Accessing string using pointer

Using char* (character pointer), we can access the string.

Example

Declare a char pointer

Assign the string base address(starting address) to the char pointer.

char str[6] = "Hello";
char *ptr;

//string name itself base address of the string
ptr = str; //ptr references str

Where,

ptr - is a character pointer which points the first character of the string. i.e. &str[0]

Like normal pointer arithmetic, if we move the ptr by 1 (ptr+1) position it will point the next character.

Printing each character address of a string using pointer variable

Example

/*
 * Program  : printing address of each char in the string
 * using pointer variable
 * Language : C
 */

#include<stdio.h>

int main()
{
    char str[6] = "Hello";
    char *ptr;
    int i;

    //string name itself a base address of the string
    ptr = str; //ptr references str

    for(i = 0; ptr[i] != '\0'; i++)
        printf("&str[%d] = %p\n",i,ptr+i);


    return 0;
}

Printing each character of a string using the pointer

To print the value stored at each char address, we have to dereference the memory address.

Like below,

*(ptr+i)

Example

/*
 * Program  : printing each char in the string
 * using pointer variable
 * Language : C
 */

#include<stdio.h>

int main()
{
    char str[6] = "Hello";
    char *ptr;
    int i;

    //string name itself a base address of the string
    ptr = str; //ptr references str

    for(i = 0; ptr[i] != '\0'; i++)
        printf("str[%d] = %c\n",i,*(ptr+i));


    return 0;
}

Manipulating characters of a string using the pointer

Let's change the 4th(index 3) character 'l' as 'o'.

The new string will be "Heloo".

Example

/*
 * Program  : Manipulating string using pointer
 * Language : C
 */

#include<stdio.h>

int main()
{
    char str[6] = "Hello";
    char *ptr;
    int i;

    printf("String = %s\n", str);

    //string name itself a base address of the string
    ptr = str; //ptr references str

    //change the 4th char as 'o'
    *(ptr+3) = 'o';

    printf("Updated string = %s\n",str);

    return 0;
}