This document tries to explain the “why”, “what” and “how” details of input/output handling by Commodore 8-bit computers from the VIC-20 onwards. The specifics mentioned apply to the VIC-20, it is possible they vary slightly with other models.

In contrast to many other systems of the era Commodore designed a flexible and versatile interface to allow programmers to interact with peripherals and to enable new hardware devices to be integrated without major changes to applications.

BASIC programs can access printers, disk drives and other devices using high-level concepts with a set of simple commands. Machine code programs also have a well-defined and documented set of KERNAL routines which perform the equivalent functions