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I need to call a real mode interrupt (say int 21h), and I have to set DS:DX to the segment:offset of some data variable. How can I do that?

April 26, 2017DS DX int interrupt mode segment

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I need to call a real mode interrupt (say int 21h), and I have to set DS:DX to the segment:offset of some data variable. How can I do that?

1 Answer

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It’s possible to emulate the real mode interrupt by means of special DPMI function, which is implemented in MsDos and Intr procedures (see our on-line help system for the DOS unit description). Just keep in mind, that you have to allocate a data block in the low memory area (1st megabyte) using AllocDosMemoryBlock or DosMemoryAlloc function from the DPMI unit.