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# TI-89

The TI-89 (or TI89) is a powerful graphing calculator developed by Texas Instruments. It has a graphics LCD display with a resolution of 160x100 pixels. It has 256 kilobytes of RAM (190 of which are available to the user) and 2MB of flash memory (700KB of which is available to the user). The RAM and Flash ROM are used to store variables, programss, tables or even games. The heart of the TI-89 is the Motorola 68000 microprocessor, which on the hardware 1 version runs at 10MHz, but the hardware 2 version runs at 12MHz.

The TI-89 is fundamentally a TI-92 with a limited keyboard and smaller screen. The TI-89 was created partially in response to the fact that while calculators are allowed on many standardized tests, the TI-92 was considered a computer due to the QWERTY layout of its keyboard. Additionally, many disliked the TI-92 for its large size. The TI-89 is significantly smaller. The TI-89 has a flash ROM, a feature present on the TI-92 Plus but not on the original TI-92. However, the TI-89 is not permitted on the ACT, although it is permitted on the SAT examinations.

The biggest advantage of the TI-89 is symbolic manipulation (due to a Computer algebra system), which means that the calculator can evaluate algebraic expressions, even with unknowns in them. For example, in response to "a*(2+c)" it returns "2*a+a*c". If it is asked to evaluate "∫(x+1,x)", it returns "(x^2)/2 + x". It can also solve systems of equations; for example, "solve(x=y+7 and y=x/3,x,{x,y})" gives "x=21/2 and y=7/2". The TI-89 pretty prints algebraic expressions — that is, it represents expressions as they would be written on paper, not as they would be entered into a computer ("(x+y)/(7^a)" becomes "").

In addition to the normal two-dimensional plots of functions, it can also produce three-dimensional graphs and implicit plots.

The TI-89 is directly programmable in a language called "Keystroke", vaguely reminiscent of BASIC. Using a PC, one can also develop your own programs in Motorola 68000 assembly language and C, translate them to machine language, and copy them to the calculator.

Since 1998, thousands of programs for math, electronics, biology, or just for fun have been developed. Most available games are the generic clones of Tetris or Minesweeper, but some programs are really amazing — for example, a ZX Spectrum emulator and a chess playing program. There is also an on-calc development environment available. It is called ams-dev, and consists of an IDE, side; an assembly language (asm) compiler, as; a C compiler, cc; and a debugger, db92).