NetBIOS is the most widely used networking API. The functions in this API are normally called by using Interrupt 5Ch. Current versions of Windows handle most NetBIOS functions. However, in order to maintain compatibility with future Windows products, the application should not make the NetBIOS call by using Interrupt 5Ch. Instead, it should set up all the registers for Interrupt 5Ch and then make a far call to the Windows NetBIOSCall function.
Windows does not support the following rarely used NetBIOS functions:
| Function number | Function name |
| 71h | Send.No.Ack |
| 72h | Chain.Send.No.Ack |
| 73h | Lan.Status.Alert |
| 78h | Find.Name |
| 79h | Trace |
For a full description of the NetBIOSCall function, see the Microsoft Windows Programmer's Reference, Volume 2.