Lods-stos-string manipulating instruction-microprocessor, Assembly Language

LODS : Load String Byte or String Word:-

The LODS instruction loads AL/AX register by the content of a string pointed to by DS:SI register pair. The SI is automatically modified depending on the DF. If it is a byte transfer (LODSB), SI is modified by one and if it is a word transfer (LODSW), the SI is modified by two. No other flags are changed by this instruction.

STOS : Store String Byte or String Word:-

The STOS instruction stores the AL/AX register contents to a location in the string pointed by theES: Dl register pair. Accordingly the Dl is modified. No flags are changed by this instruction. The direction flag controls the string instruction execution. The source index (SI) and destination index (D1) are automatically modified after each iteration. If the DF = 1, then the execution follows auto decrement mode. In this mode, DI and Sl are decremented automatically after each iteration (by 1 or 2 depending on the word or byte operations). Hence, in auto decrementing mode, the strings are mention to by their ending addresses. If the DF = 0, then the execution follows autoincrement mode. In this mode, D1 and S1 are incremented automatically (by 1 or 2 depending on word or byte operation) after each iteration, so in this case, the strings are mention to by their starting addresses.

Posted Date: 10/12/2012 3:41:19 AM | Location : United States







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