c语言指针示例 |
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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 |
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