The TI-99/4A put a full typing keyboard on Texas Instruments’ home-computer design in 1981. It followed the TI-99/4 introduced in 1979, so a date for the earlier machine is not the /4A’s release date. The Centre for Computing History’s catalogued example identifies the revised keyboard and display chip among the changes.
For an owner, the immediate choices were TI BASIC and cartridge modules. BASIC supplied a place to type, edit and run programs; a module supplied software through the slot beside the keyboard. Adding a different language or application did not necessarily mean replacing the computer’s built-in environment.
Drawing with character patterns
TI’s User’s Reference Guide builds graphics from screen positions, colours and character patterns. CALL CHAR defines a character’s dot pattern. Horizontal and vertical character-writing calls can fill regions with repeated shapes. The same screen vocabulary can serve letters, borders and game objects. (Original TI guide.)
That BASIC environment should be distinguished from everything the display hardware can do. The TMS9918A supports hardware sprites, but the base TI BASIC command set does not expose the sprite commands provided by Extended BASIC. TI’s Extended BASIC course contents, p.3, lists CALL SPRITE and its related operations in separate sprite chapters. Seeing a capability in a chip specification does not establish that a program can request it through the language supplied with the machine.
Memory descriptions need the same care. The display’s 16KB of video RAM is not a 16KB general-purpose CPU workspace. A program’s route to the display depends on the hardware and the environment in which it runs.
Expansion changed the system
The guide treats cassette storage, modules and peripheral equipment separately. C. Regena’s December 1983 COMPUTE! column shows how substantial an expanded setup could become: the peripheral expansion box, disk drive and controller, memory expansion and serial interface were distinct purchases. Her quoted offers describe that period’s market, rather than the contents of every TI-99/4A box. (Contemporary column.)
The distinction matters when reading software requirements today. A program for base TI BASIC, one for Extended BASIC and one requiring expanded machine-code facilities can all be associated with the TI-99/4A while expecting different equipment. Its relationship to the MSX through related video hardware likewise does not make their cartridges or programs interchangeable.
Sources
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Texas Instruments, User’s Reference Guide (1981). Copyright 1979–1981; TI-99/4A guide, BASIC graphics/sound, modules and peripherals. Read source.
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C. Regena, Programming the TI, COMPUTE! (1983-12). Issue 43, p.252; contemporary expansion equipment and costs. Read source.
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Centre for Computing History, TI-99/4A. Held-object catalogue; 1981 model and keyboard/display changes. Read source.
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Texas Instruments, Teach Yourself Extended BASIC, p.3, chapters 5–6: positive documentation of the Extended BASIC sprite calls. Original manual.