Break-disable



Robert Newman,

Peterborough,

Northamptonshire.



I have written two machine-code routines for the Spectrum

which disables the Break key during the running of a Basic

program - i.e., preventing the errors "BREAK into program"

and "BREAK - CONT repeats" from halting the program.

  Routine A also causes the computer to reset when the

program finishes, or if any error apart from Break occurs.

This would be useful if you want to prevent people from

listing or copying your program. however, unless your

program is on a Microdrive, it could always be Merged

instead of Loaded to overcome this.

  Routine B just disables Break, so that if the program

stops for any other reason it can be listed, edited, Run

etc.

  Put the lines of Basic from listing 1 at the beginning

of your program, using the DATA statements for either

routine A or routine B. Both routines can be used with 16K

or 48K. You only need to change the CLEAR statement in

line 2, and the value of start in line 3. [On the TZX,

"listing 1" has been saved along with the DATA lines for

the respective routines under the names "Routine A" and

"Routine B".]

  If you only want to disable break during certain parts of

your program, then miss out lines 5 and 6, and use the two

POKEs later when you want to switch break-disable on. Break

can then be re-enabled with these two POKEs:

        POKE errsp,3: POKE errsp+1,19

[Mr. Newman also provided a demo for each routine. These

are on the TZX as "Demo A" and "Demo B". The demos only

work under 48K, but can be easily changed for running on

a 16K machine as described above.]