All that is required to write TI-BASIC is a TI calculator. It can be purchased at a brick-and-mortar store, or online at the Texas Instruments website. Z80, the version of TI-BASIC covered in this book, is used on TI-83, TI-83+, TI-84+, TI-83+ Silver Edition and TI-84+ Silver Edition calculators.
It is also possible to use a virtual calculator, or emulator, to program and test TI-BASIC programs without a calculator. Virtual TI was one of the first emulators for TI calculators. Wabbitemu is currently the best free Z80 emulator, for both Windows and Mac users. To use an emulator, a ROM image is needed. It is a "snapshot" of the current state of a calculator. Wabbitemu can generate its own image, however, a ROM image can be obtained from any calculator using one of these methods. Texas Instruments has created its own excellent and all-inclusive emulator/debugger for the TI-83 and TI-83 Plus calculators, called TI-83 Plus SDK, as it is free for anyone who registers their owned TI calculator, and is found here, along with other Texas Instruments software.
The main advantage of using an emulator is that, while it may be convenient to write a program and test it on the fly on an actual calculator, it is faster to type-up code on a computer to test with an emulator. An added advantage is the ability to include lower case letters on TI-83 Plus calculators, though not on regular TI-83 calculators.
A common application for programming TI BASIC on the computer is TI Edit. It allows the user to program as they would on a calculator, with built-in menus and functions. The drawback, however, is that TI Edit cannot run code. It can, however, save the code as a file that can be transferred to a calculator. The better thing to do is to use an emulator to test the programs you write before you transfer them onto a calculator. Remember to always backup your calculator before the transfer, because there is a small chance that the program will crash the operating system.
Normally, when buying a TI calculator, a CD is included with the set that includes computer software for coding on a computer and sending files to and from computers via a TI PC Link cable (not included). The link software provided by Texas Instrument is called TI-Connect, while the included program writing software is called TI-Graph Link, which can also be used as a linking program, but is out of date.
Other free 3rd party software can be found at ticalc.org, which has a large community of TI calculator owners and programmers. This specific page in ticalc.org's directory contains a large list of Windows, MAC, and UNIX related software.