Tymshare SUPER BASIC

SUPER BASIC, sometimes SBASIC for short, is an advanced dialect of the BASIC programming language offered on Tymshare's SDS 940 systems starting in 1968 and available well into the 1970s.

Like the Dartmouth BASIC it was based on, SUPER BASIC was a compile and go language, as opposed to an interpreter. In addition to offering most of the commands and functions from Dartmouth BASIC Version 4, in including matrix math commands, SUPER BASIC also included a number of features from the seminal JOSS language developed at Rand Corporation, via Tymshare's version, CAL, and added a variety of new functions, complex numbers as a built-in type, and double precision support.

SUPER BASIC also greatly improved string handling over the rudimentary system in Dartmouth, introducing the , and string functions, simple string concatenation and other features. These were later used in DEC's BASIC-PLUS, which was later used as the basis for the original Microsoft BASIC that saw widespread use in the 1980s.

History

The original Dartmouth BASIC was released in 1964 but was largely experimental at the time. It went through several revisions before becoming truly useful with the Fourth Edition when it was ported to the GE 635 machine and was published in 1968. Dartmouth specifically placed the underlying design in the public domain, so that anyone could port it to their platforms and call it BASIC. Its spread was further helped by the tireless efforts of its authors to promote it. However, as the code was designed to run on the DTSS operating system, some porting was required to run it on production systems. This led to a proliferation of versions with minor differences.

Tymshare was formed within the University of California, Berkeley, initially renting out time on the University's computers on off-hours. Tymshare's original BASIC, simply Tymshare BASIC, was based on source code "from elsewhere" in the University, that Dan Lewis began enhancing. Frank Bracher added the routines for file input/output (I/O), which made it far more practical than the original Dartmouth code that relied purely on statements embedded in the program. Dartmouth's workflow was tape based so loading and saving individual files was not practical and direct I/O was not addressed until later versions. Bracher's I/O code had originally been developed for Tymshare's SUPER FORTRAN offering.

One oft-noted feature of the system was the documentation, written by Caroline Diehl. The manuals were written in a conversational style.

Tymshare maintained SUPER BASIC through the 1970s, but as the market for rented timeshare programming services dwindled the system went into maintenance and Lewis and Bracher left to do SUPER BASIC consulting for those companies still using it. Maintenance within Tymshare passed primarily to Walter Main.

Tymshare filed for a trademark on SUPER BASIC on 7 January 1970, and refreshed it on 17 October 1977, which became the property of McDonnell Douglas in 1984 when the company purchased Tymshare.

Language

Direct and indirect mode

Like most BASIC systems of the era, SUPER BASIC had a single command line editor that worked both as an interactive language and a program editor. Commands that were typed without a line number were executed immediately, which they referred to as "direct mode". If the same line was prefixed with a line number, it was instead copied into the program code storage area, known as "indirect mode". New lines were added to the program if the line number was unique, replaced existing lines with the same number, or removed from the program if an existing line number was typed in without any code following it.

Program statements

Line numbers ran from 0 to 999999. The (or short-form ) could be used to delete a range of lines using typical notation, for instance, . The command started an automatic line-number system. It took two optional parameters, a starting line number and a step, separated with . The starting number was assumed to be zero if not provided, and the step was 10. For instance, would produce 0,10,20,..., would produce 0,5,10,..., and would produce 10,20,30... took three parameters, a new starting line number, a range of lines to renumber (like 20-100) and the step.

Although the built-in editor loaded and saved only the lines in the program itself, the user could edit the resulting text file to add additional commands that would run in direct mode. A common example was to edit a program and add on its own line at the end of the file. When loaded, the system would see the and immediately compile and start the program on loading. This is unusual for BASIC systems, although this was commonly used in JOSS.

Statements

In keeping with the overall Dartmouth BASIC concept, SUPER BASIC was a compile and go system that compiled the source code when the program was run. SUPER BASIC had two commands for this, the typical seen in most BASICs, as well as which did the same thing. Remarks could be placed anywhere using .

SUPER BASIC expanded the statement in several ways. A minor change was to allow in place of , and allowed the step to be placed at the end as in most BASICs, or in the middle as in JOSS and other languages. Thus and were both valid. Additionally, SUPER BASIC provided alternate forms of the range definition using and , whereas most other languages used completely separate loop structures for these. For instance, will continue as long as XMicrosoft BASIC