![]() ![]() ![]() For instance, BREAK 130 would cause the program to exit to immediate mode whenever it moved to line 130. Unlike STOP, the exit to immediate mode did not occur on the line where BREAK appeared, but on the lines BREAK referred to. BREAK worked something like STOP, stopping execution on certain lines. TI BASIC also included a number of debugging commands. Line entry was aided by the NUMBER command, available only in immediate mode, which entered ascending line numbers, and RESEQUENCE, which renumbered an existing program. Line numbers ranged from 1 to 32767, inclusive, and entering a line outside that range resulted in the "BAD LINE NUMBER" error. It used a > prompt to indicate the current new line in immediate mode, as opposed to the more common READY. Explicit line numbers were used to order each statement. Instead, a line editor was provided, which allowed the user to add or edit one line at a time. Unlike most BASICs of the era, TI BASIC did not provide a full-screen editor. Elements of TI BASIC Editing and running For instance, running the Byte Sieve in BASIC took 3960 seconds in TI BASIC, while the same test in Applesoft BASIC on the Apple II, ostensibly a much slower machine, took 2806 seconds, about 30% faster that the TI. As a result, TI BASIC had poor performance on common benchmarks of the era, the TI-99 generally ran half as fast as 8-bit machines like the Commodore PET or Apple II. Every instruction in the user's program had to be read from 8-bit memory, interpreted using code written in GPL, and then output back over the 8-bit bus again. This was particularly noticeable in BASIC. įor all of these reasons, the machine ran far slower than it was theoretically capable of. The GPL code itself was stored on the 8-bit side of the machine, further slowing its performance. The downside to this approach is that every GPL instruction had to be converted on the fly into one or more underlying TMS9900 instructions. To address this, TI created an 8-bit virtual machine with its own language or intermediate representation known as the "Graphic Programming Language", or GPL, that allowed programs to be written in a more compact format. In the era of expensive memory, this presented a significant cost. The TMS9900's instruction set architecture was based on 16-bit opcodes, meaning that programs would generally be twice as large as they would be on an 8-bit machine. TI thus adopted the solution of making the machine mostly 8-bit and connecting the various support chips to this 8-bit bus, with the TMS9900 reading the bus twice to produce a 16-bit value. In a minicomputer, 16-bit support systems were built up of many individual chips, but this was not suitable for a low-cost product. The TMS9900 was also suitable for use in a microcomputer, but at that time the rest of the support chips required to build a complete computer were invariably 8-bit, and this included TI's wide catalog of such chips. The TI-99 was based on the TMS9900 microprocessor, a 16-bit design that was originally built to provide a single-chip central processing unit (CPU) in low-end models of their TI-990 minicomputer lineup. Due to the specifics of the TI-99 platform, TI BASIC was most notable for its extremely slow performance, roughly half that of common machines, but conversely sported high numerical accuracy. On top of Minimal BASIC, TI added commands for text, graphics, and basic file operations like recording to tape or any other file system. This included a wide variety of features found in other BASICs, as well as new system functions for sprite handling, sound, and other features of the platform.Īs was common on home computers, TI BASIC was used not only for programming but also as a thin operating system. Minimal BASIC lacks a number of features that are commonly found on contemporary BASICs, and Texas Instruments later introduced the TI Extended BASIC cartridge that enhanced the functionality accessible to BASIC users. There are a number of differences, sometimes subtle, between TI BASIC and the more common MS varieties. This was, in turn, based on the original Dartmouth BASIC from the 1960s. In contrast to most BASICs found on contemporary microcomputers, TI BASIC does not trace its history to Microsoft BASIC, but was instead a TI-developed interpreter following the emerging Minimal BASIC standard being created by ANSI and ECMA. TI BASIC is an ANSI-compliant interpreter for the BASIC programming language built into the 1979 Texas Instruments TI-99/4 home computer and its improved 1981 version, the TI-99/4A. ![]()
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