Introduction

Dyalog includes a collection of built-in facilities that provide various services related to both the APL and the external environment. They have distinguished case-insensitive names beginning with the ⎕ symbol, and are implicitly available in a clear workspace. Collectively, these facilities are referred to as System Functions but they are variously implemented as constants, variables, functions, operators, and in one case, as a namespace.

Note that Dyalog can extend any of these facilities by, for example, adding extra elements, rows, or columns to a result, so code should take this possibility into account.