string , pointer

Bangladesh University ofBusiness & Technology
(BUBT)
Rupnagar , Mirpur-2, Dhaka-1216, Bangladesh
Assignment
o Course Title: Structured Programming Language
o Course Code: CSE 111
o Semester: Summer 2016
o Program: CSE
o Intake: 32nd
o Section: 04
Submitted By : Submitted TO:
Arafat Bin Reza Md. Atiqur Rahman
ID:15162103170 Assistant Professor Dept. of CSE
Phone Number: 01763061221

Strings
WHAT IS STRINGS?
Strings are actually one-dimensional array of characters terminated by
a null character '0'. Thus a null-terminated string contains the characters
that comprise the string followed by a null. These are often used to
create meaningful and readable programs.
Declaringand Initializing a string variables:
There are different ways to initialize a character array variable.
char name [13] = “BUBT CSE "; //valid character array initialization
char name [10] = {‘A’, ‘t’, ‘i’, ‘q’, ‘u',‘r','0’ }; //valid initialization
when you initialize a character array by listings all its characters
separately then you must supply the '0' character explicitly.
We can use pointers to a character array to define simple strings.
char * name = "John Smith";
String Input and Output:
Input function scanf () can be used with %s format specifier to read a
string input from the terminal. But there is one problem
with scanf() function, it terminates its input on first white space it
encounters. Therefore, if you try to read an input string "Hello World"
using scanf() function, it will only read Hello and terminate after
encountering white spaces.

However, C supports a format specification known as the edit set
conversion code %[^n] that can be used to read a line containing a
variety of characters, including white spaces.
Another method to read character string with white spaces from terminal
is gets() function.
Example of string with scanf() function:
#include<stdio.h>
#include<conio.h>
#include<string.h>
int main()
{
char str[20];
printf("Enter a string :n");
scanf("%[^n]",&str);
printf("%s",str);
}
Output:

Example of string with gets () function:
#include<stdio.h>
#include<conio.h>
#include<string.h>
int main()
{
char str[20];
printf("Enter a string");
gets(str);
printf("%s",str);
}
Output:

String Handling Functions:
C language supports a large number of string handling functions that can
be used to carry out many of the string manipulations. These functions
are packaged in string.h library. Hence, you must include string.h header
file in your program to use these functions.
The following are the most commonly used string handling functions.
strcmp () and strcmpi () functions are almost same but the difference
between them is strcmp () function is case sensitive and strcmpi ()
function is not case sensitive.

strcat () function:
#include <stdio.h>
#include <string.h>
int main () {
char str1[12] = "BUBT";
char str2[12] = "CSE";
strcat( str1, str2);
printf("strcat( str1, str2): %sn", str1 );
return 0;
}
Output:

Strcpy () Function:
#include <stdio.h>
#include <string.h>
int main () {
char str1[12] = "BUBT";
char str2[12] = "CSE";
char str3[12];
strcpy(str3, str1);
printf("strcpy( str3, str1) : %sn", str3 );
return 0;
}
Output:

strlen () Function:
#include <stdio.h>
#include <string.h>
int main () {
char str1[12] = "Hello";
char str2[12] = "World";
int len ;
len = strlen(str1);
printf("strlen(str1) : %dn", len );
return 0;
}
Output:

strcmp () Function:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char str1[20],str2[20]={"BANGLADESH"};
printf("ENTER YOUR COUNTRY NAME : ");
scanf("%[^n]",&str1);
if(strcmp(str1,str2)==0)
printf("Your Answer Is Right");
else
printf("Your Answer Is Wrong");
getch();
}
Output:

strcmpi () Function:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char str1[20],str2[20]={"BANGLADESH"};
printf("ENTER YOUR COUNTRY NAME : ");
scanf("%[^n]",&str1);
if(strcmpi(str1,str2)==0)
printf("Your Answer Is Right");
else
printf("Your Answer Is Wrong");
getch();
}
Output:

Difference between strcmp Function and strcmpiFunction:

Searching with string:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
char str1[100],str2[100]={"bangladesh university of business and
technology"},word[50],a,b,x;
printf("ENTER YOUR UNIVERSITY NAME : ");
gets(str1);
gets(word);
if(strcmp(str1,str2)==0)
{
for(a=0;a<strlen(str1);a++)
{
if(word[0]==str1[a])
{
x=1;
for(b=1;b<strlen(word);b++)
{
if(str1[++a]==word[b])

x++;
else
break;
}
}
if(x==strlen(word))
{
printf("The Word Is Found");
break;
}
}
if(x!=strlen(word))
{
printf("The Word Is Not Found");
}
}
else
printf("Give Your University Name Correctly");
getch();
}

Sorting
#include <stdio.h>
#include <stdlib.h>
#include<string.h>
int main()
{
char word[100][100],temp[100];
int i,j,k,p;
printf("How many words you would like to give as an input:");
scanf("%d",&p);
for(i=0; i<p; i++)
scanf("%s",word[i]);
printf("nSortingn");
for (i=0; i<p;i++)
for(j=0;j<p-i-1;j++)
if(strcmp(word[j],word[j+1])>0)
{
strcpy(temp,word[j]);
strcpy(word[j],word[j+1]);
strcpy(word[j+1],temp);

}
for(i=0;i<p;i++)
printf("%st",word[i]);
return 0;
}
Output:

Pointer
WHAT IS Pointer?
Pointers are variables that hold address of another variable of same data
type.
Benefit of using pointers:
 Pointers are more efficient in handling Array and Structure.
 Pointer allows references to function and thereby helps in passing of
function as arguments to other function.
 It reduces length and the program execution time.
 It allows C to support dynamic memory management.

Declaring a pointer variable:
General syntax of pointer declaration is,
data-type *pointer_name;
Data type of pointer must be same as the variable, which the pointer is
pointing. void type pointer works with all data types, but isn't used
oftenly.

Initialization of Pointer variable:
Pointer Initialization is the process of assigning address of a variable
to pointer variable. Pointer variable contains address of variable of same
data type. In C language address operator & is used to determine the
address of a variable. The & (immediately preceding a variable name)
returns the address of the variable associated with it.
int a = 10 ;
int *ptr ; //pointer declaration
ptr = &a ; //pointer initialization
or,
int *ptr = &a ; //initialization and declaration together
Pointer variable always points to same type of data.
float a;
int *ptr;
ptr = &a; //ERROR, type mismatch

Dereferencing of Pointer:
int a,*p;
a = 10;
p = &a;
printf("%d",*p); //this will print the value of a.
printf("%d",*&a); //this will also print the value of a.
printf("%u",&a); //this will print the address of a.
printf("%u",p); //this will also print the address of a.
printf("%u",&p); //this will also print the address of p.

prime number with pointer:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
int n,c,i;
scanf("%d",&n);
for(i=2;i<=n;i++)
{
if(c=n%i)
c++;
if(c==0)
printf("prime : ");
else
printf("not prime");
}
return 0;
}

Accessing Structure Members with Pointer:
To access members of structure with structure variable, we used the
dot . operator. But when we have a pointer of structure type, we use
arrow -> to access structure members.
struct Book
{
char name[10];
int price;
}
int main()
{
struct Book b;
struct Book* ptr = &b;

ptr->name = "Dan Brown"; //Accessing Structure Members
ptr->price = 500;
}

string , pointer

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