C Program to Concatenate Two Strings

In this tutorial, i am going to show you how to concatenate or join two string with the help of for loop, while loop, function and pointer in c program.

Algorithm and Programs to Concatenate Two Strings in C

  • Algorithm To Concatenate Two Strings
  • C program to Concatenate Two Strings using For Loop
  • C program to Concatenate Two Strings While Loop
  • C program to Concatenate Two Strings using Function
  • C program to Concatenate Two Strings uisng Pointer

Algorithm To Concatenate Two Strings

Follow the below given algorithm to write a program concatenate or join two string; as follows:

  • START
  • Step 1 -> Take two string as str1 and str2.
  • Step 2 -> Move to the last position of first string let it be i.
  • Step 3 -> Now Loop over second string with j = 0
  • Assign the character str1[i] = str2[j]
  • Increment i and j and repeat till the last element of j.
  • End Loop
  • Step 3 -> Print str1.
  • STOP

C program to Concatenate Two Strings using For Loop

/* C program to Concatenate Two Strings without using strcat() */
#include <stdio.h>
#include <string.h>
 
int main()
{
  	char Str1[100], Str2[100];
  	int i, j;
 
  	printf("\n Please Enter the First String :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second String :  ");
  	gets(Str2);
        // To iterate First String from Start to end  
  	for (i = 0; Str1[i]!='\0'; i++);
        // Concatenating Str2 into Str1  	
  	for (j = 0; Str2[j]!='\0'; j++, i++)
  	{
  		Str1[i] = Str2[j];
  	}
  	Str1[i] = '\0';
  	printf("\n String after the Concatenate = %s", Str1);
  	
  	return 0;
}

The result of the above c program; as follows:

Please Enter the First String :  hello
Please Enter the Second String :  world
String after the Concatenate = helloworld

C program to Concatenate Two Strings While Loop

#include <stdio.h>
#include <string.h>
 
int main()
{
  	char Str1[100], Str2[100];
  	int i, j;
 
  	printf("\n Please Enter the First String :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second String :  ");
  	gets(Str2);
 
  	i = 0;
	while( Str1[i]!='\0')
	{
		i++;
	}
	
  	j = 0;
  	while( Str2[j]!='\0')
  	{
  		Str1[i] = Str2[j];
  		i++;
  		j++;
  	}
  	Str1[i] = '\0';
  	printf("\n String after the Concatenate = %s", Str1);
  	
  	return 0;
}

The result of the above c program; as follows:

Please Enter the First String :  hello
Please Enter the Second String :  dear
String after the Concatenate = hellodear

C program to Concatenate Two Strings using Function

#include <stdio.h>
#include <string.h>
void concatenate(char [], char []); 
int main()
{
  	char Str1[100], Str2[100];
 
  	printf("\n Please Enter the First String :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second String :  ");
  	gets(Str2);
  	
  	concatenate(Str1, Str2);
  	printf("\n String after the Concatenate = %s", Str1);
  	
  	return 0;
}
void concatenate(char s1[], char s2[])
{
	int i, j;
	
	i = 0;
	while( s1[i]!='\0')
	{
		i++;
	}
	
  	j = 0;
  	while( s2[j]!='\0')
  	{
  		s1[i] = s2[j];
  		i++;
  		j++;
  	}
  	s1[i] = '\0';
}

The result of the above c program; as follows:

Please Enter the First String :  hello
Please Enter the Second String :  world
String after the Concatenate = helloworld

C program to Concatenate Two Strings uisng Pointer

#include <stdio.h>
#include <string.h>
int main()
{
  	char Str1[100], Str2[100];
  	char *s1 = Str1;
	char *s2 = Str2;
 
  	printf("\n Please Enter the First String :  ");
  	gets(Str1);
  	
  	printf("\n Please Enter the Second String :  ");
  	gets(Str2);
  	
  	while(* ++s1);
  	
  	while(*(s1++) = (*s2++)); 
  	
  	printf("\n String after the Concatenate = %s", Str1);
  	
  	return 0;
}

The result of the above c program; as follows:

Please Enter the First String :  hello
Please Enter the Second String :  world
String after the Concatenate = helloworld

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