After the personal computer is popular, MS-DOS is widely used. Because of its ease of use, it varies. Like MS-DOS, the reference book for DOS programming is omnipure. They have a long appendix after they have explained the invocation of INT21. Look carefully that you will find that the int21 function number jumps directly from 4CH to 54h and only the word does not mention those function numbers between them, and only "reserve". However, this is just a horn of the iceberg. Another hidden part of DOS is 5DH used, which contains 12 subtasks that handle various functions. Also, even the calls described in INT 21, there are also many sub-features that are not used ... DOS until now is not a closed, static world. This article tried to make a reasonable explanation on their existence, and if there is an improper story, please forgive. Agreement: 1 This article span from DOS 1.0 ~ 6.0 2 terms: Asciz End ASCII string BPD BIOS parameter block (INT 21H / AH = 53H) CDS current directory structure (INT 21H / AJ = 52H) DPB DOS drive Parameter (INT21H / AH = 32H) DPL DOD Parameter Table (INT 21H / AX = 5D00H) DTA Disk Transfer Address FAT File Allocation Table FCB File Control Block SFT System File SDA DOS An Elimination Data Area PSP Block Prefix (Unfinished Continue ... ^ __ ^ Thank you for your attention)
