The standard character input/output (I/O) functions handle all input to and output from character devices, such as consoles, printers, and serial ports.
Following are the MS-DOS character I/O functions:
| Function | Description | Version |
| 01h | Read Keyboard with Echo | 1.0 |
| 02h | Display Character | 1.0 |
| 03h | Auxiliary Input | 1.0 |
| 04h | Auxiliary Output | 1.0 |
| 05h | Print Character | 1.0 |
| 06h | Direct Console I/O | 1.0 |
| 07h | Direct Console Input | 1.0 |
| 08h | Read Keyboard Without Echo | 1.0 |
| 09h | Display String | 1.0 |
| 0Ah | Buffered Keyboard Input | 1.0 |
| 0Bh | Check Keyboard Status | 1.0 |
| 0Ch | Flush Buffer, Read Keyboard | 1.0 |