Module-2_Strings concepts in c programming

• A string is a sequence of characters terminated by a null character ‘0’.
• ‘0’ is automatically encountered at the end of the string.
Declaration of string
char ch[6] ;
Here, ch is a string which can store a maximum of 5 characters and 1 character is reserved for
‘0’.
Introduction

char ch[6] = “HELLO” ;
char ch[6] = “Good” ;
Initialization of string
ch[0] ch[1] ch[2] ch[3] ch[4] ch[5]
‘H’ ‘E’ ‘L’ ‘L’ ‘O’ ‘0’
ch[0] ch[1] ch[2] ch[3] ch[4] ch[5]
‘G’ ‘o’ ‘o’ ‘d’ ‘0’ ‘0’
char ch[6] = { ‘P’, ‘r’, ‘e’, ‘m’, ‘0’ } ; ch[0] ch[1] ch[2] ch[3] ch[4] ch[5]
‘P’ ‘r’ ‘e’ ‘m’ ‘0’ ‘0’
char ch[6] = “Program” ; ch[0] ch[1] ch[2] ch[3] ch[4] ch[5]
‘P’ ‘r’ ‘o’ ‘g’ ‘r’ ‘a’

Initialization of string
Invalid Initialization
char str3[5];
str3 = “GOOD”;

I/O operations on strings
scanf()
char address[10] ;
scanf(“%s”, address);
gets()
char address[10] ;
gets(address);
Reading Text till ~ is encountered
char line[10] ;
scanf("%[^~]", line);
printf()
char address[10] ;
scanf(“%s”, address);
printf(“%s”, address);
puts()
char address[10] ;
gets(address);
puts(address);

#include<stdio.h>
void main()
{
char line[10] ;
printf("Enter stringn");
gets(line);
printf("The string is: ");
puts(line);
}

#include<stdio.h>
void main()
{
char a[10]="GLOBAL" ;
int i,j;
for(i=0;i<6;i++)
{
for(j=0;j<=i;j++)
printf("%ct", a[j]);
printf("n");
}
}
#include<stdio.h>
void main()
{
char a[10]="GLOBAL" ;
int i,j;
for(i=0;i<6;i++)
{
for(j=0;j<=i;j++)
putchar(a[j]);
printf("n");
}
}

Outputs:
G
G L
G L O
G L O B
G L O B A
G L O B A L
G
GL
GLO
GLOB
GLOBA
GLOBAL

Arithmetic Operations on Characters
To write a character in its integer representation, we may write it as an integer.
char x = ‘a’;
// 97
printf(“%dn”, x);
x = ‘z’–1;
printf(“%dn”, x); // 122-1 = 121
char number[21] = “1988”;
int year = atoi(number);
The function atoi() converts the string “1988” (contained in number) to its numeric equivalent 1988
and assigns it to the integer variable year.
String conversion functions are stored in the header file <std.lib.h>.

Storing strings and Characters

Differences between Strings and Character array

Character literals and String literals

String Input and Output Function

String Manipulation Functions
Function Action
#include<string.h>
strlen() finds the length of a string excluding ‘0’
strcpy() copies one string over another
strcmp() compares two strings
strcat() concatenates two strings
strlwr() Converts the string to lowercase letters
strupr() Converts the string to uppercase letters

String handling Functions
strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
#include<string.h>
void main()
{
char a[21] ;
int len;
printf("Enter a stringn");
gets(a);
len=strlen(a);
printf("The length of the string is: %d", len);
}

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
works similar to string-assignment operator.
Syntax:
strcpy(string1, string2);
Assigns the contents of string2 to string1.
string2 may be a string variable or a string constant.
Example:
strcpy(city, “DELHI”);
will assign the string “DELHI” to the string variable city.
strcpy(city1, city2);
will assign the contents of the string variable city2 to the string variable city1.
The size of the array city1 should be large enough to receive the contents of
city2.

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
#include<stdio.h>
#include<string.h>
void main()
{
char a[21],b[21] ;
gets(a);
strcpy(b,a);
printf("The copied string is: %s",b);
}

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
Syntax:
strcmp(string1, string2);
It compares string1 with string2 (case sensitive)
Returns 0 if string1==string2
Returns value > 0 if string1 > string2
Returns value < 0 if string1 < string2
Examples:
char name1[21]=“string”, name2[21]=“string”;
strcmp(name1, name2);
strcmp(name1, “John”);
strcmp(“Rom”, “Ram”);

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
#include<stdio.h>
#include<string.h>
void main()
{
char name1[21]="string", name2[21]="string";
int p1, p2, p3, p4;
p1=strcmp(name1, name2);
p2=strcmp(name1, "String");
p3=strcmp(name1, "Lohit");
p4=strcmp("RAM", "ROM");
printf("p1=%dnp2=%dnp3=%dnp4=%dn",p1,p2,p3,p4);
}

char name1[21]="string", name2[21]="string";
int p1, p2, p3, p4;
p1=strcmp(name1, name2);
p2=strcmp(name1, "String");
p3=strcmp(name1, "Lohit");
p4=strcmp("RAM", "ROM");
0 1 2 3 4 5 6 -
-
-
-
20
s t r i n g 0
0 1 2 3 4 5 6 - - 20
- -
name1
name2
s t r i n g 0
0 1 2 3 4 5 6 - - 20
- -
S t r i n g 0
0 1 2 3 4 5
L o h i t 0
0 1 2 3
R A M 0
0 1 2 3
R O M 0

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
Joins two strings together.
Syntax:
strcat(string1, string2);
• string2 is appended to string1.
• It does so by removing the null character at the end of string1 and placing
string2 from there.
• The string at string2 remains unchanged.
• We must make sure that the size of string1 (to which string2 is appended) is
large enough to accommodate the final string.

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
strcat(part1, part2);

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
#include<stdio.h>
#include<string.h>
void main()
{
char name1[10]="abc", name2[10]="xyz";
printf("Before concatenationn");
printf("name1= %sn",name1);
strcat(name1, name2);
printf("After concatenationn");
}

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
Used to convert a given string into lowercase.
Syntax:
strlwr(string);
#include<stdio.h>
#include<string.h>
void main()
{
char a[21]="C PROGRAM";
printf("Original string= %sn",a);
strlwr(a);
printf("Converted string= %sn",a);
}

strlen()
strcpy()
strcmp()
strcat()
strlwr()
strupr()
Used to convert a given string into uppercase.
Syntax:
strupr(string);
#include<stdio.h>
#include<string.h>
void main()
{
char a[21]="good morning";
printf("Original string= %sn",a);
strupr(a);
printf("Converted string= %sn",a);
}

Programs on strings
1. Write a C program, which reads your name
from the keyboard and outputs a list of
ASCII codes, which represent your name.
#include<stdio.h>
#include<string.h>
void main()
{
char name[21] ;
int i,len;
printf("Enter your name:n");
gets(name);
len=strlen(name);
printf("The name is ASCII form:n");
for(i=0;i<len;i++)
printf("%d",name[i]);
}

Programs on strings
2. Write a C program to find
length of a string without using
library function.
#include<stdio.h>
void main()
{
char a[21] ;
int len=0, i;
gets(a);
for(i=0;a[i]!='0';i++)
len++;
printf("The length of the string is: %d", len);
}

Programs on strings
3. Write a C program to input a string, convert lowercase letters to uppercase and vice
versa without using library functions.
#include <stdio.h> for(i=0;i<len;i++)
#include<string.h> {
void main() if(a[i]>='A' && a[i]<='Z')
{ a[i]=a[i]+32;
char a[21]; else if(a[i]>='a' && a[i]<='z')
int i, len; a[i]=a[i]-32;
printf("Enter a stringn"); }
gets(a); printf("The modified string is %s", a);
len=strlen(a); }

Programs on strings
4. Write a C program to find total number of alphabets, digits in a string without using library
functions.
#include <stdio.h> for(i=0;i<len;i++)
#include<string.h> {
void main() if((a[i]>='A' && a[i]<='Z') || (a[i]>='a' && a[i]<='z'))
{ alpha++;
char a[21]; else if(a[i]>='0' && a[i]<='9')
int i, len, alpha=0, digit=0; digit++;
printf("Enter a stringn"); }
gets(a); printf("No. of alphabets=%dnNo. of digits=%d", alpha, digit);
len=strlen(a); }

Programs on strings
5. Write a C program to count total number of vowels and consonants in a string.
#include<stdio.h>
#include<string.h>
void main()
{
char a[21];
int i, len, vow=0, cons=0;
gets(a);
strupr(a);
len=strlen(a);
for(i=0;i<len;i++)
{
if (isalpha(a[i]))
{
if(a[i]=='A' || a[i]=='E' || a[i]=='I' || a[i]== 'O' || a[i]=='U')
vow++;
else cons++;
}
}
printf("No. of vowels = %dn", vow);
printf("No. of consonants = %dn", cons);
}

Program to Sort String Characters in C
for (i = 0; i < n-1; i++)
{
for (j = i+1; j < n; j++)
{
if (string[i] > string[j])
{
temp = string[i];
string[i] = string[j];
string[j] = temp;
}
}
}
printf("String after sorting - %s n", string);
return 0;
}
#include <stdio.h>
#include <string.h>
int main (void)
{
char string[] = "simplyeasylearning";
char temp;
int i, j;
int n = strlen(string);
printf("String before sorting - %s n", string);

Program to Reverse String in C
#include <stdio.h>
int main() {
char s1[] = "TajMahal"; // String Given
char s2[8]; // Variable to store
reverse string
int length = 0;
int loop = 0;
while(s1[length] != '0’)
{
length++;
}
printf("nPrinting in reverse - ");
for(loop = --length; loop>=0; loop--)
printf("%c", s1[loop]);
loop = 0;
printf("nStoring in reverse - ");
while(length >= 0)
{
s2[length] = s1[loop];
length--;
loop++;
}
s1[loop] = '0'; // Terminates the string
printf("%sn", s2);
return 0;
}

Program to Swap Strings in C
#include <stdio.h>
int main()
{
char s1[] = "TajMahal";
char s2[] = "Dazzling";
char ch;
int index = 0;
//Character by Character
approach
printf("Before Swapping - n");
printf("Value of s1 - %s n", s1);
while(s1[index] != '0’)
{
ch = s1[index];
s1[index] = s2[index];
s2[index] = ch;
index++;
}
printf("After Swapping - n");
return 0;
}

String Copy Program in C
#include <stdio.h>
int main() {
char s1[] = "TajMahal"; // String
Given
char s2[8]; // Variable to hold
value
int length = 0;
while(s1[length] != '0’)
{
s2[length] = s1[length];
length++;
}
s2[length] = '0'; // Terminate the string
printf("Value in s1 = %s n", s1);
printf("Value in s2 = %s n", s2);
return 0;
}

Program to Compare Strings in C
#include <stdio.h>
int main()
{
char s1[] = "advise";
char s2[] = "advice";
int n = 0;
unsigned short flag = 1;
while (s1[n] != '0’)
{
if(s1[n] != s2[n])
{
flag = 0;
break;
}
n++;
if(flag == 1)
{
printf("%s and %s are identicaln", s1, s2);
}
else
{
printf("%s and %s are NOT identicaln", s1, s2);
}
return 0;
}

Program to Concatenate Strings in C
#include <stdio.h>
#include <string.h>
int main()
{
char s1[10] = "Taj";
char s2[] = "Mahal";
int i, j, n1, n2;
n1 = strlen(s1);
n2 = strlen(s2);
j = 0;
for(i = n1; i< n1+n2; i++ )
{
s1[i] = s2[j];
j++;
}
s1[i] = '0';
printf("%s", s1);
return 0;
}

Implementing a Palindrome String Program in C
#include <stdio.h>
#include <string.h>
int main()
{
char string[100], rev_string[100];
printf("Enter a string: ");
gets(string);
strcpy(rev_string, string);
strrev(rev_string);
if(strcmp(string, rev_string) == 0)
printf("%s is a palindrome string.n", string);
else
printf("%s is not a palindrome string.n", string);
return 0;
}

#include <stdio.h>
#include <string.h>
int main()
{
char str[] = { "abbba" };
// Start from first and
// last character of str
int l = 0;
int h = strlen(str) - 1;
WITHOUT USING LIBRARY FUNCTIONS
// Keep comparing characters while they are same
while (h > l)
{
if (str[l++] != str[h--])
{
printf("%s is not a palindromen", str);
return 0;
// will return from here
}
}
printf("%s is a palindromen", str);
return 0;
}

String/Data Conversion Example

2.6 String/Data Conversion
• A common set of applications, format data by either converting a sequence of
characters into corresponding data types or vice versa.
• Two such applications are parsing and telecommunications.
• C already has an extensive set of data conversion functions created for scanf and
printf.

String to Data conversion
• The string scan function is called sscanf ().
• This function scans a string as though the data were coming from a file.
• Just like fscanf (), it requires a format string to provide the formatting parameters for
the data.
• All fscanf () format codes are valid for the scan memory functions.
• Like fscanf (), the scan memory functions also return the number of variables
successfully formatted.
• If they attempt to "read" beyond the end of string-they return an end-of-file flag.
• The basic concept is shown in Figure 11-24.

String to Data conversion
sscanf() is a function used to read formatted input from a string.
It stands for "String Scan Formatted".
It is part of the C Standard Library and is declared in the <stdio.h> header file.
Syntax/The function prototype of sscanf() is:
int sscanf(const char *str, const char *format, ...);
Here,
• str is the string from which data is to be read.
• format is a format string that specifies how to interpret the data in the string str.
• The ellipsis ... indicates that sscanf() can accept a variable number of arguments. These arguments
are pointers to the variables where the extracted data will be stored.
NOTE:
Sscanf() is one-to-many function.
It splits one string into many variables.

Example for sscanf()
#include <stdio.h>
int main() {
char str[] = "John 25 123.45";
char name[20];
int age;
float salary;
sscanf(str, "%s %d %f", name, &age, &salary);
printf("Name: %sn", name);
printf("Age: %dn", age);
printf("Salary: %.2fn", salary);
return 0;
}
OUTPUT:
Name: John
Age: 25
Salary: 123.45

Data to String Conversion
• The string print function sprintf() follows the rules of fprintf().
• Rather the sending the data to a file, however, it simply "writes" them to a
string.
• When all data have been formatted to the string, a terminating null character
added to make the result a valid string.
• If an error is detected, sprintf() returns any negative value, traditionally EOF.
• If the formatting is successful, it returns the number of characters formatted,
not counting the terminating null character.
• The string print operation is shown in Figure 11-25.

• sprintf() is a function used to write formatted data to a string.
• It stands for "String Print Formatted".
• It is part of the C Standard Library and is declared in the <stdio.h> header file.
Syntax/The function prototype of sprintf() is:
int sprintf(char *str, const char *format, ...);
Here,
• str is the character array (string) where the formatted data will be stored.
• format is a format string that specifies how the data should be formatted.
• The ellipsis ... indicates that sprintf() can accept a variable number of
arguments. These arguments are the values to be formatted and inserted into the
string according to the format string.

Example for sprintf()
#include <stdio.h>
int main() {
char str[100];
int age = 25;
float salary = 123.45;
sprintf(str, "My age is %d and my salary is %.2f", age, salary);
printf("%sn", str);
return 0;
}
OUTPUT:
My age is 25 and my salary is
123.45
NOTE:
Sscanf() is many-to-one function.
It joins many pieces od data into one string.

Module-2_Strings concepts in c programming

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