format:
OUTS DX,SRC
OUTSB (bytes)
OUTSW (word)
OUTSD (Double Word) (386 and its successor models are available)
usage:
The instruction sends the data in the memory unit pointed to by DS:SI to the I/O port in the DX register, and changes the SI according to the value and data type of DF.
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