Int 21H Function Summary by Number

Hex Dec Function name Vers F/H (1)

00H 0 Terminate Process 1.0+

01H 1 Character Input with Echo 1.0+

02H 2 Character Output 1.0+

03H 3 Auxiliary Input 1.0+

04H 4 Auxiliary Output 1.0+

05H 5 Printer Output 1.0+

06H 6 Direct Console I/O 1.0+

07H 7 Unfiltered Character Input Without Echo 1.0+

08H 8 Character Input Without Echo 1.0+

09H 9 Display String 1.0+

0AH 10 Buffered Keyboard Input 1.0+

0BH 11 Check Input Status 1.0+

0CH 12 Flush Input Buffer and Then Input 1.0+

0DH 13 Disk Reset 1.0+

0EH 14 Select Disk 1.0+

0FH 15 Open File 1.0+ F

10H 16 Close File 1.0+ F

11H 17 Find First File 1.0+ F

12H 18 Find Next File 1.0+ F

13H 19 Delete File 1.0+ F

14H 20 Sequential Read 1.0+ F

15H 21 Sequential Write 1.0+ F

16H 22 Create File 1.0+ F

17H 23 Rename File 1.0+ F

18H 24 Reserved

19H 25 Get Current Disk 1.0+

1AH 26 Set DTA Address 1.0+

1BH 27 Get Default Drive Data 1.0+

1CH 28 Get Drive Data 2.0+

1DH 29 Reserved

1EH 30 Reserved

1FH 31 Reserved

20H 32 Reserved

21H 33 Random Read 1.0+ F

22H 34 Random Write 1.0+ F

23H 35 Get File Size 1.0+ F

24H 36 Set Relative Record Number 1.0+ F

25H 37 Set Interrupt Vector 1.0+

26H 38 Create New PSP 1.0+

27H 39 Random Block Read 1.0+ F

28H 40 Random Block Write 1.0+ F

29H 41 Parse Filename 1.0+

2AH 42 Get Date 1.0+

2BH 43 Set Date 1.0+

2CH 44 Get Time 1.0+

2DH 45 Set Time 1.0+

2EH 46 Set Verify Flag 1.0+

2FH 47 Get DTA Address 2.0+

30H 48 Get MS-DOS Version Number 2.0+

31H 49 Terminate and Stay Resident 2.0+

32H 50 Reserved

33H 51 Get or Set Break Flag, Get Boot Drive 2.0+

34H 52 Reserved

35H 53 Get Interrupt Vector 2.0+

36H 54 Get Drive Allocation Information 2.0+

37H 55 Reserved

38H 56 Get or Set Country Information 2.0+

39H 57 Create Directory 2.0+

3AH 58 Delete Directory 2.0+

3BH 59 Set Current Directory 2.0+

3CH 60 Create File 2.0+ H

3DH 61 Open File 2.0+ H

3EH 62 Close File 2.0+ H

3FH 63 Read File or Device 2.0+ H

40H 64 Write File or Device 2.0+ H

41H 65 Delete File 2.0+ H

42H 66 Set File Pointer 2.0+ H

43H 67 Get or Set File Attributes 2.0+

44H 68 IOCTL (I/O Control) 2.0+

45H 69 Duplicate Handle 2.0+

46H 70 Redirect Handle 2.0+

47H 71 Get Current Directory 2.0+

48H 72 Allocate Memory Block 2.0+

49H 73 Release Memory Block 2.0+

4AH 74 Resize Memory Block 2.0+

4BH 75 Execute Program (EXEC) 2.0+

4CH 76 Terminate Process with Return Code 2.0+

4DH 77 Get Return Code 2.0+

4EH 78 Find First File 2.0+ H

4FH 79 Find Next File 2.0+ H

50H 80 Reserved

51H 81 Reserved

52H 82 Reserved

53H 83 Reserved

54H 84 Get Verify Flag 2.0+

55H 85 Reserved

56H 86 Rename File 2.0+

57H 87 Get or Set File Date and Time 2.0+ H

58H 88 Get or Set Allocation Strategy 3.0+

59H 89 Get Extended Error Information 3.0+

5AH 90 Create Temporary File 3.0+ H

5BH 91 Create New File 3.0+ H

5CH 92 Lock or Unlock File Region 3.0+ H

5DH 93 Reserved

5EH 94 Get Machine Name, Get or Set Printer 3.1+

Setup

5FH 95 Device Redirection 3.1+

60H 96 Reserved

61H 97 Reserved

62H 98 Get PSP Address 3.0+

63H 99 Get DBCS Lead Byte Table 2.25

only

64H 100 Reserved

65H 101 Get Extended Country Information 3.3+

66H 102 Get or Set Code Page 3.3+

67H 103 Set Handle Count 3.3+

68H 104 Commit File 3.3+ H

69H 105 Reserved

6AH 106 Reserved

6BH 107 Reserved

6CH 108 Extended Open File 4.0+ H

(1) Specifies whether file functions are FCB- or handle-related.