c     This program finds the sum of the squares of the first 100 integers
c     You should declare the type of EVERY variable you use
      PROGRAM SumOfSquares
      INTEGER:: i       ! i is an integer variable 
                        ! the double colon syntax is from f90, but g77 understands it 
      REAL:: sum        ! sum is a single precision floating point variable
      sum=0             ! initisalise sum
      DO i=1,100        ! this runs i over the first 100 integers
         sum=sum+i**2   ! this increments the sum.  Indent inside control loops for clarity of code  
         END DO         ! DO ... END DO is a fortran 90 construct that g77 understands
      WRITE(UNIT=*,FMT=*)  " The total is = ", sum
      END PROGRAM SumOfSquares