Pointers in C

A Pointer is a variable in C that contains address of another variable.

A pointer variable is denoted by

int *p; //This means p is a pointer to an integer variable

* is Value at Address operator

& is Address of Operator

int x =15; //x is an integer variable

int *ptr1 = &x //Now p contains the address of x..i.e ptr is a pointer to x

int **ptr2 = &ptr1 //And ptr2 contains the address of ptr1..so prt2 is a pointer to a pointer


#include <stdio.h>
#include <conio.h>

int main()
{
    int x=15;
    int *ptr1;
    int **ptr2;

    ptr1 = &x; //Now ptr contains the address of x
    ptr2 = &ptr1; //ptr2 contains the address of ptr

    printf("\nAddress of x = %u", &x);
    printf("\nValue of x = %d", x);
    printf("\nValue of x = %d", *(&x));

    printf("\n ");
    printf("\nAddress of ptr1 = %u", &ptr1);
    printf("\nValue of ptr1 / Address of x = %d", ptr1);
    printf("\nValue at address pointed by ptr1/Value of x = %d", *ptr1);

    printf("\n ");
    printf("\nAddress of ptr2 = %u", &ptr2);
    printf("\nValue of ptr2 / Address of ptr1 = %d", ptr2);
    printf("\nValue at address pointed ptr2 / Address of x= %d", *ptr2);
    printf("\nValue at address pointed by ptr1 which is pointed by ptr2/Value of x = %d", **ptr2);

    getch();
    return 0;
}

Snapshot of the o/p

A Simple C Program

Hello Friends,

This is a very simple C Program demonstrating input, output using printf(), scanf() functions in C. It also shows how to write and call some simple functions in C without any argument or return type.

Level- Beginner

  Program demonstrating Simple Functions, input, output in C

Hello.c


#include<stdio.h>
#include<conio.h>

void hello_message()
{
     printf("\n Hello World!! :)\n");
}

void bye_message()
{
     printf("\n Good Bye World!!!\n");
}

void main()
{
     int num, a, b, c;
     a=5;
     b=7;
     printf("\n ~~~Welcome to the world of C~~~ \n");
     /*
     This is not allowed gives error
     printf("\n Hello

     ");*/

     hello_message();

     printf("\n Enter a Number : ");

     scanf("%d", &num);

     printf("\n You entered %d", num);

     printf("\n c = %d (Garbage Value)", c); //displays garbage value
     c=9;
     printf("\n c = %d", c);//o/p - 9
     printf("\n a = %d", a); //o/p - 5

     printf("\n Experiments with printf \n");

     printf("\n number = %d", 3); // o/p- 3
     printf("\n a+b = %d", a+b); //o/p -12
     printf("\n a*b+c = %d", a*b+c); //o/p-44

     printf("\n Experiments with scanf \n");

     printf("\n Enter three Numbers : ");
     scanf("%d %d %d", &a, &b, &c);
     printf("\n a = %d, b = %d, c = %d ", a,b,c);

     printf("\n Enter three Numbers (separated by commas) : ");
     scanf("%d, %d, %d", &a, &b, &c);
     printf("\n a = %d, b = %d, c = %d ", a,b,c);

     bye_message();
     getch();
}

 Snapshot of the o/p

Simple Program O/P