For example, to get and store the error number into variable e and then print it but still stop execution, we could modify the first program as follows:

10 ON ERROR PRINT "There was
   an error!": ERROR TO e:
   PRINT e: ON ERROR:STOP
20 PRINT 5/0

If we allow the program to finish and then use ERROR we would have gotten the 9 STOP statement, 10:5 error report which would be the last error report in statement 5 of line 10 as STOP is considered an error. But by using ERROR TO, we'll get 6 printed on screen which is the error code for the Number too big error

So far we have seen the keywords PRINT, LET, INPUT, RUN, LIST, GO TO, CONTINUE, STOP, ON ERROR, ERROR, ERROR$, ERROR TO, NEW and REM. Apart from ON ERROR you can also enter them as direct commands – this is true of almost all commands in NextBASIC. RUN, LIST, CONTINUE and NEW are not usually of much use in a program, but they can be used regardless.

Exercises

1. Put a LIST statement in a program, so that when you run it, it lists itself.

2. Write a program to input prices and print out the tax due (at 20 per cent). Put in PRINT statements so that the computer announces what it is going to do, and asks for the input price with extravagant politeness. Modify the program so that you can also input the tax rate (to allow for zero ratings or future changes).

3. Write a program to print a running total of numbers you input. (Suggestion: have two variables called total – set to 0 to begin with – and item. Input item, add it to total, print them both, and go round again.)

4. What would CONTINUE and NEW do in a program? Can you think of any uses at all for this?