When in programing mode XEQ function is programed and when the program finds the XEQ function it changes to the given program which must finish with RTN function.
So LBL “label” and RTN makes a kind of procedure and after the procedure is run it goes back to the previous position.
Example:
01 LBL S
02+
03RTN
04LBL A
055
06ENTER
077
08XEQ S
091
10-
11.END.
This program called “A” creates a procedure “S” which does only a simple addition. In the line 07 the XEQ “S” makes the program to go to the procedure “S” and after that it goes back to the line next line 07 which is of course the line 08. The calculation is
You can use programmed GTO and XEQ even to call a label in another program space but this is not exactly a good use.
6.3 The X?0 and X?Y sub-menus.
Up to now we saw nothing about how we could do a IF instruction, like what we have in computer's programming languages like BASIC, Pascal or C.
In fact there is no IF, THEN, ELSE, ELSEIF, etc in the
12 test functions which are:
X=0?, X≠0?, X<0?, X>0?, X≤0?, X≥0?
and
X=Y?, X≠Y?, X<Y?, X>Y?, X≤Y?, X≥Y?
The first group of functions involving the number 0 is accessed by the X?0
How do these functions work? Let's consider the first function “X=0?”. If the number in the first line of the stack (line x) is zero than the program works normally and it goes to the next line after “X=0?” instruction. But if the condition is not true than the program jumps the next line and goes to the second line after the instruction. Usually the line after the instruction has a GTO “label” command and this makes the difference in the program flux.
All the other functions involving the 0 work in the same way. If the condition is true the program