1. FUNCTIONS AND POINTERS
UNIT - 5
FUNCTIONS AND POINTERS

2. FUNCTION
Functions is a sub-program that contains one or more statements and it performs some task when called.

3. Types
Functions
Pre-Defined
Functions
User-Defined
Functions

4. Pre-Defined Functions
The pre-defined functions or library functions are built-in functions.
The user can use the functions, but cannot modify the function.
Example: sqrt()

5. User-Defined Functions
The functions defined by the user for their requirement are called user-defined functions.
Whenever it is needed, The user can modify the function.
Example: sum(a,b)

6. Advantage of User-Defined Functions
The length of the source program can be reduced.
It is easy to locate error.
It avoid coding of repeated instructions.

7. Elements of User-Defined Function
Function declaration
Function definition
Function call

8. Function Syntax datatype function_name (parameters list) {
local variable declaration;
…………………………
body of the function;
return(expression); }

9. How Function Works
Once a function is called the control passes to the called function.
The working of calling function is temporarily stopped.
When the execution of called function is completed then the control return back to the calling function and execute the next statement.

11. Parameters Actual Parameter
These are the parameters transferred from the calling function to the called function.
Formal Parameter
These are the parameters which is used in the called function.

13. return Statement
The return statement may or may not send some values to the calling function.
Syntax:
return; (or)
return(expression);

14. Function Prototypes Function with no arguments and no return values.
Function with arguments and no return values.
Function with arguments and return values.
Function with no arguments and with return values.

15. Function with no arguments and no return values
Here no data transfer take place between the calling function and the called function.
These functions act independently, i.e. they get input and display output in the same block.

17. Example #include <stdio.h> #include<conio.h>
void main() //calling function {
void add();
add(); }
void add() //called function
int a,b,c;
printf("\nEnter two number:");
scanf("%d%d",&a,&b);
c=a+b;
printf("\nSum is:%d",c);

18. Output
Enter two number:3 4
Sum is:7

19. Function with arguments and no return values
Here data transfer take place between the calling function and the called function.
It is a one way data communication, i.e. the called program receives data from calling program but it does not return any value to the calling program.

21. Example #include <stdio.h> #include<conio.h> void main() {
int a,b;
void add(int,int);
printf("\nEnter two number:");
scanf("%d%d",&a,&b);
add(a,b); }
void add(int x,int y) //function with arguments
int z;
z=x+y;
printf("\nSum is:%d",z);

22. Output
Enter two number:2 4
Sum is:6

23. Example #include <stdio.h> #include<conio.h> void main() {
int a,b;
void add(int a,int b);
printf("\nEnter two number:");
scanf("%d%d",&a,&b);
add(a,b); }
void add(int x,int y) //function with arguments
int z;
z=x+y;
printf("\nSum is:%d",z);

24. Output
Enter two number:2 4
Sum is:6

25. Function with arguments and return values
Here data transfer take place between the calling function and the called function as well as between called function and calling function .
It is a two way data communication, i.e. the called program receives data from calling program and it return some value to the calling program.

27. Example #include <stdio.h> #include<conio.h> void main() {
int a,b,c;
int add(int,int);
printf("\nEnter two number:");
scanf("%d%d",&a,&b);
c=add(a,b);
printf("\nSum is:%d",c); }
int add(int x,int y)
int z;
z=x+y;
return(z);

28. Output
Enter two number:6 7
Sum is:13

29. Function with no arguments and with return values
Here data transfer take place between the called function and the calling function.
It is a one way data communication, i.e. the called program does not receives data from calling program but it return some value to the calling program.

31. #include <stdio. h> #include<conio
#include <stdio.h> #include<conio.h> void main() { int add(),d; d=add(); printf("\nSum is:%d",d); } int add() //function wit no argument { int a,b,c; printf("\nEnter two number:"); scanf("%d%d",&a,&b); c=a+b; return(c);

32. Output
Enter two number:5 8
Sum is:13

33. Parameter Passing Methods
Call by value
Call by reference

34. Call by value Actual argument passed to the formal argument.
Any changes to the formal argument does not affect the actual argument.

35. Example #include <stdio.h> #include<conio.h> void main() {
int x,y,change(int,int);
printf("\nEnter value of x:");
scanf("%d",&x);
printf("\nEnter value of y:");
scanf("%d",&y);

36. change(x,y);
printf("\n\nValues in the Main()-->x=%d,y=%d",x,y); }
int change(int a,int b) {
int c;
c=a;
a=b;
b=c;
printf("\nValues in the Fuction -->x=%d,y=%d",a,b);

37. Output Enter value of x:5 Enter value of y:6
Values in the Fuction -->x=6,y=5
Values in the Main()-->x=5,y=6

38. Call by reference
Instead of passing value, the address of the argument will be passed.
Any changes to the formal argument will affect the actual argument.

39. Example #include <stdio.h> #include<conio.h> void main() {
int x,y;
int change(int*,int*);
printf("\nEnter value of x:");
scanf("%d",&x);
printf("\nEnter value of y:");
scanf("%d",&y);

40. change(&x,&y);
printf("\n\nValues in the Main()-->x=%d,y=%d",x,y); }
int change(int *a,int *b) {
int c;
c=*a;
*a=*b;
*b=c;
printf("\nValues in the Function -->x=%d,y=%d",*a,*b);

41. Output Enter value of x:5 Enter value of y:6
Values in the Function -->x=6,y=5
Values in the Main()-->x=6,y=5

42. Recursion
It is a process of calling the same function itself again and again until some condition is satisfied.
Syntax:
func1() {
………..
func1(); }

43. Example #include<stdio.h> #include<conio.h> void main() {
int a;
int rec(int);
printf("\nEnter the number:");
scanf("%d",&a);
printf("The factorial of %d! is %d",a,rec(a)); }

44. int rec(int x) {
int f;
if(x==1)
return(1);
else
f=x*rec(x-1);
return(f); }
Output:
Enter the number:5
The factorial of 5! is 120

45. Example: Working of 3!

46. Tower of Honoi 3 3 2 3 2 1 3 2 1 3

47. Tower of Honoi 3 3 2 3 2 1 3 2 1 3

48. #include<stdio. h> #include<conio
#include<stdio.h> #include<conio.h> void TOH(int n,char x,char y,char z); void main() { int n; printf("\nEnter number of plates:"); scanf("%d",&n); TOH(n,'A','B','C'); getch(); }

49. void TOH(int n,char x,char y,char z) { if(n>0) { TOH(n-1,x,z,y); // Recursive call 1 printf("\n%c -> %c",x,y); TOH(n-1,z,y,x); // Recursive call 2 }

50. Library Function It is pre-defined function.
The library function provides functions like mathematical, string manipulation etc,.

51. Example sqrt(x): It is used to find the square root of x
Example: sqrt(36) is 6
abs(x):
It is used to find the absolute value of x
Example: abs(-36) is 36
pow(x,y):
It is used to find the value of xy
Example: pow(5,2) is 25
ceil(x):
It is used to find the smallest integer greater than or equal to x
Example: ceil(7.7) is 8

52. rand():
It is used to generate a random number.
sin(x):
It is used to find the sine value of x
Example: sin(30) is 0.5
cos(x):
It is used to find the cosine value of x
Example: cos(30) is 0.86
tan(x):
It is used to find the tan value of x
Example: tan(30) is 0.577

53. toascii(x):
It is used to find the ASCII value of x
Example: toascii(a) is 97
toupper(x):
It is used to convert lowercase character to uppercase.
Example: toupper(‘a’) is A
toupper(97) is A
tolower(x):
It is used to convert uppercase character to lowercase.
Example: tolower(‘A’) is a

54. Example: #include<stdio.h> #include<conio.h>
#include<math.h>
#include<ctype.h>
void main() {
int x,y=2;
printf("\nEnter the number:");
scanf("%d",&x);
printf("\nThe squareroot of %d is %f",x,sqrt(x));
printf("\nThe value of %d power%dis%f ",x,y,pow(6,2));

55. printf("\nThe ceiling of 6.7 is %f",ceil(6.7));
printf("\nThe floor of 6.7 is %f",floor(6.7));
printf("\nThe absolute value of -6 is %d",abs(-6));
printf("\nThe value of sin 45 is %f",sin(45));
printf("\nThe uppercase of 'a' is %c",toupper('a'));
printf("\nThe uppercase of 97 is %c",toupper(97));
getch(); }

56. Output: Enter the number:6 The squareroot of 6 is 2.449490
The value of 6 power 2 is
The ceiling of 6.7 is
The floor of 6.7 is
The absolute value of -6 is 6
The value of sin 45 is
The uppercase of 'a' is A
The uppercase of 97 is A

57. Array
An Array is a collection of similar data items, that are stored under a common name.
Types
One-Dimensional array
Two-Dimensional array
Multi-Dimensional array

58. One-Dimensional array Array Declaration
Syntax:
data_type array_name[size];
Example: int x[3]; x
X[0]
X[1]
X[2]

59. Array initialization
At compile time
At run time

60. At compile time x Syntax: data_type array_name[size]={variables};
Example: int x[3]={5,3,7}; x 5 3 7
X[0]
X[1]
X[2]

61. At Run time Array can also initialize at the run time. Example:
while(i<10) {
if(i<5)
sum[i]=0;
else
sum[i]=sum[i]+i; }

62. Example:
scanf(“%d%d”,&a[0],&a[1]);

63. Example #include<stdio.h> #include<conio.h> void main() {
int x[2],i;
printf("\nEnter the inputs:");
for(i=0;i<2;i++)
scanf("%d",&x[i]);
printf("\nThe value in x[%d] is %d",i,x[i]);
getch(); }

64. Output Enter the inputs:3 6 The value in x[0] is 3

65. Example #include<stdio.h> #include<conio.h> void main() {
int i;
char x[5]={'a','b','c','d','e'};
clrscr();
for(i=0;i<5;i++)
printf("\nThe value in x[%d] is %c",i,x[i]);
getch(); }

66. Output The value in x[0] is a The value in x[1] is b
The value in x[2] is c
The value in x[3] is d
The value in x[4] is e

67. Two-Dimensional array Array Declaration
Syntax:
data_type array_name[row_size] [col_size];
Example: int x[3][2];
Col 0 Col 1
row 0
row 1
row 2
X[0][0]
X[1][0]
X[2][0]
X[0][1]
X[1][1]
X[2][1]

68. Array Initialization Syntax:
data_type array_name[row_size] [col_size];={variables};
Example: int x[2][2]={1,50,2,75};

69. int x[2][2]={ {1,50},
{2,75} };
(or)
int x[ ][2]={ {1,50},

70. Col 0 Col 1
row 0
row 1 1 50 2 75

71. Example #include<stdio.h> #include<conio.h> void main() {
int i,j;
int x[2][2]={ {1,50},
{2,75} };
clrscr();
for(i=0;i<2;i++)
for(j=0;j<2;j++)
printf("\nThe value in x[%d][%d] is %d",i,j,x[i][j]);
getch(); }

72. Output The value in x[0][0] is 1 The value in x[0][1] is 50

73. Example #include<stdio.h> #include<conio.h> void main() {
int i,j;
int x[][2]={ {1,50},{2,75},{3,65}};
clrscr();
for(i=0;i<=2;i++)
for(j=0;j<2;j++)
printf("\nThe value in x[%d][%d] is %d",i,j,x[i][j]);
getch(); }

74. Output The value in x[0][0] is 1 The value in x[0][1] is 50

75. Matrix Addition #include<stdio.h> #include<conio.h>
void main() {
int i,j,k,r1,r2,c1,c2;
int a[5][5],b[5][5],c[5][5];
clrscr();
step1:
printf("\n Enter the size of matrix A:");
scanf("%d%d",&r1,&c1);
printf("\n Enter the size of matrix B: ");
scanf("%d%d",&r2,&c2);
if((c1==c2)&&(r1==r2))
goto step2;
else
goto step1;

76. step2:
printf("\n Enter the elements of matrix A \n");
for(i=0;i<r1;i++) {
for(j=0;j<c1;j++)
scanf("%d",&a[i][j]); }
printf("\n Enter the elements of matrix B \n");
for(i=0;i<r2;i++)
for(j=0;j<c2;j++)
scanf("\t%d",&b[i][j]);

77. for(i=0;i<r1;i++) {
for(j=0;j<c1;j++)
c[i][j]=0;
c[i][j]=c[i][j]+a[i][j]+b[i][j]; }
printf("\n The resultant matrix after addition of A & B is\n");
printf("%d\t",c[i][j]);
printf("\n");
getch();

78. Output Enter the size of matrix A: 2 2 Enter the size of matrix B: 2
Enter the elements of matrix A
Enter the elements of matrix B 3
The resultant matrix after addition of A&B is

79. Matrix Multiplication
#include<stdio.h>
#include<conio.h>
void main() {
int i,j,k,r1,r2,c1,c2;
int a[5][5],b[5][5],c[5][5];
clrscr();
step1:
printf("\n Enter the size of matrix A \n");
scanf("%d%d",&r1,&c1);
printf("\n Enter the size of matrix B \n");
scanf("%d%d",&r2,&c2);
if(c1==r2)
goto step2;
else
goto step1;

80. step2:
printf("\n Enter the elements of matrix A \n");
for(i=0;i<r1;i++) {
for(j=0;j<c1;j++)
scanf("%d",&a[i][j]); }
printf("\n Enter the elements of matrix B \n");
for(i=0;i<r2;i++)
for(j=0;j<c2;j++)
scanf("\t%d",&b[i][j]);

81. for(i=0;i<r1;i++) {
for(j=0;j<c2;j++)
c[i][j]=0;
for(k=0;k<c1;k++)
c[i][j]=c[i][j]+a[i][k]*b[k][j]; }
printf("%d\t",c[i][j]);
printf("\n");
getch();

82. Output 2 Enter the size of matrix B:2 Enter the elements of matrix A 4
Enter the size of matrix A:2 2
Enter the size of matrix B:2
Enter the elements of matrix A 4
Enter the elements of matrix B
The resultant matrix is

83. Enter the size of matrix A:23
Enter the size of matrix B:3 2
Enter the elements of matrix A 1 4 5 6
Enter the elements of matrix B 8

85. Passing array to Function
Here an array is transferred as parameter to a function.
void main() void fun(n,b[])
{ {
void fun(int,int); int x,b[5];
int a[5],n; …………..
…………… …………..
fun(n,a);
…………… } }

86. Example #include<stdio.h> #include<conio.h>
void add(int,int b[]);
void main() {
int a[5],i,n;
clrscr();
printf("\n Enter the Number: ");
scanf("%d",&n);
printf("\n Enter the Values: ");
for(i=0;i<n;i++)
scanf("%d",&a[i]);
add(n,a); }

87. void add(int x,int b[]) {
int sum=0,i;
for(i=0;i<x;i++)
sum=sum+b[i];
printf("\nThe sum is: %d",sum); }

88. Output
Enter the Number: 5
Enter the Values: 1 2 3 4 5
The sum is: 15

89. Array of Characters
In array the characters are terminated by the null (‘\0’) character.
Example: char a[]={a,b,c}; a b c \0

90. Example #include<stdio.h> #include<conio.h> void main() {
int i=0;
char a[]="abcd";
clrscr();
while(a[i]!='\0')
printf("\t%c",a[i]);
i++; }

91. Output
a b c d

92. Multi Dimensional Array
Syntax
datatype array_name [size1][size2]….[size n]
datatype - type of the data.
array_name -name of the array.
size -size of the array.

93. Example: int a[3][3][3]; Col 0 Col 1 Col 2 row 0 row 1 row 2 X[0][0]

94. String Functions strlen() It is used to find the length of the string.
syntax:
strlen(string)
strcpy()
It is used to copy one string to another.
strcpy(string1,string2)
strcat()
It is used to combine two strings.
strcat(string1,string2)

95. strcmp()
It is used to compare two strings.
syntax:
strcmp(string1,string2)
Returns 0 if two strings are equal.
Return value <0 if s1 is less than s2.
Return value >0 if s1 is greater than s2.
strrev()
It used to reverse a string.
strrev(string)
strlwr(), strupr()
It used to change the case of a string.
strlwr(string)
strupr(string)

96. strncpy()
It used to copy ‘n’ characters of one string to another.
strstr()
It is used to determine the first occurrence of a given string in another string.
strncat()
It Appends source string to destination string upto specified length.
strspn()
It is used t find upto what length two strings are identical.

97. strncmp() strcmpi() strnicmp() strchr() strrchr()
It is used to compare ‘n’ character of two strings.
strcmpi()
It is used to compare two strings without regarding the case.
strnicmp()
It is used to compare first ‘n’ characters of two strings without regarding the case.
strchr()
It is used to determine the first occurrence of a given character in a string.
strrchr()
It is used to determine the last occurrence of a given character in a string.

98. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="college";
int b;
clrscr();
b=strlen(a);
printf("\nThe length of the string is %d",b);
getch(); }
Output:
The length of the string is 7

99. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="IT";
char b[]="Dept";
clrscr();
strcpy(a,b);
printf("\nThe string is %s",a);
getch(); }
Output:
The string is Dept

100. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="IT";
char b[]="Dept";
clrscr();
strcat(a,b);
printf("\nThe string is %s",a);
getch(); }
Output:
The string is ITDept

101. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="itdept";
char b[]="it";
int i;
clrscr();
i=strcmp(a,b);
if(i==0)
printf("\nstrings are equal:%d",i);
else if(i<0)
printf("\nstring1 is less than string2:%d",i);

102. else
printf("\nstring1 is greater than string2:%d",i);
getch(); }
Output:
string1 is greater than string2:100

103. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="itdept";
clrscr();
printf("\nThe string is :%s",a);
strupr(a);
printf("\nThe string after conversion to uppercase :%s",a);
strlwr(a);
printf("\nThe string after conversion to lowercase :%s",a);
getch(); }

104. Output The string is :itdept
The string after conversion to uppercase :ITDEPT
The string after conversion to lowercase :itdept

105. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="Dept";
clrscr();
printf("\nThe string is %s",strrev(a));
getch(); }
Output:
The string is tpeD

106. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="itdept";
char b[15];
int i=0;
clrscr();
strncpy(b,a,2);
b[2]='\0';
printf("\nThe string is :%s",b);
getch(); }

107. Output:
The string is :it

108. String Palindrome #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
int len,i,j;
char str[15];
clrscr();
printf("\n Enter the string:");
scanf("%s",str);
len=strlen(str);

109. for(i=0,j=len-1;i<len/2;i++,j--){
if(str[i]!=str[j])
printf("\nThe String is not a palindrome");
getch();
exit(0); }
printf("\nThe String is a palindrome");
Output:
Enter the string:abcba
The String is a palindrome

110. Enumerated Data Type It is user defined data type.
The user can create their own data type and define some values to the variables.
Syntax:
enum tag_name {
enum1;
enum2;
………. };

111. Example #include <conio.h> #include <stdio.h> void main(){
enum week {sun,mon,tue,wed,thr,fri,sat};
clrscr();
printf("\nMonday=%d",mon);
printf("\nSaturday=%d",sat);
getch(); }
Output:
Monday=1
Saturday=6

112. Example #include <conio.h> #include <stdio.h> void main(){
enum week {sun=10,mon,tue,wed,thr,fri,sat};
clrscr();
printf("\nMonday=%d",mon);
printf("\nsaturday=%d",sat);
getch(); }
Output:
Monday=11
saturday=16

113. Structure
A Structure is a collection of different data items, that are stored under a common name.
Syntax:
struct structure_name {
structure element1;
structure element2;
……………………. };

114. Example:
struct stud {
int sno;
char name[10];
int mark; };
struct stud s;

115. Example #include<stdio.h> #include<conio.h> struct stud {
int regno;
char name[10];
int m1;
int m2;
int m3; };
struct stud s;
void main()
float tot,avg;

116. printf("\nEnter the student regno,name,m1,m2,m3:"); scanf("%d%s%d%d%d",&s.regno,&s.name,&s.m1,&s.m2,&s.m3);
tot=s.m1+s.m2+s.m3;
avg=tot/3;
printf("\nThe student Details are:");
printf("\n%d\t%s\t%f\t%f",s.regno,s.name,tot,avg); }

117. Output Enter the student regno,name,m1,m2,m3:100 aaa 87 98 78
The student Details are:
aaa

118. Structure assignment
It is possible to assign one structure information to another structure of same type using simple assignment statement.

119. Example #include<stdio.h> #include<conio.h> void main() {
struct
int a;
}x,y;
clrscr();
x.a=10;
y=x;
printf("The value of y.a is%d",y.a);
getch(); }

120. Output
The value of y.a is10

121. Example #include<stdio.h> #include<conio.h> struct stud {
int regno;
char name[10],grade;
int m1,m2,m3;
float avg,tot;
} s[10];
void main()
int i,n;
printf("\nEnter the no.of students:");
scanf("%d",&n);

122. for(i=0;i<n;i++) {
printf("\nEnter the student regno,name,m1,m2,m3:");
scanf("%d%s%d%d%d",&s[i].regno,&s[i].name,&s[i].m1,
&s[i].m2,&s[i].m3);
s[i].tot=s[i].m1+s[i].m2+s[i].m3;
s[i].avg=s[i].tot/3;
if(s[i].m1<35||s[i].m2<35||s[i].m3<35)
s[i].grade='f';
else
if(s[i].avg>=75)
s[i].grade='d';
else if(s[i].avg>=60)

123. s[i].grade='A';
else if(s[i].avg>=50)
s[i].grade='B';
else if(s[i].avg>=35)
s[i].grade='C'; }
printf("\nSTUDENT MARK LIST\n");
printf("\nREGNO\tNAME\tTOTAL\tAvg\tGRADE");
for(i=0;i<n;i++)
printf("\n%d\t%s\t%f\t%f\t%c",s[i].regno,s[i].name,s[i].tot,s[i].avg,s[i].grade);
getch();

124. Enter the no.of students:2
Enter the student regno,name,m1,m2,m3:101
aaa 89 98 78
Enter the student regno,name,m1,m2,m3:102
bbb 59 68 76
STUDENT MARK LIST
REGNO NAME TOTAL Avg GRADE
aaa d
bbb A

125. Union
An Union is a collection of different data items, that are stored under a common name. Here same memory is shared by its members.
Syntax:
union union _name {
union element1;
union element2;
………………… };

126. Example:
union result {
int mark;
float avg;
char grade; };
union result s;

127. Example #include<stdio.h> #include<conio.h> union stud {
int a;
char b[2]; };
void main()
union stud c;

128. c.a=256;
printf("\nc.a value is%d",c.a);
printf("\nc.b[0] value is%d",c.b[0]);
printf("\nc.b[1] value is%d",c.b[1]); }
Output:
c.a value is256
c.b[0] value is0
c.b[1] value is1

129. 256 = 00000010 00000000 c.a - 2 Byte c.b[0] 1 Byte c.b[0] 1 Byte
Higher bit Lower bit
c.b[0]
c.b[1]

130. Example #include<stdio.h> #include<conio.h> struct student{
int a;
int b;
char c;
}s;
union student1
}s1;

131. void main() {
printf("\nThe size of struct is %d",sizeof(s));
printf("\nThe size of union is %d",sizeof(s1));
getch(); }
Output:
The size of struct is 5
The size of union is 2

132. Structure & Union int int char int ,int, char 2 Byte 2Byte 1Byte

133. Preprocessor
It is a program that processes the source program before compilation.
It operates under the following directives
File Inclusion
Macro substitution
Conditional inclusion

134. File Inclusion
It is used to include some file that contains functions or some definitions.
Syntax:
#include<filename> (or)
#include“filename”
Eg: #include<stdio.h>
#include “ex.c”

135. Example #include<stdio.h> #include<conio.h>
#include "addition.txt"
void main() {
int a,b;
printf("\nEnter the numbers:");
scanf("%d%d",&a,&b);
printf("The Value is %d",add(a,b));
getch(); }

136. addition.txt
int add(int a,int b) {
return(a+b); }

137. Output
Enter the numbers:7 4
The Value is 11

138. Example #include<stdio.h> #include<conio.h>
#include "fact.c"
void main() {
int a;
printf("\nEnter the number:");
scanf("%d",&a);
printf("The factorial of %d! is %d",a,rec(a));
getch(); }

139. fact.c int rec(int x) { int f; if(x==1) return(1); else f=x*rec(x-1);
return(f); }

140. Output
Enter the number:5
The factorial of 5! is 120

141. Macro Substitution
It is used to define and use integer, string, or identifier in the source program
The three forms of macros are
Simple Macro
Argumented Macro
Nested Macro

142. Simple Macro It is used to define some constants Syntax
# define identifier string/integer
Eg:
#define pi 3.14
#define CITY “chennai”

143. Example #include<stdio.h> #include<conio.h>
#define pi 3.14
#define CITY "chennai"
void main() {
printf("The Value is %f",2*pi);
printf("\nThe Value CITY is %s",CITY);
getch(); }
Output:
The Value is
The Value CITY is chennai

144. Argumented Macro
It is used to define some complex forms in the source program.
Syntax:
#define identifier (v1,v2,….) string/integer
Eg:
#define cube(n) (n*n*n)

145. Example #include<stdio.h> #include<conio.h>
#define cube(n) (n*n*n)
void main() {
printf("The Value of 3 cube is %d",cube(3));
getch(); }
Output:
The Value of 3 cube is 27

146. Nested Macro Here one macro is used by another macro. Eg: #define a 3
#define sq a*a

147. Example #include<stdio.h> #include<conio.h> #define a 3
#define sq a*a
void main() {
printf("The Value is %d",sq);
getch(); }
Output:
The Value is 9

148. Conditional Inclusion
It is used to include some conditional statements.

149. Example #include<stdio.h> #include<conio.h> #define a 3
#ifdef a
#define c a+5
#endif
void main() {
printf("\nThe value C is %d",c);
getch(); }
Output:
The value C is 8

150. Pointers
Pointer is a variable that contains the memory address of another variable.

151. Example:
x=5
x Variable
Address 5
Value

152. Example #include<stdio.h> #include<conio.h> void main() {
int x=5;
printf("\n The Address of x = %u",&x);
printf("\n The Value of x = %d",x); }
Output
The Address of x = 8714
The Value of x = 5

153. Pointer Declaration Syntax data-type *pointer-name;
data-type - Type of the data to which the pointer points.
pointer-name - Name of the pointer
Example: int *a;

154. Accessing Variable through Pointer
If a pointer is declared and assigned to a variable, then the variable can be accessed through the pointer.
Example:
int *a;
x=5;
a=&x;

155. Example #include<stdio.h> #include<conio.h> void main() {
int x=5;
int *a;
a=&x;
printf("\n The Value of x = %d",x);
printf("\n The Address of x = %u",&x);
printf("\n The Value of a = %d",a);
printf("\n The Value of x = %d",*a); }

156. Output The Value of x = 5 The Address of x = 8758
The Value of a = 8758

157. Example: #include<stdio.h> #include<conio.h> void main() {
int y=10;
int *a;
a=&y;
printf("\n The Value of y = %d",y);
printf("\n The Address of y = %u",&y);
printf("\n The Value of a = %d",a);
printf("\n The Address of a = %u",&a); }

158. a y
Variable
Value
Address
5001 10
8000
5001

159. Output The Value of y = 10 The Address of y = 5001
The Value of a = 5001
The Address of a = 8000

160. Null Pointer
A pointer is said to be null pointer if zero is assigned to the pointer.
Example
int *a,*b;
a=b=0;

161. Pointer to Pointer
Here one pointer stores the address of another pointer variable.
Example:
int x=10,*a,**b;
a=&x;
b=&a;

162. b a x
Variable
Value
Address
8000
5001 10
9000
8000
5001

163. Example
#include<stdio.h>
#include<conio.h>
void main() {
int a=10;
int *b,**c;
b=&a;
c=&b;
printf("\n The Value of a = %d",a);
printf("\n The Address of a = %u",&a);
printf("\n The Value of b = %d",b);
printf("\n The Address of b = %u",&b);
printf("\n The Value of c = %d",c);
printf("\n The Address of c = %u",&c); }

164. Output The Value of a = 10 The Address of a = 5001
The Value of b = 5001
The Address of b = 8000
The Value of c = 8000
The Address of c = 9000

165. Pointers and Functions
Call by Value
Call by Reference

166. Call by value Actual argument passed to the formal argument.
Any changes to the formal argument does not affect the actual argument.

167. Example #include <stdio.h> #include<conio.h> void main() {
int x,y,swap(int,int);
printf("\nEnter value of x:");
scanf("%d",&x);
printf("\nEnter value of y:");
scanf("%d",&y);

168. change(x,y);
printf("\n\nValues in the Main()-->x=%d,y=%d",x,y); }
int swap(int a,int b) {
int c;
c=a;
a=b;
b=c;
printf("\nValues in the Function -->x=%d,y=%d",a,b);

169. Output Enter value of x:5 Enter value of y:6
Values in the Function -->x=6,y=5
Values in the Main()-->x=5,y=6

171. Call by reference
Instead of passing value, the address of the argument will be passed.
Any changes to the formal argument will affect the actual argument.

172. Example #include <stdio.h> #include<conio.h> void main() {
int x,y,change(int*,int*);
printf("\nEnter value of x:");
scanf("%d",&x);
printf("\nEnter value of y:");
scanf("%d",&y);

173. change(&x,&y);
printf("\n\nValues in the Main()-->x=%d,y=%d",x,y); }
int change(int *a,int *b) {
int c;
c=*a;
*a=*b;
*b=c;
printf("\nValues in the Function -->x=%d,y=%d",*a,*b);

174. Output Enter value of x:5 Enter value of y:6
Values in the Function -->x=6,y=5
Values in the Main()-->x=6,y=5

175. Pointer to Array
The elements of the array can also be accessed through a pointer.
Example
int a[3]={2,3,7};
int *b;
b=a;

176. Example:
#include<stdio.h>
#include<conio.h>
void main() {
int a[3]={2,3,7};
int *b;
b=a;
printf("\n The Value of a[0] = %d",a[0]);
printf("\n The Address of a[0] = %u",&a[0]);
printf("\n The Value of b = %d",b); }

177. b
a[0]
Variable
Value
Address
8744 2
9000
8744

178. Output The Value of a[0] = 2 The Address of a[0] = 8744
The Value of b = 8744

179. Example #include<stdio.h> #include<conio.h> void main() {
int a[5]={2,3,7,9,10};
int i;
for(i=0;i<5;i++)
printf("\n The Value of a[%d] = %d",i,a[i]);
printf("\n The Address of a[%d] = %u",i,&a[i]); }

180. Array Value Address 2 3 7 9 10 a[0] a[1] a[2] a[3] a[4]

181. Output The Value of a[0] = 2 The Address of a[0] = 8724

182. Example #include<stdio.h> #include<conio.h> void main() {
int a[5]={1,2,3,4,5};
int i,sum=0;
int *b;
b=a;
for(i=0;i<5;i++)
sum=sum + *b;
b++; //b=b+1 }
printf("\n The Sum is %d",sum);

183. Output
The Sum is 15

184. Pointer and Structures
Syntax:
struct structure_name {
structure element1;
structure element2;
…………………….
}variable,*ptr;

185. Example:
struct stud {
int sno;
char name[10];
int mark; };
struct stud *s;

186. Example #include<stdio.h> #include<conio.h> struct stud {
int regno;
char name[10];
int m1;
int m2;
int m3; };
struct stud s;
struct stud *t;

187. void main() {
float tot,avg;
t=&s;
printf("\nEnter the student regno,name,m1,m2,m3:");
scanf("%d%s%d%d%d",&s.regno,&s.name,&s.m1,&s.m2,&s.m3);
tot=s.m1+s.m2+s.m3;
avg=tot/3;
printf("\nThe student Details are:");
printf("\n%d\t%s\t%f\t%f",s.regno,s.name,tot,avg);
printf("\n%d\t%s\t%f\t%f",t->regno,t->name,tot,avg); }

188. Output Enter the student regno,name,m1,m2,m3:1 aaa 76 89
The student Details are:
aaa

189. Command Line Argument
It allows the user to pass some information to the program while running the program.

190. Example #include<stdio.h> #include<conio.h>
void main(int argc,char argv[]) {
printf("\n The Argument is %s",argv[0]);
getch(); }

191. Output
C:\tc>a
The Argument is C:\TC\A.EXE

192. String Palindrome #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char s1[15],s2[15];
printf("\nenter the string:");
scanf("%s",s1);
strcpy(s2,s1);
strrev(s1);

193. The string is palindrome
if(strcmp(s1,s2)==0)
printf("\n The string is palindrome");
else
printf("\n The string is not a palindrome");
getch(); }
Output:
enter the string: aba
The string is palindrome

194. Developing a ‘C’ Program
The Program development life cycle is considered as a sequence of events by the programmer to develop the program.
The Program development life cycle contains the following phase
Program Design
Program Coding
Program Testing

195. Program Design Analysing the problem Algorithm development
Selection of conditional and control structure etc,.

196. Program Coding Documentation Statement construction
Input and output format etc,.

197. Program Testing
It is the process of executing the program with sample data

199. Example #include<stdio.h> #include<conio.h> #define p 3.14
void main() {
#ifdef p
printf("\nPentium");
#else
printf("\n Celeron");
#endif
printf("\nthe value is %f",2*p);
getch(); }
Output:
Pentium
the value is

201. Example #include<stdio.h> #include<conio.h> struct stud {
int regno;
char name[10];
int m1;
int m2;
int m3; };
struct stud s;
void main()
float tot,avg;
int i;

202. printf("\nEnter the student regno,name,m1,m2,m3:");
for(i=0;i<2;i++) {
scanf("%d%s%d%d%d",&s.regno,&s.name,&s.m1,&s.m2,&s.m3);
tot=s.m1+s.m2+s.m3;
avg=tot/3; }
printf("%d\t%s\t%f\t%f",s.regno,s.name,tot,avg);

203. Enter the student regno,name,m1,m2,m3:100
aaa 78 67 98
101
bbb 80 90 75
bbb
101bbb

204. #include <string.h>
#include <stdio.h>
int main(void) {
char string[15];
char *ptr, c = 'r';
strcpy(string, "This is a string");
ptr = strchr(string, c);
if (ptr)
printf("The character %c is at position: %d\n", c, ptr-string);
else
printf("The character was not found\n");
return 0; }

205. Example #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
char a[]="Dept";
int i=0;
clrscr();
while(a[i]!='\0')
printf("\nThe character is %c",a[i]);
i++; }
getch();

206. The character is D
The character is e
The character is p
The character is t

208. Structure

212. Lab Exercise
C Programs

213. Function-with arg & return
#include <stdio.h>
#include<conio.h>
void main() {
int a,b,c;
int add(int,int);
printf("\nEnter two number:");
scanf("%d%d",&a,&b);
c=add(a,b);
printf("\nSum is:%d",c); }
int add(int x,int y)
int z;
z=x+y;
return(z);

214. Output
Enter two number:6 7
Sum is:13

215. Example #include <stdio.h> #include<conio.h> void main() {
int x,y,change(int*,int*);
printf("\nEnter value of x:");
scanf("%d",&x);
printf("\nEnter value of y:");
scanf("%d",&y);

216. change(&x,&y);
printf("\n\nValues in the Main()-->x=%d,y=%d",x,y); }
int change(int *a,int *b) {
int c;
c=*a;
*a=*b;
*b=c;
printf("\nValues in the Function -->x=%d,y=%d",*a,*b);

217. Output Enter value of x:5 Enter value of y:6
Values in the Function -->x=6,y=5
Values in the Main()-->x=6,y=5

218. Factorial-Recursive Fn
#include<stdio.h>
#include<conio.h>
void main() {
int a;
int rec(int);
printf("\nEnter the number:");
scanf("%d",&a);
printf("The factorial of %d! is %d",a,rec(a)); }

219. int rec(int x) {
int f;
if(x==1)
return(1);
else
f=x*rec(x-1);
return(f); }
Output:
Enter the number:5
The factorial of 5! is 120

220. Example: Working of 3!

221. Matrix Multiplication
#include<stdio.h>
#include<conio.h>
void main() {
int i,j,k,r1,r2,c1,c2;
int a[5][5],b[5][5],c[5][5];
clrscr();
step1:
printf("\n Enter the size of matrix A \n");
scanf("%d%d",&r1,&c1);
printf("\n Enter the size of matrix B \n");
scanf("%d%d",&r2,&c2);
if(c1==r2)
goto step2;
else
goto step1;

222. step2:
printf("\n Enter the elements of matrix A \n");
for(i=0;i<r1;i++) {
for(j=0;j<c1;j++)
scanf("%d",&a[i][j]); }
printf("\n Enter the elements of matrix B \n");
for(i=0;i<r2;i++)
for(j=0;j<c2;j++)
scanf("\t%d",&b[i][j]);

223. for(i=0;i<r1;i++) {
for(j=0;j<c2;j++)
c[i][j]=0;
for(k=0;k<c1;k++)
c[i][j]=c[i][j]+a[i][k]*b[k][j]; }
printf("%d\t",c[i][j]);
printf("\n");
getch();

224. Output 2 Enter the size of matrix B:2 Enter the elements of matrix A 4
Enter the size of matrix A:2 2
Enter the size of matrix B:2
Enter the elements of matrix A 4
Enter the elements of matrix B
The resultant matrix is

226. Lab Ex:9,Finding area, circumference of circle
#include<stdio.h>
#include <conio.h>
void main ( ) {
int r;
float area,c;
clrscr( );
printf(" \nEnter the value of r:");
scanf("%d",&r);

227. area=3.14*r*r;
c=2*3.14*r;
printf(" \nThe area is :%f",area);
printf(" \nThe circumference is :%f",c);
getch( ); }
Output:
Enter the value of r:7
The area is :
The circumference is :

228. Lab Ex:9,Conversion of Celsius to Fahrenheit
#include<stdio.h>
#include <conio.h>
void main ( ) {
float c,f;
clrscr( );
printf(" \nEnter the value of c:");
scanf("%f",&c);
f=(c*1.8)+32;
printf(" \nThe Fahrenheit is :%f",f);
getch( ); }

229. Enter the value of c:35
The fahrenheit is :

230. Lab Ex:11,Arithmetic operations
#include<stdio.h>
#include<conio.h>
void main() {
int a,b,c,d,e,f;
clrscr();
printf("\nEnter the values of A and B:");
scanf("%d%d",&a,&b);
c=a+b;
d=a-b;
e=a*b;
f=a/b;

231. printf("\nThe values of A + B:%d",c);
printf("\nThe values of A - B:%d",d);
printf("\nThe values of A * B:%d",e);
printf("\nThe values of A / B:%d",f);
getch(); }

232. Output Enter the values of A and B:6 3 The values of A + B:9

233. Lab.Ex13,Largest among 3 nos
#include<stdio.h>
#include <conio.h>
void main ( ) {
int a,b,c;
clrscr( );
printf(" \nEnter the value of a:");
scanf("%d",&a);
printf(" \nEnter the value of b:");
scanf("%d",&b);
printf(" \nEnter the value of c:");
scanf("%d",&c);

234. if((a>b)&&(a>c)){
printf(" \nA is Big"); }
else
if(b>c)
printf(" \nB is Big");
printf(" \nC is Big");
getch( );

235. Output Enter the value of a:5 Enter the value of b:7
Enter the value of c:3
B is Big

236. String Palindrome #include<stdio.h> #include<conio.h>
#include<string.h>
void main() {
int len,i,j;
char str[15];
clrscr();
printf("\n Enter the string:");
scanf("%s",str);
len=strlen(str);

237. for(i=0,j=len-1;i<len/2;i++,j--){
if(str[i]!=str[j])
printf("\nThe String is not a palindrome");
getch();
exit(0); }
printf("\nThe String is a palindrome");
Output:
Enter the string:abcba
The String is a palindrome

238. Lab.Ex:14,Quadratic Equation
#include<stdio.h>
#include <conio.h>
#include<math.h>
void main ( ) {
int a,b,c,d,r1,r2;
clrscr( );
printf(" \nEnter the value of a:");
scanf("%d",&a);
printf(" \nEnter the value of b:");
scanf("%d",&b);
printf(" \nEnter the value of c:");
scanf("%d",&c);
d=b*b-4*a*c;

239. if(d>=0) {
r1=(-b+sqrt(d))/(2*a);
r2=(-b-sqrt(d))/(2*a);
printf(" \nThe roots are %d,%d",r1,r2); }
else
printf(" \nThe roots are imaginary");
getch( );

240. Output Enter the value of a:1 Enter the value of b:4
Enter the value of c:4
The roots are -2,-2