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# TI-89 series

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The TI-89 and the TI-89 Titanium are graphing calculators developed by Texas Instruments.

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## The original version: TI-89

The TI-89 is a graphing calculator developed by Texas Instruments (TI) in 1998. Possessing a 160×100 pixel resolution LCD screen with advanced flash memory, coupled with TI's Advanced Mathematics Software, the TI-89 is dwarfed only by its larger and slightly more powerful cousin, the Voyage 200.

The heart of the TI-89 is the Motorola 68000 microprocessor, which, depending on the calculator's hardware version, runs at 10 MHz or 12 MHz. Texas Instruments has allocated 256 KB of the total RAM for the unit (190 KB of which are available to the user) and 2 MB of flash memory (700 KB of which is available to the user). The RAM and Flash ROM are used to store expressions, variables, programs, tables, text files, and lists.

In the summer of 2004, the TI-89 was replaced by the TI-89 Titanium.

### User features

The TI-89 is essentially a TI-92 Plus with a limited keyboard and smaller screen. It 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, some people found the TI-92 unwieldy and overly large. The TI-89 is significantly smaller. It has a flash ROM, a feature present on the TI-92 Plus but not on the original TI-92. The TI-89 is not permitted on the ACT, although it is permitted on the SAT examinations.

The major advantage of the TI-89 over lower-model TI calculators is its built-in Computer Algebra System, or CAS. The calculator can evaluate most algebraic expressions and solve for the unknowns. For example, if asked to expand the expression a*(2+c) it returns $a \cdot c + 2 \cdot a$. If it is asked to evaluate ∫(x+1,x), it returns $\frac{x^2}{2} + x$. It can also solve systems of equations; for example, solve(x=y+7 and y=x/3,{x,y}) gives $x=\frac{21}{2}$ and $y=\frac{7}{2}$. 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 $\frac{x+y}{7^a}$.

In addition to the standard two-dimensional function plots, it can also produce parametric plots, polar functions, sequence plots, differential equation fields, and three-dimensional graphs.

### Programming

The TI-89 is directly programmable in a language called TI-BASIC, TI's derivative of BASIC for calculator applications. Using a PC, one can also develop one's own programs in Motorola 68000 assembly language or C, translate them to machine language, and copy them to the calculator. Two software development kits for C programming are available; one is TI Flash Studio, the official TI SDK, and the other is TIGCC, a third-party SDK based on GCC.

Since 1998, thousands of programs for math, electronics, biology, or entertainment have been developed. Many available games are generic clones of Tetris, Minesweeper, and other classic games, but some programs are more advanced — for example, a ZX Spectrum emulator and a chess playing program.

## TI-89 Titanium

The TI-89 Titanium was released in the summer of 2004, and is positioned as a replacement for the popular (but now low-margin) TI-89.

The touted advantages of the TI-89 Titanium over the TI-89 are having roughly four times the available flash memory (with over three times as much available to the user). The TI-89 Titanium is essentially a Voyage 200 without an integrated keyboard, but with a mini-USB port for connectivity to other (TI-89 Titanium) calculators or to computers to add programs or update the operating system (also called the AMS - Advanced Mathematics Software). The TI-89 Titanium also features some pre-loaded applications, such as "CellSheet", a spreadsheet program also offered with other TI calculators. The Titanium also has a case design different from that of the TI-89.

There are some minor compatibility issues with C and assembly programs developed for the original TI-89. They will have to be recompiled to work on the Titanium due to various small hardware changes. In some cases, only one character needs to be changed (the TI-89's ROM base is at 0x200000, whereas the TI-89 Titanium's is at 0x800000).