DS – Strings in C

String:

• String is a one-dimensional character array.
• String is a collection symbols (alphabets, digits and special symbols).
• Strings must be represented with double quotes.

Syntax:             char identity[size];

Example:             char name[20];

Memory representation:

• We can store only ‘n-1’ characters into an array of size ‘n’.
• Last character of every string is ‘\0’
• ASCII value of ‘\0’ character is 0.

String Format Specifier(%s):

• We use %s to read and display strings.
• To process character by character, we use %c specifier.

Program to display String:

#include<stdio.h> int main() {             char str[20] = “Hello” ;             printf(“%s all \n” , str);              return 0; }

strlen() : strlen() returns length of string excluding null character.

• Return type is size_t (positive integer)
• Prototype is   size_t  strlen(char s[]);

#include<string.h> int main() {             char str[20];             size_t len;             printf(“Enter string : “);             gets(str);             len = strlen(str);             printf(“Length is : %u \n”, len);             return 0; }

Program to find the length of String without using library function:

int main() {             char str[20];             size_t len=0, i=0;             printf(“Enter string : “);             gets(str);             while(str[i] != ‘\0’){                         len++;                         i++;             }             printf(“Length is : %u \n”, len);             return 0; }

Program to convert Upper case characters into Lower case in String:

#include<string.h> int main() {             char src[20];             printf(“Enter Upper string : “);             gets(src);             strlwr(src);                    printf(“Lower string : %s \n”, src);             return 0; }

Program to convert Upper case characters into Lower case without Library function:

#include<stdio.h> #include<string.h> int main() {             char src[20];             int i=0;             printf(“Enter Upper string : “);             gets(src);               while(src[i] != ‘\0’)             {                         if(src[i]>=’A’ && src[i]<=’Z’)                         {                                     src[i] = src[i]+32;                         }                         i++;             }             printf(“Lower string : %s \n”, src); }

Program to reverse the String without using Library function:

#include<string.h> int main() {             char src[20], temp;             int i, j;                         printf(“Enter string : “);             gets(src);               i=0;             j=strlen(src)-1;             while(i<j)             {                         temp = src[i];                         src[i] = src[j];                         src[j] = temp;                         i++;                         j–;             }             printf(“Reverse string : %s \n”, src); }