Source files (.c files)
C function definitions are placed in source files that have names ending in “.c”.
All functions normally may be accessed (called) by any other function in any file.
A function definition may be preceded by “static” to restrict access so that it may be called only by other functions defined in the same file.
External (“global”) variables may be defined in a .c file outside any function.
- External variables are created when program execution begins;
- they retain their values until execution of the program terminates.
- External variables may also be defined static in order to restrict access to them to the file containing the variable definition.