one, many Microsoft BASIC variants allowed only two) procedures with local variables (indeed, all variables in BASIC09 are local to procedures) and parameter passing by reference a reasonable debugger (its only significant drawback was that one could not examine the contents of fields in structures) a way to interface to machine language code, which could be passed parameters using the BASIC09 calling sequence automatic prettyprinting of source, which enforced a standard layout and avoided the ghastly mess that was the usual appearance of a program of any size in the interpreted BASICs of the time. Programmers normally would cram as many lines together as possible to avoid line number memory overhead—not a problem in BASIC09 See also COMAL was another BASIC-like language with structured programming constructs Notes References Citations Bibliography External links Early OS-9 History, select content from 68 Micro Journal, September 1980, first review of OS-9 and Basic09, sent in by Tom Harmon of HHH Enterprises The Official Basic09 Tour Guide, Dale L. Puckett, 1985, , Cat No.: 26-3189 Package: Basic09 1.1.0 / Release Date: January 5, 2003, ''This release of Basic09 for the Tandy Color Computer 1/2/3 represents the first community-based release since the discontinuation of the CoCo in the 1980s. TRS-80 Color Computer BASIC interpreters