#define

(4) Explain macro substitution directive?
Ans:

Syntax: #define [ ,, …]
Here [,,…] is optional.
When you use this in the program then in the program this is called macro and #define directive only replaces the macro by before starting of actual compilation.
e.g

#define pie 3.14
Void main()
{
float r=3,area;
area=3*r*pie;
printf(“%f”,area);
getch();
}

Before the starting of actual compilation an intermediate is formed which is :

We can see only in place of pie ,3.14 has pasted.
If is very long or we want to write in next line ,end first line by \.
e.g

#define word c is powerful \
language.
MACRO FUNCTION:

#include

(6) What is file inclusion directive or #include directive ?
Ans:
Syntax:

#include <>

or

#include “file name.h”
This directive treats has included in the current file i.e in current file also contain data of the file which has included by #include directive.
e.g
first create a file of file name cube.h which contain :

int cube ( int a)
{
Int b;
B=(a)*(a)*(a);
Return b;
}

Now create any another c file let math.c which contain :

#include “cube.h”
void main()
{
int p=5,q;
q=cube(p);
printf(“%d”,q);
}

Output :125
Explanation:

When we write #include “cube.h” the compile includes the contain of file cube.h i.e cube function in the math.c file.So we can use the function which has defined in cube.h .We can see the intermediate file of math.c :

#include : Search the file only include directory (c:\tc\include )
#include “filename” : Search the file include directory as well as current working directory.
Note : In the above question if you will save the file cube.h at c:\tc\include directory then you can write in math.c :
#include

#,##

(5) What is use of # and ## operator in c program ?
Ans:

There are two operator in preprocessor.
1. # this operator is called stringizing operator which convert any argument in the macro function in the string. So we can say pound sign # is string maker.
e.g
#define string(s) #s
void main()
{
char str[15]=string(World is our ) ;
printf(“%s”,str);
}
Output: World is our
Explanation : Its intermediate file is :


Argument of string macro function ‘World is our’ is converted into string by the operator # .Now the string constant “World is our” is replaced the macro call function in line number 4.
2. ##

This operator is called token pasting operator. When we use a macro function with various argument then we can merge the argument with the help of ## operator.
e.g
#define merge(p,q,r) p##q##r
Void main()
{
int merge(a,b,c)=45;
printf(“%d”,abc);
}
Output : 45
Explanation :
Arguments a,b,c in merge macro call function is merged in abc by ## operator .So in the intermediate file declaration statement is converted as :
int abc=45;