Texas Instruments TI-92+, Tip List

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[7.19] Bypass programs locked with ans(1) and 4
→
→ →
→
errornum:passerr
It is possible to prevent viewing TI BASIC source code. First, put this near the beginning of the
program:
ans( 1 )
From the command line, execute:
4 → errornum:passerr
then run the program. Now, you cannot view the program beyond the ans(1). Further, if you try to edit
the program, all the 'invisible' code is lost. If you want to look at the source of a program 'locked' like
this, to determine if it may contain a virus or poor programming practices, Frank Westlake provides this
work-around:
1. Make a copy of the TI program on your computer so you won't have to remember how to undo
the changes (it may not run with the changes).
2. Open the copy with a PC hex editor and go to the 14th byte from the end of the file. Count the
last byte as one, second to the last as two, etc., until you get to 14.
3. Change byte 14 to hexidecimal 87, and change byte 13 (next one towards the end) to
hexidecimal 3A.
4. Save the file and open it in Graphlink.
5. If there doesn't appear to be anything to worry about, delete the copy and load the original.
Frank also says:
"I just used this procedure to check a whole groupfile of programs and if worked well. When I edit
disabled one of my own programs I had to use a more complicated method, so you might have to
experiment some. A knowledge of the file structure is extremely helpful so you may want to download a
document describing it from one of the archive sites. It also helps to compare the file to one that isn't
disabled. If I get time later this summer I'll try to come up with something more reliable."
(Credit to Frank Westlake)
[7.20] Running programs within a program
Suppose you have a program name stored as a string in variable pname. You can execute that
program like this:
expr(pname)
Note that the pname string must include the parenthesis. For example, if the program name is foo, then
pname is "foo()"
If the program is not in the current folder, you need to specify the folder like this:
expr(fname&"\"&pname)
where fname is the folder name string. If the folder name is known at execution time, you can just use
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