Program Scanner



Don Scarrott,

Workington,

Cumbria.



When debugging a program, you often need to know where and

how a particular variable is used. It is very difficult to

be sure you have identified every occurrence yourself, so I

tried to write a Basic program to do the search for me. It

worked, but was dreadfully slow, taking some 10 minutes to

scan a long program.

  This machine-code version is much shorter, and is as fast

as the normal listing. It scans the program lines, skipping

REM and DATA lines, rushing past anything between quotes,

jumping over the embedded numbers, converting upper to

lower case, and comparising names to what you have placed

in z$. If they match, that line is printed.

  The machine code is located at 63929 with a length of

291. To use it you merely set the variable name into z$,

and RANDOMIZE USR 63929. It will then list all the lines

containing that variable on the screen.

  [We'll skip the program entry instructions - that's been

done. Here's how to use the resulting tape (or TZX):]

  Load your target program, enter

        MERGE ""

and start the prompter tape. Stop it as soon as the Basic

part has loaded. Enter

        GO TO 8692

and start the tape again. When the code has loaded, the Z$

prompt should appear. Enter the variable name of interest,

and watch the lines scroll up the screen.

  If you want hard copy, get out of the loop by deleting

the quotes and entering STOP. Then enter

        OPEN #2,"p"

and

        GO TO 8694

to re-enter the loop.