To use, just transfer all five programs to your calculator and run ZCALC
from in Doors CS.

You may enter just about anything to be evaluated; for example:

4-(9*7) would return -59
For the most part, TI-OS syntax errors are avoided.

However, there are some more useful commands, rather than such boring
'fixed' arithmetic operations.  Each of these commands are provided by
a plugin program.  Included are ZRECALL, ZSETNUM, and ZGRAPH.
Provided commands:

Command invocation	| Provided by	| Notes
SET [0-9],x		 ZSETNUM	 x may be any number or expression, sets a variable
[x]			 ZRECALL	 x is a digit from 0-9, and the corresponding numbered variable is substituted for the expression (so if var 0 is pi and you enter "5[0]^2", it would become 5(pi)^2)
GRAPH function		 ZGRAPH		 graphs function on the coordinate plane, then pauses
ZOOM [IN,OT,ST,NT]	 ZGRAPH		 Zooms the graph screen in (IN), out (OT), to standard (ST), or to integers (NT)