I made a program that calculates the equation of an exponential with (X1,Y1) and (X2,Y2). The problem is that I noticed my program to verify that the difference between X1 and X2 is 1 and I want it asks to the user to re-type X1,Y1,… so it can calculates eqn, but it always asks me to re-enter those values ! There is my source code:

```
()
Prgm
ClrIO
setMode("Exact/Approx","APPROXIMATE")
setMode("Display Digits","FLOAT 6")
Input "X1:",a
Input "Y1:",b
Input "X2:",c
Input "Y2:",d
While c-a≠1 or a-c≠1
ClrIO
Disp "Difference between X1 and X2"
Disp "must be equals to 1"
Loop
Input "X1:",a
Input "Y1:",b
Input "X2:",c
Input "Y2:",d
EndLoop
EndWhile
While a<c
d/b→e
e^a→f
b/f→g
ClrIO
Output 1,1,y=g*e^x
setMode("Exact/Approx","AUTO")
setMode("Display Digits","FLOAT 12")
Stop
EndWhile
While a>c
b/d→h
h^c→i
d/i→j
ClrIO
Output 1,1,y=j*h^x
setMode("Exact/Approx","AUTO")
setMode("Display Digits","FLOAT 12")
Stop
EndWhile
EndPrgm
```

When I remove the statement from { While a-c != 1 […] to EndLoop , EndWhile } , my program works. If that statement is there, my program asks me to re-enter the values even if the difference between X1 and X2 is 1. Hope someone can help !

P.S: Sorry for my bad english :s