String operations (length, compare, copy, concatenate) without including string.h using C

In C, string.h includes various build in functions for string operations. The main operations are
1. Length of the string (strlen)
The syntax of strlen is :
 
strlen(string);
 

It calculates the length of the string and returns its length. For example:

 
#include
 
 
string = "Mumbai";
 
 
printf("Length = %d",strlen(string));
 

The above code displays 5 because Mumbai consists of 5 characters. Note: it does not count null character.

2. Joining two strings (strcat)

The syntax of strcat is

 
strcat(string1,string2);
 

Now it removes the null character from string1 and joins the first character of string2 at that position. Now, string1 consists of both string1 and string2 in joined form. Example:

 
#include=
 
 
char string1[] = "Anti";
 
 
char string2[] = "Particle";
 
 
strcat(string1,string2);=
 
 
printf("%s",string1); //display AntiParticle
 

3. Comparing two strings(strcmp)

The syntax of strcmp is

 
strcmp(string1,string2);
 

It returns 0 if string1 is same as string2 and returns 1 if they are not same. Example:

 
#include
 
 
char string1 = "Nepal";
 
 
char string2 = "Srilanka";
 
 
if(strcmp(string1,string2)==0){
 
 
printf("They are equal");
 
 
}else{
 
 
printf("They are not equal"); //this is executed
 
 
} 
 

4. Copying one string to another (strcpy)

The syntax of strcpy is

 
strcpy(destination_string, source_string);
 

It copies the content of source_string to destination_string. Example:

 
#include
 
 
char source[] = "Hello";
 
 
char destination[10]; //uninitialized
 
 
strcpy(destination,source);
 
 
printf("%s",destination); //prints Hello 
 

These are some of the functions in string.h for string operation. To use these functions you must include header file . But we can make our own functions to perform above task without including string,h. Here is the complete source code that has own functions find_length (like strlen) to find the length, join_strings( like strcat) for joining strings, compare_strings(like strcmp) for comparing two strings and copy_string(like strcpy) to copy one string from another. Observer carefully the code, if you are a beginner, you will learn a lot of things about string operation.

Source Code

///fundamental string operation, lenth, concatenation, compare and copy strings without string.h
#
include  #include 
  int find_length(char string[]) {
    int len = 0, i;
    for (i = 0; string[i] != '\0'; i++) {
      len++;
    }
    return len;
  }
void join_strings(char string1[], char string2[]) {
    int i, len1, len2;
    len1 = find_length(string1);
    len2 = find_length(string2);
    for (i = len1; i 

Output