The document discusses strings in C programming. It defines strings as finite sequences of characters that can be implemented as arrays of bytes or characters. It describes common string operations like searching, sorting, trimming, insertion, and deletion. It also lists various string manipulation functions in C like strcat, strcpy, strlen, and their applications in areas like text editing, search engines, and computational biology.

1. ASSIGNMENT PRESENTATION – 1
DATA STRUCTURES
TEAM-1
TOPIC: STRING- IMPLEMENTATION, OPERATIONS
AND APPLICATIONS
TEAM MEMBERS:
1.ARUN KUMAR
2.DIVYA
3.GAYATHRI
4.KAVYA
5.MOHANA PRIYA
6.PRASHANTH

2. STRING:
 Finite sequence of characters.
 Data type storing sequence of data values, in bytes
according to character encoding.
 It is null terminated character array. Size of the string is
length of the string plus one.
 Variable is declared to have string data type, holding
some predetermined symbols.
 Represented using double quotes.
Declaration: char name[size];
Formal theory to represent strings:
Let Σ be a non-empty finite set of letters of an
alphabet. Elements of Σ are called symbols or characters.
A string over Σ is any finite sequence of characters from Σ.
EG: if Σ={0,1} then 01101 is a string over Σ.

3. IMPLEMENTATION:
String is a variable length array of characters that is
delimited by null character.
They are implemented as array of bytes, characters or
code units in order to allow fast access to characters in a
string.
Difference between character and string:
String: character:
char str[]=“H”; H 0 char str = ‘H’; H
1. Here H is a string not a
character and they are
enclosed by double quotes.
1. Here H is a character not
a string and they are
enclosed by single quotes.
2. They require two memory
location including the null
character.
2. It requires only single
memory location and it
doesn’t have null character.

4. Compiler assigns character string to a character
array and automatically assigns a null character to the
end of string.
size of the string= length of the string + 1.
There are two types of strings namely:
 Mutable strings: Eg: C++, ruby.
 Immutable strings: Eg: Java, python.
Reading strings:
1. Using scanf function. scanf(“%s”,str);
2. Using gets() function. gets(str);
3. Using getchar() and getche() funtion. getchar(ch);
Writing strings:
1. Using printf function. printf(“%s”,str);
2. Using gets() function. gets(str);
3. Using getchar() and getche() funtion. getchar(ch);

5. Implementing strings using pointers:
This uses a pointer to access the elements.
Eg: #include<stdio.h>
void main()
{
char name[ ]=“hello”, *ptr;
ptr=name;
while(*ptr != ‘0’)
{
printf(“%s”, *ptr);
ptr++;
}
}
Output: hello

6. OPERATIONS:
Searching:
Searching is to find a particular character in a string
or not and to return the position.
Algorithm:
Search(A,N,VAL,POS)
Step 1: [INITIALIZE] SET POS= -1
Step 2: [INITIALIZE] SET I=0
Step 3: Repeat Step 4 while I<N
Step 4: IF A[I] = VAL
SET POS = I
PRINT POS
Go to step 6.
Step 5: PRINT “Value not present in the string”
Step 6: EXIT.

7. Sorting:
Sorting is used to arrange the characters in an array
using some order.
Algorithm:
SORTING(A,N)
Step 1: Repeat Step 2 FOR I = 0 to N-1
Step 2: Repeat step 3 FOR J = 0 to N-1
Step 3: IF A[J]>A[I], then
SWAP A[J] and A[J+1]
[End of Inner and Outer Loop]
Step 4: EXIT.
Trim: String trim(String str);
Returns a string with whitespace stripped from the
beginning and end of the string. Whitespace characters
are n,t,0 and plain space. It also has rtrim() and ltrim().

8. Insertion:
The insertion operation inserts a string s, in the main
text T, at Kth position.
Algorithm: INSERT(text,pos,str)
Step 1: [INITIALIZE] SET I = 0, J = 0 and K=0
Step 2: Repeat step 3 to 4 while text[I] != ‘0’
Step 3: If I=Pos, then
Repeat while str[K] != ‘0’
new_str[J]=str[K]
SET J=J+1 and K=K+1
Else new_str[J] = text[I]
SET J=J+1
Step 4: SET I = I+1
Step 5: SET new_str[J] = ‘0’
Step 6: EXIT.

9. Deletion:
It deletes a substring from a given text.
Algorithm:
Step1: [INITIALIZE] SET I=0 AND J=0
Step 2: Repeat steps 3 to 6 while text[I] != ‘0’
Step 3: If I = Pos, then
Repeat step 4 while n>=0
SET I = 1+1
SET N=N-1
Step 4: SET new_str[J] = text[I]
Step 5: SET J = J+1
Step 6: SET I = I+1
Step 7: SET new_str[J] = ‘0’
Step 8: EXIT

10. String Manipulation Functions:
1.The strcat function
Syntax: char *strcat(char *s1, char *s2);
2.The strncat function
Syntax: char *strncat(char *s1, char *s2, size n);
3.The strchr function
Syntax: char *strchr(char *s1, int c);
4.The strrchr function
Syntax: char *strrchr(char *s1, int c);
5. The strcmp function
Syntax: char *strcmp(char *s1, char *s2);
6. The strncmp function
Syntax: char *strncmp(char *s1, char *s2, size n);

11. 7. The strcpy function
Syntax: char *strcpy(char *s1,char *s2);
8. The strncpy function
Syntax: char *strncpy( char *s1, char *s2, size n);
9. The strlen function
Syntax: int strlen(char *str);
10. The strstr function
Syntax: char *strstr( char *s1, char *s2);
11. The strspn function
Syntax: int strspn(char *s1, char *s2);
12. The strcspn function
Syntax: int strcspn(char *s1, char *s2);
13. The strpbrk function
Syntax: char *strpbrk( char *s1, char *s2);

12. 14.The strtok function
Syntax: char *strtok( char *s1, char *delimiter);
15. The strtol function
Syntax: long strtol(char *str, char **end, int base);
16.The strtod function
Syntax: double strtod(char *str, char **end);
Program:
#include<stdio.h>
#include<string.h>
int main()
{
char str1[50]= “PROGRAMMING”, str2[50]= “IN C”, *pos;
char s1[50]=“HELLO”, s2[50]=“HEY”, s3[10], *ptr;
char delim[3]=“,”, str[50]=“HELLO, TO, THE, WORLD”;
long num;
double n;

13. strcat(str1,str2);
printf(“n Using strcat function: %s”, str1);
strncat(str1,str2,2);
printf(“n Using strncat function: %s”,str1);
pos= strchr(str1, ‘N’);
if(pos)
printf(“n strchr- Character is found at position %d”,
pos);
else
printf(“n strchr- Character not found”);
pos1= strrchr(str1,’M’);
if(pos1)
printf(“n strrchr- last position of character is %d”,
pos1);
else
printf(“n strrchr- Character not found”);

14. if(strcmp(s1,s2)==0)
printf(“n strcmp- Strings are identical”);
else
printf(“n strcmp- Strings are not identical”);
if(strncmp(s1,s2,2)==0)
printf(“n strncmp- Strings are identical”);
else
printf(“n strncmp- Strings are not identical”);
strcpy(s3,s1);
printf(“n strcpy function: %s”,s3);
strncpy(s3,s1,2);
printf(“n strncpy function: %s”,s3);
printf(“n Length of the string: %d”,strlen(s1));

15. ptr=strstr(str1,str2);
if(ptr)
printf(“n strstr- Substring found”);
else
printf(“n strstr- Substring not found”);
printf(“n strspn- Position of character that doesnot
match: %d”,
strspn(str1,str2));
printf(“n strcspn- Position of first character that matches:
%d”, strspn(str1,str2));
*ptr= strpbrk(str2,s3);
if(ptr==NULL)
printf(“n strpbrk- No character matches using pointer”);
else
printf(“n strpbrk- Character matches”);
result=strtok(str, delim);

16. while(result != NULL)
{
printf(“n strtok function: %s”,result);
result= strtok(NULL,delim);
}
num= strtol(“65432 octal”, NULL, 8);
printf(“strtol function: octal value is %ld”, num);
n= strtod(“123.456abcd”,NULL);
printf(“n strtod function: %lf”,n);
returen 0;
}
Output:
Using strcat function: PROGRAMMING IN C
Using strncat function: PROGRAMMING IN
strchr- Character is found at the position: 9

17. strrchr- Last position of character is: 7
strcmp- Strings are not identical
strncmp- Strings are identical
strcpy funcion- HELLO
strncpy function- HE
length of the string- 5
strstr- Substring found
strspn- Position of the string that doesnot match: 3.
strcspn- position of the character that matches: 8.
strpbrk- No characters matches using pointer.
strtok function: HELLO TO THE WORLD.
strtol function: Octal value is 27418.
strtod function: 123.456000

18. APPLICATIONS USING STRING:
1. Pattern matching in computation biology.
2. Text editor, Digital library and search engine.
3. String matching through 2-Dimensional meshes

19. REFERENCES:
 Reema Thareja, “Programming in C”, Oxford University
press, 2011.
 http://en.wikipedia.org/wiki/string_operation
 http://www.stackoverflow.com/string

20. THANK YOU !!!