1. Introduction to Programming
Lecture 23
Preprocessors and Header files

2. Today’s Lecture
Preprocessor Directives
Header Files
Macros

3. Preprocessor

4. #include <iostream.h>

5. #

6. #include #include <iostream.h> #include <stdlib.h>
#include <fstream.h>
#include <stream.h>

7. 5:10 to 5:23

8. 5:24 to 5:41

9. Re-locatable Executable

10. MyHeader.h

11. #include “MyHeader.h”

12. #include <iostream.h>

14. #define

15. #define PI

16. Preprocessor Directives
#if
#else
#endif
#elif
#ifdef
#ifndef
#error

17. Preprocessor Directives
#ident
#import
#line
#machine
#system
#warning

18. Example
#ifdef PI

19. # define PI
# ifdef PI

20. # define DEBUG
# ifdef DEBUG

21. Conditional Compilation Macro Translation

22. #undef DEBUG

23. #include <conio.h>
#include <conio.h>
Consol Input Output

24. #include <conio.h> #include <conio.c>

25. int getche ( ) ;

26. Get Character With Echo

27. #ifdef __cplusplus
extern "C" {
#endif
- - }

28. Macro

29. Example 1 #define SQUARE ( X ) X * X main ( ) { int i = 5 , j ; : }
i * i ;
SQUARE ( i ) ;

30. Example 2 #define SQUARE ( X ) X * X main ( ) {
int i = 5 , j = 10 , k ; :
k = }
i + j * i + j ;
SQUARE ( i + j ) ;

31. Example 3 #define SQUARE(X) (X)*(X) main ( ) {
int i = 5 , j = 10 , k ;
k = }
SQUARE ( i + j ) ;
( i + j ) * ( i + j ) ;

32. Overhead

33. Code Bloat

34. Example 4 #define PI 3.14159 #define CIRCLEAREA ( X ) main ( ) {
float radius ;
cout << “ Enter radius of Circle Area : ” ;
cin >> radius ;
cout << “ Area of Circle Area is ”
<< }
( ( PI ) * ( X ) * ( X ) )
PI * X * X
CIRCLEAREA ( 2 * radius ) ;
CIRCLEAREA ( radius ) ;
( ( PI ) * ( radius ) * ( radius ) ) ;

35. Header Files

36. Header File #include <iostream.h> #include <stdlib.h>
#include <stdio.h>
#include <string.h>

37. In Next Lecture
Memory Allocation