Structure of the program part

We already know that each F77 code starts with the statement program, followed by the name of your code and ending with statement end. These two lines serve as an envelope of your program which is filled by the instruction code. Below is the structure of a typical F77 program:

          program MY_PROGRAM 
declaration of variables 
definition of parameters 
initial definition of variables 
instruction part 
end

Go back and try to identify the four parts above in our program for the calculation of the factorial.

In the following sections, we explain the meaning of each individual part in the scheme above. We will proceed from top to bottom, in the same order which you follow when writing your code. Programming is an abstract yet still very logical process in which all individual parts have their unique functions. To pass an information from one part of your code to the other, F77 uses various data structures, some of which will be explained thoroughly in subsequent lines.