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## Fortran 90 very basic question : else if statement

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**2-4*a*c If (delta>=0) then z=(-b+sqrt(delta))/(2*a) y=(-b-sqrt(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**2-4*a*c elseIf (delta>=0) then z=(-b+sqrt(delta))/(2*a) y=(-b-sqrt(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).

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