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d4_Pointers(指针)
Pointers
* Pointers are variables
* Pointers store only address of the memory location.
they do not store a value.
* Pointers are declared like :- int *ptr;
* Address are always integer datatype , hence all pointers need only 2 bytes
#include<stdio.h>void main(){ int a=10; //Integer variable int *ptr; // Pointer variable ptr= &a; // address of a stored in ptr printf("%d\n",a); // prints value printf("%u\n",&a); // %u used to print address printf("%u\n",&ptr); //65526 printf("%u\n",ptr); // 65524 printf("%d\n",*ptr); //10 }
float类型：
#include<stdio.h>void main(){ float b=10.24; float * ptr; // 2bytes float means the data type of the value present at this address ptr = &b; printf("%f\n",b); //10.24 printf("%u\n",&b); // 65524 printf("%u\n",ptr); // 65524 printf("%u\n",&ptr); // 65528 printf("%f\n",*ptr); // 10.24 }
* int a =10; // a Hold the value
* int *ptr=&a // ptr holds the address of variable
* int **ptr=& ptr // ptr1 holds the address of a pointer variable
#include<stdio.h>void main(){ int a=10; int * ptr; //single pointer int ** ptr1; //double pointer ptr= &a; ptr1= &ptr; printf("%d\n",a); //10 printf("%u\n",ptr); //65524 %u： 输出地址 printf("%u\n",&ptr); //65526 printf("%u\n",*ptr); // 10 printf("%u\n",ptr1); // 65526 printf("%u\n",&ptr1); // 65528 printf("%u\n",*ptr1); // 65524 printf("%u\n",**ptr1); // 10 }
Use of pointers：
#include<stdio.h>void swap(int *x,int *z); void main() { int a=10, b=20; swap(&a,&b); //call by reference printf(" a = %d",a); printf(" b = %d",b); } void swap(int *x,int *z) { int temp; temp=*x; *x=*z; *z=temp; }
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