Pointers in C

                                                          Pointers in C


   Simply a pointer is variable which holds the address of another variable.
   Then What is the differnce between the a normal variable and pointer variable?
   What happens when we declare the variable like

      int a=34;
     
  The above declaration tells the compiler that 'a' is a integer variable and reserves two bytes of memory for 'a'.
   Now the question is where the 'a' is in memory?
   
      well do u remember the scanf function?

    scanf("%d",&a);
 
in scanf fucntion there is a symbol '&' nothing but it represents the address of the variable 'a' in memory(for example 1024 address)

While using pointers we use * and &

 declaration of pointer variable:
      datatype * variable=value;
     here datatype is int float or char or even void data type
   
     for example int *a;
     here 'a' is a integer pointer i.e, it can store only integer address
     
    int *b;
    int c=10;
    b=&c;
     now b conatins the address of c.
   
    /*pointers in c*/
   
     main()
     {
      int *p;
      int q=20;/*pointer variable declaration*/
      p=&q;
      printf("\nvalue of q is %d ",q);
      printf("\nvalue of q is %d ",*(&q));
      printf("\nvalue of q is %d ",*p);
      printf("\nAddress of q is %u ",p);
      printf("\nAddress of q is %u ",&q);
     }
    output:
        value of q is 20
        value of q is 20
        value of q is 20
        address of q is 1190
        address of q is 1190


/*  swapping of two numbers using pointers*/

    void swap(int *,int *);
    void main()
    {
       int a=5,b=6;
       printf("before swapping a=%d\tb=%d",a,b);
      swap(&a,&b);
      printf("after swapping a=%d\tb=%d",a,b);
   }
    void swap(int *p,int *q)
   {
     int temp;
   temp=*p;
   *p=*q;
   *q=temp;
   printf("\m after swapping a=%d\tb=%d",a,b);
   }

  output:
   before swapping a=5      b=6
    after swapping a=6      b=5
 
   
                                             phython programming

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