U4.ppt

Unit IV
Strings and Functions
L.NIVETHA AP /CSE - KNCET

Strings – Character Arrays – Reading
String input – String Library Functions – List
of Strings – Command Line Arguments –
Functions: Types – Declaration – Definition –
Function Call – Pass by Value – Pass by
Reference – Passing arrays to functions –
Recursion – Pointer to function.

STRINGS and its Operations
Presented by,
L.Nivetha,AP/CSE,
KNCET
KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY
(AUTONOMOUS)
NAMAKKAL - TRICHY MAIN ROAD, THOTTIAM, TRICHY-621 215
L.NIVETHA AP/CSE,KNCET

Strings
strings are defined as sequence of character
enclosed with in double quotes.
every string literal constant is automatically
terminated by null character. ie : ‘0’.
string literal also store into memory like normal
variable.
Here additional one byte needed for storing null
character
Example:
“hai” h a i 0

The length of the string is calculated based on
the number character present in the string,
The null character not counted with in the
string length

Character array
Character variable can be store character
constant ex: char a=‘s’
if we store string constant we need to
declare the character variable as array. Ex:
char a[10]=“ram”
Syntax:
char identifier[size_specifier]=“string_literal”

To declare the string variable into character
array
To initialize the string constant into two ways:
1. By using string literal constant
Here we assign the string constant into
character array variable using double quotes
Ex:char a[10]=“RAM”;
2. By using initializing the list
Here to initialize the character array by using
list of character intilizer.
Ex: char a[10]={’r , ’a’ , ’m’ , ’0’};

Example:
#include<stdio.h>
#include<conio.h>
Void main()
{
char name[5]=“ram”;
char initial=‘s’;
printf(“%c.%s”, initial,name);
}
Output: s.ram

Reading string input:
 To read the string input by using scanf()
statement with %s control string.
Example:
#include<stdio.h>
void main()
{
char name[10];
printf("Enter the name ");
scanf("%s", &name);
printf("name is:%s", name);
}

STRING OPERATIONS
STRING HANDLING FUCTION’S:
1. strlen()
2. Strcmp()
3. strcpy()
4. Strncpy()
5. Strcat()
6. Strdup()
7. Strrev()
8. Strlwr()
9. Strupr()
10.Strpbrk() L.NIVETHA AP /CSE - KNCET

STRING HANDLING FUCTION’S
1. strlen() - It is a predefined function ,used to find the length
of the string. It will return integer output.
syntax:
variable=strlen(string);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name[30]=“sriram”;
int a;
clrscr();
a=strlen(name);
printf(“%d”,a);
} o/p: 6

Strcmp() function –
It is a predefined string function.
it is used to compare character of two strings ,
if any difference it provide how many
character to be differed , if no difference to
give 0 as output.
Syntax:
variable=strcmp(string1 , string2);

Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“sriram” , name2[30]= “balram”;
int a,b;
clrscr();
a=strcmp(name1, “sriram”);
b=strcmp(name1 , name2);
printf(“%d%d”, a,b);
}
o/p: 0 3

strcpy() function – it is a predefined string
function. used to copy the content of one
string to another.
syntax:
strcpy(string1,string2);
string1 – destination string
string2 - source string

Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“sriram” , name2[30];
clrscr();
strcpy(name2 , name1);
printf(“%s”, name2);
}
o/p:
sriram L.NIVETHA AP /CSE - KNCET

Strncpy() function – used to copy first n characters
from one string into another.
Syntax:
strncpy(string1 , string2 ,n);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“sriram” , name2[30];
clrscr();
strncpy(name2 , name1 , 3);
}
o/p:
sri L.NIVETHA AP /CSE - KNCET

Strcat() function – it is used to combine two strings ,it is also
called as string concatenation.
Syntax:
strcat(string1 , string2);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“sriram” , name2[30]= “Balram”;
clrscr();
strcat(name1 , name2);
}
o/p:
sriramBalram L.NIVETHA AP /CSE - KNCET

Strdup() function: It is used same as well as strcpy() , here it will create
a duplicate copy of source string .
Syntax:
strdup(string);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“sriram”;
clrscr();
char *name2=strdup(name1);
}
o/p: sriram

Strrev() function – it is a predefined string function, it is
used to reverse the given string .
Syntax:
strrev(string);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“sriram”;
clrscr();
strrev(name1);
}
o/p: marirs L.NIVETHA AP /CSE - KNCET

Strlwr() function – it is a predefined string function , it is used
to convert the given strings into lower case.
Syntax:
strlwr(string);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“SRIRAM”;
clrscr();
strlwr(name1);
}
o/p: sriram

Strupr() function – it is a predefined string function , it is used
to convert the given strings into upper case.
Syntax:
strupr(string);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]= “sriram”;
clrscr();
strupr(name1);
}
o/p: SRIRAM

Strpbrk() function - it is a predefined string function , it break
the given source string into small sub string based on
pointer break
Syntax:
strpbrk(string1, string2);
Example:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char name1[30]=“welcome”, *p;
clrscr();
p=strpbrk(name1, ‘l’);
printf(“%s”, p);
}
o/p: come L.NIVETHA AP /CSE - KNCET

List of strings
 List of strings is defined as collection of
strings stored in a character.
 you must declare those character variable by
using two dimensional array.
A list of strings stored in two ways:
1.Using an array of strings
2.Using an array of character pointer

Array of strings:
If an application requires to store multiple
strings , an array of strings can be used to
store them.
Here we can store multiple strings using
two dimensional array

Declaration of array of string:
The general form of array of strings is:
<storage class specifier> <Type modifier>
<Type Qualifier> char identifier[<Row_
Specifier>][<Coloumn_Specifier>]=
<Initialization of list of string >
Here the content specified in angular
bracket are optional <>, content in bold letter
are mandatory (char identifier name [][])

Initialization of array of string :
Array of string initialized in two ways:
1. Using string literal constant:
using string literal constant array of string
can be initialized as
char str[][]= {
“ram”,
“mani”
“ramesh”
};

Using list of character initializes:
Using list of character initializer,
an array of string is initialized as.
char str[][]={
{‘r’,’a’,’m’,’0’},
{‘m’,’a’,’n’,’i’,’0’}
};

Reading list of string from the terminal
Here we read list of strings by using scanf()
statement.
Example:
char name[10][20];
for(i=0;i<5;i++)
{
scanf(“%s”, &name[i]);
}

Array of character pointer
array of string also stored in array of
character pointer.
Example:
char *language[]={“java” ,”python”, ”c++”};
Here we store the string by using array of
character pointer ,
also you cannot specify the array size also
not need to declare two dimensional array.

Command Line Argument
 Here the inputs are given to the function by means of
argument.
 by using main function to give the inputs.
 Inputs of the main function given by making use of
special argument known as command line argument.
 In header of the function main , having two parameter.
Example:
main(int argc, char *argv[])
{
statement
…………..
}

argc – the parameter argc sends argument
count , it is in integer type
argv- the parameter argv stands for argument
vector and it is in array of character pointer.
the command line argument are used in the
applications that involve file handling.

Example:comline.c
#include<stdio.h>
int main(int argc , char** argv[])
{
int i=0;
printf("The number of argument are %d", argc);
printf("The argument are ");
for(i=0;i<argc;i++)
printf("%s", argv[i]);
}

Command prompt
C:tcbin>comline source.txt dest.txt
The number of argument are 3
Argument are
C:tcbin>comline.exe
Source.txt
Dest.txt

Function
A function is a set of instructions that are
used to perform specified tasks.
By using function we can divide complex
task into manageable tasks.
Also helps to avoid duplication of work .
Easy to debug and Testing & also improve
maintainability.

Two types of function:
1. User defined function.
2. Pre-defined function. – The library function are
predefined functions. Those functionality has already
been defined. user will use those function but cannot
modify them.
1. User defined function:
The function defined by users according to their
requirement those functions are called user defined
function.
Elements of user defined function:
1.Function declaration
2. Function call
3. Function definition

Function declaration
All the function need to be declared before
they are used
The general form of declaration is :
[return data type] function name(parameters
types );
Here return data type is optional , the
terms in bold letter is mandatory (function
name with () and end with semicolon)

Function declaration
Parameter list type is separated by comma.
The parameter type can be any type(int , float,
*int,….)
also the parameter is optional one. based on
the prototype we specify the parameter.
To specify the parameter combination of
complete parameter declaration and abstract
parameter declaration is allowed.
Example:
int add( int, int );
int add(int x, int y );
int add(int , int y);

Function call
function call is the process of calling the
well defined function
General form of function call is:
function_name(actual parameter);
Here function name with paranthesis ()
and end with semicolon is mandatory.
parameter is optional. based on the
parameter present in the function declaration
to give parameter value with in the function
call.

Example:
#include<stdio.h>
Void main()
{
int add(int , int); function declaration
………………..
………………..
add(10, 20); function call
}

Function definition
function definition is also known as function
implementation.
Every function definition consist of :
1.Header of the function
2.Body of the function

Header of the function:
General form of header of the function is:
[return data type] function name([parameter
list])
Here the terms enclosed in square bracket
is optional, the terms shown in bold letter is
mandatory.
the header function can have only
complete parameter declaration.
here we cannot have abstract parameter
declaration.

Body of the function:
The body of the function consist of set of
statement enclosed with in braces.
The body of the function can have
executable and non-executable statement .
The non-executable statement present
before the executable statement.
Here only to implement logic of the
program.

Function definition
Syntax:
return data type function name(parameter)
{
body of the function;
……………….
…………
return statement;
}

#include<stdio.h>
#include<conio.h>
void main()
{
int add(int , int);
int k;
clrscr();
k=add(10,20); // function call
printf(“The value of k is %d”, k);
getch();
}
Int add(int x , int y) //function definition
{
int z;
z= x+y;
return(z);
}
o/p:
The value of k is 30

Types of parameter:
Parameter are called variable or value passed by
the function, there are two types:
Actual and formal parameter.
Actual parameter:
Actual parameter is present in the function call, it
may be value or reference of the variable
Example:
main()
{
int a , b;
int add(int , int ); function declaration
……. Actual parameter
…….
add(a,b); function call
} L.NIVETHA AP /CSE - KNCET

Formal parameter:
It is present in the function definition
header.it is also called as dummy parameter.
Function definition: Formal parameter
int add(int x , int y)
{
body of the statement;
……………..
……………….
return statement ;
}

Function call/function invocation
depending upon the input and output it is
classified as.
1.Function with no input and no output.
2.Function with input and output.
3.Function with input and no output.
4.Function no input and with output.

Function with no argument and no return value
Syntax:
void main()
{
Void function_name(void);
statement
……….
function_name ();
}
void function_name ()
{
………..
statement
}

Example:
#include<stdio.h>
#include<conio.h>
void main()
{
void message(void); function declaration
message( ); function call
printf(“welcome”);
}
void message() function definition
{
printf(“hello”);
}
o/p: hello welcomeL.NIVETHA AP /CSE - KNCET

Function with argument and with return value
Syntax:
void main()
{
int function_name (int , int );
statement;
……….
c=function_name (v1,v2);
…….
}
int function_name (int v1,int v2)
{
………..
return(z);
}

#include<stdio.h>
#include<conio.h>
void main()
{
int add(int , int);
int k;
clrscr();
k=add(10,20);
printf(“The value of k is %d”, k);
}
Int add(int x , int y)
{
int z;
z= x+y;
return(z);
}
o/p:
The value of k is 30

Function with argument and no return value
Syntax:
void main()
{
void function_name(int, int );
………
……….
function_name (v1,v2);
…….
}
void function_name (int v1,int v2)
{
………..
statement
}

#include<stdio.h>
#include<conio.h>
void main()
{
void add(int , int);
clrscr();
add(10,20);
}
void add(int x , int y)
{
int z;
z= x+y;
printf(“Result is: %d”, z);
}
o/p:
Result is: 30

Function with out argument and with return value:
Syntax:
void main()
{
int function_name(void);
………
……….
c=function_name (void);
…….
}
int function_name ()
{
………..
statement
return();
} L.NIVETHA AP /CSE - KNCET

#include<stdio.h>
#include<conio.h>
void main()
{
int add(void);
int c;
clrscr();
c=add();
printf(“The value of c is %d”, c);
getch();
}
int add()
{
int x=10 , y=20 , z;
z= x+y;
return(z);
}
o/p:
The value of c is 30 L.NIVETHA AP /CSE - KNCET

Parameter passing method in function
If a function is called ,the calling function
to pass some values to the called function.
There are two ways to pass the parameter :
1.Call by value (or) pass by value
This will pass the values from calling
function to called function
Here it will copy the actual parameter
value into formal parameter.
2. Call by reference (or) pass by reference

Call by value (or) pass by value
#include<stdio.h>
#include<conio.h>
Void main()
{
void swap(int , int );
int a , b ;
clrscr();
a=10;
b=20;
printf ( “Before swap values are
%d%d” , a, b );
swap(a,b) ;
printf ( “After swap values are
%d%d” , a, b );
getch();
}
void swap(int x , int
y)
{
int temp;
temp = x;
x = y;
y = temp;
printf ( “In swap
function values are
%d%d” , x , y );
}
o/p:
10 , 20
20 , 10
10 , 20

2. Call by reference (or) pass by reference
This will pass the parameter address or
reference from calling function to called
function
Here it will copy the actual parameter
address into formal parameter.
If the arguments are passed through
reference the changes made in formal
parameter it will affect actual parameter.

Call by reference (or) pass by
reference
#include<stdio.h>
#include<conio.h>
Void main()
{
int swap(int * , int *);
int a , b ;
clrscr();
a=10;
b=20;
printf ( “Before swap
values are %d%d” ,
a, b );
swap( &a, &b) ;
printf ( “After swap
values are %d%d” , a, b );
getch();
int swap(int *x , int * y)
{
int temp;
temp = * x;
* x = * y;
* y = temp;
printf ( “In swap function values
are %d%d” , * x , * y );
}
o/p:
10 , 20
20 , 10
20 , 10

Recursion
Recursion is a process by which a function
calls itself repeatedly until some specified
condition has been specified.
Recursion can be used to solve the similar
problem of smaller size.
Recursion is a technique that breaks a
problem into one or more sub problems that
are similar to the original problem.

Recursion is classified as
1. Direct and indirect recursion
2. Tail and non tail recursion.
Direct recursion:
If a function is directly recursive then it is
calls itself.
Indirect recursion.
Indirect recursion occurs when a function
calls another function

#include<stdio.h>
#include<conio.h>
Void main()
{
int fact (int);
int n = 5 , re ;
clrscr();
re = fact(n);
printf(“%d ”, re);
}
int fact( int x)
{
if( x==1)
return(1);
else
return( x* fact(x-1));
}

2. Tail recursion / non tail.
Tail recursion:
In tail recursion last operation of a function
is a recursively called again and again, here
no pending operation to be performed from
the recursive call

#include<stdio.h>
#include<conio.h>
Void main()
{
int fact (int , int );
int n =5 , re;
clrscr();
re = fact( n , 1 );
printf(“%d ”, re);
}
int fact( int x , int result)
{
if( x==1)
return (result) ;
else
return( fact( x-1 , x*result));
}

Non Tail recursion:
In non tail recursion it is like normal
recursive function it is called itself again and
again, here pending operation to be
performed from the recursive call

Passing arrays to functions
like simple variable , arrays can also be
passed to functions
There are two types:
1.Passing individual element of an array one by
one.
2. Passing the entire array at a time.

Passing individual element of an array:
 Individual elements in an array can be passed
by value or by reference,
 However this way of passing values not
preferable.
 because the elements in an array is large,
then we will pass entire element will take
large number of function calls.
 here we will pass individual element in each
function call.

Passing one dimensional array to function:
To pass the one dimensional array by one
by one or entire value by using reference.

#include<stdio.h> //pass by value
void main()
{
int sum_array(int, int );
int arr[10], n,i,sum=0;
n=5;
printf("enter array element ");
for(i=0;i<n;i++)
scanf("%d", &arr[i]);
for(i=0;i<n;i++)
{
sum=sum_array(arr[i],sum);
}
printf("sum is %d", sum);
}
6 35
int sum_array(int element , int sum)
{
return((sum+element));
}
35+6 L.NIVETHA AP /CSE - KNCET

#include<stdio.h> //pass by reference
void main()
{
int sum_array(int, int );
int arr[10], n,i,sum=0;
n=5;
printf("enter array element ");
for(i=0;i<n;i++)
scanf("%d", &arr[i]);
for(i=0;i<n;i++)
{
sum=sum_array(&arr[i],sum);
}
printf("sum is %d", sum);
}
int sum_array(int *element,int sum)
{
return((sum + *element));
}

Passing the entire array at a time
passing entire array at a time is a preferred
way of passing arrays to functions,
Here we pass the entire array by using
reference or value.

#include<stdio.h>
void main()
{
void display(int[]);
int a[10],i;
printf("Enter the array elementn");
for(i=0;i<5;i++)
scanf("%d",&a[i]);
display(a);
}
void display(int a[])
{
int i;
printf("the array elements are");
for(i=0;i<5;i++)
{
printf("%dn",a[i]);
}
}

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