Well I've just used some Print Commands and Stop Commands to see what the program is doing ... and I unfortunately got my original fields mixed up, which wouldn't have helped anybody, these are not the 0 or -1 values !!! The values for this field are always (in this run anyway), 1,3, 4 or 6 and whenever it is equal to 1 then the command is found to be true. So I'm now going to try a small file of the numbers 0-99 and see if it is still only when it is equal to 1 that the command is deemed to be true.
If that is the case then I will assume that the command
... which is not only clearer but shorter to code in the first place
Thanks for answering rocket-dog, but as you can see, whilst I have done a similar process to what you suggested, it still leaves me speculating that that is what the command actually *really* does !!! I have a manual which I downloaded called the GFA Basic Manual, but it's 19 years old & this variation on the IF command isn't mentioned at all, so if anybody can point me at a newer / better manual, that would be appreciated