What is INT 21h?

operating-system interrupt low-level internals
Stefano Borini picture Stefano Borini · Aug 7, 2009 · Viewed 27.4k times · Source

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I wondered about the INT 21h as a concept. Now, I have some very rusty knowledge of the internals, but not so many details. I remember that in C64 you had regular Interrupts and Non Maskable Interrupts, but my knowledge stops here. Could you please give me some clue ? Is it a DOS related strategy ?

Answer

Otávio Décio picture Otávio Décio · Aug 7, 2009

From here: A multipurpose DOS interrupt used for various functions including reading the keyboard and writing to the console and printer. It was also used to read and write disks using the earlier File Control Block (FCB) method.

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