C Program to Concat Two Strings without Using Library Function

Program : C Program to Concat Two Strings without Using Library Function

Program Statement :

In this C Program we have to accept two strings from user using gets and we have to concatenate these two strings without using library functions.

#include<stdio.h>
#include<string.h>
void concat(char[], char[]);
int main() {
   char s1[50], s2[30];
   printf("\nEnter String 1 :");
   gets(s1);
   printf("\nEnter String 2 :");
   gets(s2);
   concat(s1, s2);
   printf("nConcated string is :%s", s1);
   return (0);
}
void concat(char s1[], char s2[]) {
   int i, j;
   i = strlen(s1);
   for (j = 0; s2[j] != '\0'; i++, j++) {
      s1[i] = s2[j];
   }
   s1[i] = '\0';
}

#include<stdio.h>

#include<string.h>

void concat(char[], char[]);

int main() {

char s1[50], s2[30];

printf("\nEnter String 1 :");

gets(s1);

printf("\nEnter String 2 :");

gets(s2);

concat(s1, s2);

printf("nConcated string is :%s", s1);

return (0);

}

void concat(char s1[], char s2[]) {

int i, j;

i = strlen(s1);

for (j = 0; s2[j] != '\0'; i++, j++) {

s1[i] = s2[j];

}

s1[i] = '\0';

}

Output of Program :

Enter String 1 : Pritesh
Enter String 2 : Taral
Concated string is : PriteshTaral

Enter String 1 : Pritesh

Enter String 2 : Taral

Concated string is : PriteshTaral

Explanation of Code :

Our program starts from main and we are accepting two strings from user using these following statements -

printf("\nEnter String 1 :");
gets(s1);
printf("\nEnter String 2 :");
gets(s2);

printf("\nEnter String 1 :");

gets(s1);

printf("\nEnter String 2 :");

gets(s2);

Inside the concate() function we are firstly calculating the size of first string.

i = strlen(s1);

1	i = strlen(s1);

Now we are iterating 2nd string character by character and putting each character to the end of the 1st string.

Explanation of Program With Dry Run :

Step 1 : Input

s1 = "Pritesh"
s2 = "Taral"

1 2	s1 = "Pritesh" s2 = "Taral"

Step 2 : Size of Strings

i = strlen(s1);
  = strlen("Pritesh");
  = 7

i = strlen(s1);

= strlen("Pritesh");

= 7

Step 3 : Concatenating Strings

Last position of s1 = 7

1	Last position of s1 = 7

First Character of the 2nd String will be stored at last Position of String 1. thus using for loop -

s1[7]  = "T"
s1[8]  = "a"
s1[9]  = "r"
s1[10] = "a"
s1[11] = "l"

s1[7] = "T"

s1[8] = "a"

s1[9] = "r"

s1[10] = "a"

s1[11] = "l"

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