Use the -DD option to compile source lines containing user debugging statements. Debugging statements included in a program are indicated by the letter D in column 1. By default, the compiler takes no action on these statements. For example, to compile any debugging statements in program prog1.f, enter the following command:
prompt>ifc -DD prog1.f
The above command causes the debugging statement
D PRINT *, "I= ",I
embedded in the prog1.f to execute and print lines designated for debugging.