Hi there,
I've tried all I could in order to complete a very simple and basic program that finds the roots of any quadratic binomial.
You have to enter the coefficients a, b and c and it would find the roots. I could do that, but a problem occurred if I typed a=0. Of course if a=0 the binomial is not quadratic (and not even a binomial), so I wanted to let it know to the user of the program. Here my problems started... I don't know how to insert in my program that if a=0 then a message would appear saying that it isn't a quadratic binomial.
Here it comes :
Program findroot
implicit none
Real(8) :: a,b,c,delta,z,y,g
Write(*,*)'Enter a, b and c'
Read(*,*)a,b,c
if (a=0) then
write(*,*)'This is not a quadratic binomial'
endif
delta=b**24*a*c
If (delta>=0) then
z=(b+sqrt(delta))/(2*a)
y=(bsqrt(delta))/(2*a)
Write(*,*)'The roots are',z,y
Elseif (delta<0) then
write(*,*)'The binomial has no root in R but in C its roots are',b,'+i',sqrt(delta)/(2*a),'and',b,'i',sqrt(delta)/(2*a)
endif
End program findroot

I'm almost sure that I cannot type endif and then type if...
But I tried many other things like
if (a=0) then
write(*,*)'This is not a quadratic binomial'
delta=b**24*a*c
elseIf (delta>=0) then
z=(b+sqrt(delta))/(2*a)
y=(bsqrt(delta))/(2*a)
Write(*,*)'The roots are',z,y
Elseif (delta<0) then
write(*,*)'The binomial has no root in R but in C its roots are',b,'+i',sqrt(delta)/(2*a),'and',b,'i',sqrt(delta)/(2*a)
endif

and changing the order of the if statements... I always get errors and the program doesn't compile.
Any help is appreciated.
Note: If I erase the if (a=0) statement the program works well. (it compiles and find roots unless I type a=0).