Multi-File Programs

• C/C++ programs typically comprise multiple files
• A typical small program would have a header file, an implementation file, and a client file
• The header file has a .h extension, and it usually contains variable and function declarations
• More about header files...
• The implementation file has .C extension, and it contains the variable and function definitions
• The client file also has a .C extension, and it contains the client functions that calls the functions in the implementation file. Usually, this file contains the main() function.
• This multi-file structure has several advantages:
• Simplified organization of the program
• Reduction in compilation time because each file is compiled separately
• Only those files that have been modified need be re-compiled
• Makes it easier to debug large programs
• The Process:
• Compile each source file separately using the -c compiler option
• Link the object files to create one executable file
• Run the executable
• Example:
  g++ -c function.C
  g++ -c main_client.C
  g++ function.o main_client.o
  a.out
  
• This process can be automated using the UNIX make utility
• More about variable and function scope...
• Example of a multi-file program...