## ALP Programming Guide and Reference

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### Description

The INS instruction transfers data from the input port numbered by the DX register to the memory byte or word at ES:dest-index. The memory operand must be addressable from the ES register; no segment override is possible. The destination register is the DI register if the address-size attribute of the instruction is 16-bits, or the EDI register if the address-size attribute is 32-bits.

The INS instruction does not allow the specification of the port number as an immediate value. The port must be addressed through the DX register value. Load the correct value into the DX register before running the INS instruction.

The destination address is determined by the contents of the destination index register. Load the correct index into the destination index register before running the INS instruction.

After the transfer is made, the DI or EDI register advances automatically. If the DF flag is 0 (a CLD instruction was run), the DI or EDI register increments; if the DF flag is 1 (an STD instruction was run), the DI or EDI register decrements. The DI register increments or decrements by 1 if a byte is input, by 2 if a word is input, or by 4 if a doubleword is input.

The INSB, INSW and INSD instructions are synonyms of the byte, word, and doubleword INS instructions. The INS instruction can be preceded by the REP prefix for block input of CX bytes or words. Refer to the REP instruction for details of this operation.