qa.hlp (Table of Contents; Topic list)
Important Notice
The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.
Interrupt 21H Summary (DOS)
   INT 21H Summary  Contents  Index  INT Instruction
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Category                  Description
Character I/O             Old-style (DOS1) read and write to devices
Directory Operations      Get, set, create, and delete directory
Disk Management           Select drive and get drive status
File Operations           Open, close, and manage files
File Operations (FCB)     Functions use File Control Block--not recommended
Memory Management         Allocate or resize memory block
Miscellaneous             Miscellaneous system functions
Process Management        Execute or terminate process
Record Operations         Read and write to file
Record Operations (FCB)   Functions use File Control Block--not recommended
Time and Date             Get or set date and time
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