Introduction to C ++

Preprocessor directives are not program statements but

directives for

PREPROCESSOR

DEFINITION

• #define• #undef• #ifdef• #ifndef• #error

AVAILABLE

• #pragma

• #if• #endif• #else• #elif

#define identifier replacement

#define

#define PI 3.14159

const float PI = 3.14159;

#include<iostream.h>

#define PI 3.14159void main(void){

const float pi = 3.14159; cout<<"PI: "<< PI <<endl<<endl; cout<<"pi: "<< pi << endl << endl; cout<<"pi*PI: "<<pi*PI<<endl<<endl;

} // main function ends here

EXAMPLEPI: 3.14159

pi: 3.14159

pi*PI: 9.86958

#define square(x) (x)*(x)

DEFINING MACROS

#define m-identifier replacement

double square(double x){return x*x;}

EXAMPLE#include<iostream.h>

#define square(x) (x)*(x)double sqr(double x){return x*x;}void main(void){ int value = 9; cout<<"Square of "<<value<<" is: "<<square(value)<<endl;

cout<<"Square of "<<value<<"+1 is: "<<square(value+1)<<endl; cout<<"Square of "<<value<<" is: "<<sqr(double(value));

}// main function ends here

Square of 9 is: 81

Square of 9+1 is: 100

Square of 9 is: 81

OUTPUT

Square of 9 is: 81

Square of 9+1 is: 100

Square of 9 is: 81

Questions &

Answers

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