TI-83 series
The TI-83 is a popular graphing calculator that is manufactured by Texas Instruments.
It is one of the more popular graphing calculators for students (especially those in middle school or higher). It includes many different features and functions, including function graphing, polar/parametric/sequential modes, statistics, trigonometric, and algebraic functions, and many functions present on normal scientific calculators. Although it does not include as many calculus functions, applications (for the TI-83 Plus -- see below) and/or programs can be downloaded from various websites that allow for them.
The TI-83 was replaced by TI with the TI-83 Plus calculator in 1999, which included Flash ROM, enabling the device's operating system to be updated if needed, or for large new Flash Applications to be stored, accesssible through a new (Apps) key. The flash rom can also be used to store user programs and data. In 2001 the ante was raised with the TI-83 Plus Silver Edition, which featured approximately nine times the available Flash ROM, and twice the processing speed (12 MHz) of a standard TI-83 Plus, all in a translucent, iridescent grey case.
The original TI-83 is itself an upgraded version of the TI-82.
An interesting historical note: the TI-83 was the first calculator in the TI series to have built in assembly language support. (The TI-85 and TI-82 had ASM support, but only after sending a specially constructed (hacked) memory backup.) The support could be accessed through a hidden feature of the calculator. Users would write their assembly (ASM) program on their computer, compile it to a hexadecimal form, and send it to their calculator as a program. The user would then execute the command "Send(9prgmXXX", and it would execute the program. Successors of the TI-83 replaced the Send(9 backdoor with a less-hidden Asm( command.
The TI-84 Plus line was introduced in mid-2004 as a further update to the TI-83 line; the TI-83 is still available for purchase, but support for it is dwindling.