120 Chapter 3: Application Development Process
TI-83 Plus Developer Guide Third Release May 28, 2002
PROGRAMMING LAYER
Chapter 2 covered the Hardware layer, the Driver layer, and the Tools and Utilities layer.
The final layer in the TI-83 Plus architecture is the Programming layer.
There are three kinds of programs that can be created for the TI-83 Plus: TI BASIC
programs, ASM programs, and Applications. This chapter is primarily concerned with
applications. In the following discussion, Z80 refers to the type of microprocessor used
by the TI-83 and TI-83 Plus.
TI-BASIC Programs
These programs were available on the TI-83 and may be known as scripts or keystroke
programs. These programs are created using the PC program TI GRAPH LINK for TI-
83 Plus or directly on the calculator using the [PRGM] New [1:Create New] options. The
details for creating this kind of program are provided in the TI-83 Plus Guidebook.
These programs consist of commands that mimic the calculator keystroke commands,
plus some additional keywords for control-flow logic. These programs are loaded into,
and run from, the calculator RAM. There must be sufficient free RAM available in order
to be able to load a TI BASIC program. This language is interpreted, so these programs
do not have to be assembled or compiled before you run them on the calculator.
Interpreting the programs, however, causes them to be relatively slow. When these
programs execute, if they contain an illegal statement or perform an illegal operation,
the interpreter stops the program and displays an error message. The calculator
functions normally after such an error.
ASM Programs
ASM programs were available on the TI-83 and may be known as assembly programs
or ASAPs. These programs are written in Z80 assembly language and then adapted to
use the calculator’s pre-existing ability to run TI BASIC programs. After the ASM
program is assembled, it is converted to a readable text format that can then be
downloaded to the calculator in the same way as a TI BASIC program. A special
keyword at the start of the program tells the calculator interpreter that it is an ASM
program instead of a normal TI BASIC program. The interpreter then converts the
program into Z80 machine language and gives it control of the processor. Since these
programs have total control over the calculator, they are fast, but any programming
errors can be serious, causing the calculator to become unusable until reset. These
programs are able to call built-in calculator routines. They run in RAM and are limited in
size to 8K.
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