Assignment  Statement
   The Assignment  Statement in FORTRAN assigns a value to a variable.
   The general form is:       
                      variable = expression
Exception
-   integer values can be assigned to real variables
-   real  values can be assigned to integer variables
 Example:
INTEGER  M , N
REAL  A , B
A = 6.2
B = A + 9/2
M = B
N = B + 1.6
A = N
A = M + N
N = A + B
M = N + 3 **3.0