c语言指针示例_C中的空指针示例

c语言指针示例

空指针 (NULL pointer)

The word "NULL" is a constant in C language and its value is 0. In case with the pointers - if any pointer does not contain a valid memory address or any pointer is uninitialized, known as "NULL pointer". We can also assign 0 (or NULL) to make a pointer as "NULL pointer".

单词“ NULL”是C语言中的常量，其值为0 。 如果使用指针-如果任何指针不包含有效的内存地址或任何指针未初始化，则称为“ NULL指针” 。 我们还可以将0 (或NULL )分配为“ NULL指针” 。

Example:

例：

In this example, there are 3 integer pointers ptr1, ptr2 and ptr3. ptr1 is initialized with the address of the integer variable num, thus ptr1 contains a valid memory address. ptr2 is uninitialized and ptr3 assigned 0. Thus, ptr2 and ptr3 are the NULL pointers.

在此示例中，有3个整数指针ptr1 ， ptr2和ptr3 。 ptr1用整数变量num的地址初始化，因此ptr1包含有效的内存地址。 ptr2未初始化，并且ptr3分配为0。因此， ptr2和ptr3是NULL指针 。

Program:

程序：

#include 

int main(void) {
     
	int num = 10;

	int *ptr1 = #
	int *ptr2;
	int *ptr3=0;

	if(ptr1 == 0)
		printf("ptr1: NULL\n");
	else
		printf("ptr1: NOT NULL\n");

	if(ptr2 == 0)
		printf("ptr2: NULL\n");
	else
		printf("ptr2: NOT NULL\n");

	if(ptr3 == 0)
		printf("ptr3: NULL\n");
	else
		printf("ptr3: NOT NULL\n");

	return 0;
}

Output

输出量

ptr1: NOT NULL 
ptr2: NULL 
ptr3: NULL 

翻译自: https://www.includehelp.com/c-programs/an-example-of-null-pointer-in-c.aspx

c语言指针示例