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C++ Program to Copy One String to Another



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In this article, you will learn and get code on copy one string to another in C++. The program is created with following approaches:

Copy String without using strcpy() Function

This program copies the string (entered by user at run-time) without using any library function like strcpy() Let's have a look at the program first. Its explanation is given later on:

The question is, write a program in C++ that copies one string to another. Here is its answer:

// C++ Copy String without using strcpy() Function
// ----codescracker.com----

#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
    char strOrig[100], strCopy[100], i=0;
    cout<<"Enter the string: ";
    gets(strOrig);
    while(strOrig[i]!='\0')
    {
        strCopy[i] = strOrig[i];
        i++;
    }
    strCopy[i] = '\0';
    cout<<"\nEntered String: "<<strOrig;
    cout<<"\nCopied String: "<<strCopy;
    cout<<endl;
    return 0;
}

This program was build and run under Code::Blocks IDE. Here is its sample run:

C++ program copy string

Now enter the string say codescracker and press ENTER key to copy it to another string. Here is the final snapshot of its sample run:

copy one string to another c++

The dry run of above program with user input, codescracker goes like:

Copy String using Pointer

This program copies the string using pointer. The question is, write a program in C++ to copy the content of one string to another using pointer. Here is its answer:

// C++ Copy String using Pointer
// ----codescracker.com----

#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
    char strOrig[100], strCopy[100];
    char *origPtr, *copPtr;
    cout<<"Enter the string: ";
    gets(strOrig);
    origPtr = &strOrig[0];
    copPtr = &strCopy[0];
    while(*origPtr)
    {
        *copPtr = *origPtr;
        origPtr++;
        copPtr++;
    }
    *copPtr = '\0';
    cout<<"\nEntered String: "<<strOrig;
    cout<<"\nCopied String: "<<strCopy;
    cout<<endl;
    return 0;
}

Here is its sample run with user input, Hello codescracker

copy string c++

The statement,

origPtr = &strOrig[0];

initializes the initial address of strOrig[] variable. That is its 0th index's address. And the statement,

copPtr = &strCopy[0];

also initializes the 0th index's address of strCopy[]

Note - If a pointer type variable holds address of any variable that contains some values, then anything happened with the variable (pointer) makes changes to original. Because it holds its address, not value. So any operation perform through pointer type variable, directly effects the value at that address.

The * is called as value at operator. And & is called as address of operator.

The statement, origPtr++; means, origPtr now holds next index's address.

So using pointer also, all the character of original string gets copied (in one-by-one manner) to strCopy[]

Copy String using User-defined Function

This program also copies one string to another, but using a user-defined function named cpystr()

// C++ Copy String using User-defined Function
// ----codescracker.com----

#include<iostream>
#include<stdio.h>
using namespace std;
void cpystr(char *, char *);
int main()
{
    char strOrig[100], strCopy[100];
    cout<<"Enter the string: ";
    gets(strOrig);
    cpystr(strOrig, strCopy);
    cout<<"\nEntered String: "<<strOrig;
    cout<<"\nCopied String: "<<strCopy;
    cout<<endl;
    return 0;
}
void cpystr(char *origPtr, char *copPtr)
{
    while(*origPtr)
    {
        *copPtr = *origPtr;
        origPtr++;
        copPtr++;
    }
    *copPtr = '\0';
}

This program produces the same output as of previous program.

Using strcpy() Function

This is the last program that uses a library function of C++, named strcpy() to copy string. It takes two string as its argument. The value of second argument gets copied to first.

// C++ Copy String using strcpy() Function
// ----codescracker.com----

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
int main()
{
    char strOrig[100], strCopy[100];
    cout<<"Enter the string: ";
    gets(strOrig);
    strcpy(strCopy, strOrig);
    cout<<"\nEntered String: "<<strOrig;
    cout<<"\nCopied String: "<<strCopy;
    cout<<endl;
    return 0;
}

Same Program in Other Languages

C++ Online Test


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