Chapter 2: TI-83 Plus Specific Information 111
TI-83 Plus Developer Guide Third Release May 28, 2002
Fig. 2.15 illustrates the location in RAM the temporary information is stored.
The data area for temporary variables is
located between User Memory (user data
storage) and the Floating Point Stack. It is
deliberately separated from user data so
that all of the temporary data area can be
deleted with no effect on user data storage.
The first byte of temporary storage is at
address (TempMem) and the last byte is at
(FPbase) - 1.
The symbol table entries
for temporary variables
are separated from all of
the other entries. The first
byte of the temporary
symbol table is at (Ptemp)
and the last byte is at
(Opbase) + 1.
System RAM
(Fixed Size)
User RAM
(Grows Up)
Temporary RAM
(Grows Up)
Floating Point Stack
(Grows Up)
Free RAM
Operator Stack
(Grows Down)
Symbol Table
(Grows Down)
Hardware Stack
(Fixed Size)
Addr
8000h
FFFFh
Temporary Variable
Symbol Table
User Symbol Table
Fig. 2.15: TI-83 Plus System RAM
Using Temporary Variables
Temporary variables can be used the in the same manner as any user variable. They
can be modified, resized, used to store in to a user variable, and input to system
routines.
These variables are called temporary as they are not intended for long term use. Their
main purpose is to provide a way to hold onto intermediate results dynamically as the
results are needed. Temporary variables should be freed up as soon as they are no
longer needed. Some system routines will automatically free up temporary variables if
they are used as inputs (this information is noted in the System Routine
Documentation).
Managing Temporary Variables
The life span of a temporary variable is determined by the application. Once a
temporary variable is no longer needed, it can be marked dirty by the application.
Marking a temporary variable dirty identifies it for deletion. Deleting the temporary
variable frees the RAM space it occupied.
This marking scheme is used to save time while parsing an equation. The
parser/executor does not use time deleting temporary variable — it only marks the
temporary variable for deletion after the variable is no longer needed.
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