程序执行第一行:定义了一个int类型的变量num,由于变量num是int类型,在内存中给变量num分配4个字节的存储空间。 程序执行第二行:调用函数changeValue,此时该函数被加载进内存,函数changeValue压栈,形参声明了int类型的变量n,内存会给变量n分配4个字节的存储空间。调用changeValue传入是num变量,等价于将num存储空间的值...
[https://mp.weixin.qq.com/s/ydhK8HYuRD0lZazPsPxsvg] c/c++语言具备一个不同于其他编程语言的的特性,即支持可变参数。 例如C库中的printf,scanf等函数,都支持输入数量不定的参数。printf函数原型为 int printf(const char *format, …); printf("hello world");///< 1个参数printf("%d", a);///...
*(short*)&buf[0]=DataId;*(short*)&buf[2]=DataType;*(int*)&buf[4]=DataValue; 数据转换,利用指针的灵活的类型转换,可以用来做数据类型转换,比较常用于通讯缓冲区的填充。 指针的机制比较简单,其功能可以被集中重新实现成更抽象化的引用数据形式 函数指针,形如:#define PMYFUN (void*)(int,int),可以...
a is a constant pointer so it can not be a l_value. Array as a Function parameter The memory on the stackis used to store the address but not the whole array b.by using the address, we can change the values of element in array. #include <stdio.h> void fun(int b[])//b 存储 ...
A very useful point of pointers is that they can change more than one value. To modify the value of the main calling function through the called function, the formal parameter must be a pointer variable, and the actual parameter must be the address of the ordinary variable. Then, in the ...
is unsafe because it would allow the following valid code to attempt to change the value of the...
with no return value. After passing the value of a regular variable to a formal parameter, the value of the variable (actual parameter) remains unchanged because the function does not return a value.It can be changed to:int Change_num(int a){a =233;}int main (){int a = 123;Change_...
*(short*)&buf[0]=DataId;*(short*)&buf[2]=DataType;*(int*)&buf[4]=DataValue; 1. 数据转换,利用指针的灵活的类型转换,可以用来做数据类型转换,比较常用于通讯缓冲区的填充。 指针的机制比较简单,其功能可以被集中重新实现成更抽象化的引用数据形式 ...
/*C program to change the value of constant integer using pointers.*/#include<stdio.h>intmain(){constinta=10;//declare and assign constant integerint*p;//declare integer pointerp=&a;//assign address into pointer pprintf("Before changing - value of a:%d",a);//assign value using...
To address this issue, change reference types either to a pointer or a value. Changing the type to a pointer requires changes in the code that uses the union field. Changing the code to a value would change the data stored in the union, which affects other fields since fields in union ...