Int 21H Function Summary by Category

Hex Dec Function name Vers F/H

Character I/O

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+

File Operations

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

16H 22 Create File 1.0+ F

17H 23 Rename File 1.0+ F

23H 35 Get File Size 1.0+ F

29H 41 Parse Filename 1.0+ F

3CH 60 Create File 2.0+ H

3DH 61 Open File 2.0+ H

3EH 62 Close File 2.0+ H

41H 65 Delete File 2.0+ H

43H 67 Get or Set File Attributes 2.0+

45H 69 Duplicate Handle 2.0+

46H 70 Redirect Handle 2.0+

4EH 78 Find First File 2.0+ H

4FH 79 Find Next File 2.0+ H

56H 86 Rename File 2.0+

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

5AH 90 Create Temporary File 3.0+ H

5BH 91 Create New File 3.0+ H

67H 103 Set Handle Count 3.3+

68H 104 Commit File 3.3+ H

6CH 108 Extended Open File 4.0+ H

Record Operations

14H 20 Sequential Read 1.0+ F

15H 21 Sequential Write 1.0+ F

1AH 26 Set DTA Address 1.0+

21H 33 Random Read 1.0+ F

22H 34 Random Write 1.0+ F

24H 36 Set Relative Record Number 1.0+ F

27H 39 Random Block Read 1.0+ F

28H 40 Random Block Write 1.0+ F

2FH 47 Get DTA Address 2.0+

3FH 63 Read File or Device 2.0+ H

40H 64 Write File or Device 2.0+ H

42H 66 Set File Pointer 2.0+ H

5CH 92 Lock or Unlock File Region 3.0+ H

Directory Operations

39H 57 Create Directory 2.0+

3AH 58 Delete Directory 2.0+

3BH 59 Set Current Directory 2.0+

47H 71 Get Current Directory 2.0+

Disk Management

0DH 13 Disk Reset 1.0+

0EH 14 Select Disk 1.0+

19H 25 Get Current Disk 1.0+

1BH 27 Get Default Drive Data 1.0+

1CH 28 Get Drive Data 2.0+

2EH 46 Set Verify Flag 1.0+

36H 54 Get Drive Allocation Information 2.0+

54H 84 Get Verify Flag 2.0+

Process Management

00H 0 Terminate Process 1.0+

26H 38 Create New PSP 1.0+

31H 49 Terminate and Stay Resident 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+

62H 98 Get PSP Address 3.0+

Memory Management

48H 72 Allocate Memory Block 2.0+

49H 73 Release Memory Block 2.0+

4AH 74 Resize Memory Block 2.0+

58H 88 Get or Set Allocation Strategy 3.0+

Network Functions

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

Setup

5FH 95 Device Redirection 3.1+

Time and Date

2AH 42 Get Date 1.0+

2BH 43 Set Date 1.0+

2CH 44 Get Time 1.0+

2DH 45 Set Time 1.0+

Miscellaneous System Functions

25H 37 Set Interrupt Vector 1.0+

30H 48 Get MS-DOS Version Number 2.0+

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

35H 53 Get Interrupt Vector 2.0+

38H 56 Get or Set Country Information 2.0+

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

59H 89 Get Extended Error Information 3.0+

63H 99 Get Lead Byte Table 2.25

only

65H 101 Get Extended Country Information 3.3+

66H 102 Get or Set Code Page 3.3+

Reserved Functions

18H 24 Reserved

1DH 29 Reserved

1EH 30 Reserved

1FH 31 Reserved

20H 32 Reserved

32H 50 Reserved

34H 52 Reserved

37H 55 Reserved

50H 80 Reserved

51H 81 Reserved

52H 82 Reserved

53H 83 Reserved

55H 85 Reserved

5DH 93 Reserved

60H 96 Reserved

61H 97 Reserved

64H 100 Reserved

69H 105 Reserved

6AH 106 Reserved

6BH 107 Reserved