15 3. modulization
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The document discusses techniques for modularizing source code into separate files when developing large programs. It recommends splitting source code into multiple .c and .h files with each function defined in its own .c file and declared in a corresponding .h file. Header files should include function prototypes and extern declarations. Conditional compilation with #ifndef and #define is used to prevent header files from being included multiple times. This modular approach makes the code easier to maintain, compile and work on collaboratively.
15 3. modulization
- 1. Modulization
- 2. Developing a Large Program Developing a large Program – We can split source codes into several ~. h and ~.c files – There are many merits of several small files instead of one big file • Easy to maintain source codes • Easy to co-work with other programmers • Save time when compiling: You can just compile ~.c files which are modified not all of source codes. 2
- 3. 3 Modulization Split source code into separate files #define TWO 2 typedef void VOID ; int g; VOID func1(VOID) ; VOID func2(VOID ) ; VOID main(VOID ) { func1() ; func2() ; g *= TWO ; } file.c VOID func1(VOID ) { func2() ; g += TWO ; } VOID func2(VOID ) { func1() ; g -= TWO ; } To be written by friend 1 To be written by friend 2 To be written by me
- 4. 4 Modulization Split source code into separate files – Make ~.c files for each function – Add #define, declaration, function prototypes, extern objects Prototype of Functions #define TWO 2 typedef void VOID ; int g; VOID func1(VOID) ; VOID func2(VOID) ; VOID main(VOID) { func1() ; func2() ; g *= TWO ; } #define TWO 2 typedef void VOID ; extern int g; VOID func2(VOID) ; VOID func1(VOID) { func2() ; g += TWO ; } #define TWO 2 typedef void VOID ; extern int g; VOID func1(VOID) ; VOID func2(VOID) { func1() ; g -= TWO ; } file1.c file2.c file3.c
- 5. 5 Modulization Split source code into separate files – Problem – When you want to modify #define or typedef definitions • You should modify all of source files => Solution : Use Header file #define TWO 2 typedef void VOID ; int g; VOID func1(VOID) ; VOID func2(VOID) ; VOID main(VOID) { func1() ; func2() ; g *= TWO ; } #define TWO 2 typedef void VOID ; extern int g; VOID func2(VOID) ; VOID func1(VOID) { func2() ; g += TWO ; } #define TWO 2 typedef void VOID ; extern int g; VOID func1(VOID) ; VOID func2(VOID) { func1() ; g -= TWO ; } file1.c file2.c file3.c
- 6. 6 Modulization Split source code into separate files – Generally create one ~.h file for each ~.c file – Content of ~.c • Functions • Definition and Declaration used the functions in the file • #include header files necessary in the file – Content of ~.h • Extern definition of global variable accessed in the corresponding ~.c file • Prototype of function defined in the corresponding ~.c file • #include header files if necessary
- 7. 7 Modulization Split source code into separate files extern int g VOID func1(VOID) ; VOID func2(VOID) ; int g; VOID main(VOID) { func1() ; func2() ; g *= TWO ; } VOID func1(VOID) { func2() ; g += TWO ; } VOID func2(VOID) { func1() ; g -= TWO ; } file1.h file2.h file3.h file2.c file3.cfile1.c #define TWO 2 typedef void VOID ; def.h
- 8. Modulization Split source code into separate files – Include necessary ~.h files in ~.c and ~.h files file1.h file2.h file3.h extern int g #include “def.h” VOID func1(VOID) ; #include “def.h” VOID func2(VOID) ; #include “def.h” #include “file2.h” #include “file3.h” int g; VOID main(VOID) { func1() ; func2() ; g *= TWO ; } #include “def.h” #include “file1.h” #include “file3.h” VOID func1(VOID) { func2() ; g += TWO ; } #include “def.h” #include “file1.h” #include “file2.h” VOID func2(VOID) { func1() ; g -= TWO ; } def.h #define TWO 2 typedef void VOID ; file2.c file3.cfile1.c 8
- 9. Conditional Compilation Problem with relation of header files – Some header files are included more than once • Cause overlapped definitions – Solve with conditional compilation! file1.h file2.h file2.h file1.c file2.c file3.c def.h #define TWO 2 typedef void VOID ; 9 def.h is included twice “TWO” is defined twice
- 10. Conditional Compilation Conditional compilation based on #ifndef, #endif – Place all of content of header file between #ifndef and #endif – Insert #define UNIQUE_NAME 10
- 11. 11 Conditional Compilation #ifndef _FILE1_H_ #define _FILE1_H_ extern int g #endif #ifndef _FILE2_H_ #define _FILE2_H_ #include “def.h” VOID func1(VOID) ; #endif #ifndef _FILE3_H_ #defien _FILE3_H_ #include “def.h” VOID func2(VOID) ; #endif #include “def.h” #include “file2.h” #include “file3.h” int g; VOID main(VOID) { func1() ; func2() ; g *= TWO ; } #include “def.h” #include “file1.h” #include “file3.h” VOID func1(VOID) { func2() ; g += TWO ; } #include “def.h” #include “file1.h” #include “file2.h” VOID func2(VOID) { func1() ; g -= TWO ; } #ifndef _DEF_H_ #define _DEF_H_ #define TWO 2 typedef void VOID ; #endif file2.c file3.cfile1.c file1.h file2.h file3.hdef.h
- 12. 12 #ifndef _FILE1_H_ #define _FILE1_H_ extern int g #endif #ifndef _FILE2_H_ #define _FILE2_H_ #include “def.h” VOID func1(VOID) ; #endif #ifndef _FILE3_H_ #defien _FILE3_H_ #include “def.h” VOID func2(VOID) ; #endif #include “def.h” #include “file2.h” #include “file3.h” int g; VOID main(VOID) { func1() ; func2() ; g *= TWO ; } #include “def.h” #include “file1.h” #include “file3.h” static int g1 ; VOID func1(VOID) { func2() ; g += TWO ; } static VOID sfunc1(VOID) { } #include “def.h” #include “file1.h” #include “file2.h” static int g2 ; VOID func2(VOID) { func1() ; g -= TWO ; } static VOID sfunc2(VOID) { } #ifndef _DEF_H_ #define _DEF_H_ #define TWO 2 typedef void VOID ; #endif file2.c file3.cfile1.c file1.h file2.h file3.hdef.h