fortran 77 example

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          program function1
c --- declaration of variables
          real x, y
c --- show function
         print*,"=========================================="
         print*,"Calculate the function y = f(x) defined as"
         print*,"           y = x+1 if x < 1"
         print*,"           y = 2-x if x >= 1"
         print*,"=========================================="
c --- request x as input
         print*,"enter a value of x:"
         read*,x
c --- evaluation of function
        if (x.lt.1.0) then
           y = x+1
        else
          y = 2-x
        end if
c --- print result
        print*,"the corresponding value of y is: ",y
c --- end program
        end