Looks like an Amiga Basic manual to me!
..but anyway.
AmigaBASIC was an interpreted BASIC programming language implementation for the Amiga, designed and written by Microsoft. AmigaBASIC shipped with AmigaOS versions 1.1 to 1.3. It succeeded Metacomco's ABasiC, which was included in AmigaOS 1.0 and 1.1, and it was replaced with ARexx, a REXX-style scripting language, from AmigaOS version 2.0 onwards