Once you have examined, compiled, and run the sample Fortran program, you probably have an idea what it does and how it works. But you still don't know much about the specific syntax rules for writing Fortran programs.
Before we get into a line-by-line discussion, however, let's take a closer look at the overall structures of the program rbtjnts.f. Note the generous use of comments. There is a preamble that describes the object of the program. The variable description section describes the named variables involved in the program. This is followed by the actual variable declaration. After the variable declarations, the actual program statements follows. We will discuss the individual statements in the program in the this chapter. The last program section before the end statement is the output section.