C语言中的指针和数组之间的区别？

指针用于存储动态分配的数组的地址，以及用于作为参数传递给函数的数组。在其他情况下，数组和指针是两个不同的东西，请参见以下程序以证明此语句的合理性。
sizeof运算符的行为

C++

// 1st program to show that array and pointers are different
#include 
using namespace std;
 
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
    int* ptr = arr;
 
    // sizof(int) * (number of element in arr[]) is printed
    cout << "Size of arr[] " << sizeof(arr) << "\n";
 
    // sizeof a pointer is printed which is same for all
    // type of pointers (char *, void *, etc)
    cout << "Size of ptr " << sizeof(ptr);
    return 0;
}

C

// 1st program to show that array and pointers are different
#include 
 
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
    int* ptr = arr;
 
    // sizof(int) * (number of element in arr[]) is printed
    printf("Size of arr[] %ld\n", sizeof(arr));
 
    // sizeof a pointer is printed which is same for all
    // type of pointers (char *, void *, etc)
    printf("Size of ptr %ld", sizeof(ptr));
    return 0;
}

输出

Size of arr[] 24
Size of ptr 8

不允许将任何地址分配给数组变量。

C

// IInd program to show that array and pointers are different
#include 
 
int main()
{
   int arr[] = {10, 20}, x = 10;
   int *ptr = &x; // This is fine
   arr = &x;  // Compiler Error
   return 0;
}

输出：

Compiler Error: incompatible types when assigning to 
              type 'int[2]' from type 'int *' 

有关更多差异，请参见有关此主题的上一篇文章。
尽管数组和指针是不同的东西，但是数组的以下属性使它们看起来相似。

1. 数组名称给出数组的第一个元素的地址。

例如，考虑以下程序。

C++

// 1st program to show that array and pointers are different
#include 
using namespace std;
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
 
    // Assigns address of array to ptr
    int* ptr = arr;
    cout << "Value of first element is " << *ptr;
    return 0;
}

C

#include 
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
    // Assigns address of array to ptr
    int* ptr = arr;
    printf("Value of first element is %d", *ptr);
    return 0;
}

输出

Value of first element is 10

使用指针算法访问数组成员。
编译器使用指针算法访问数组元素。例如，像“ arr [i]”这样的表达式被编译器视为*(arr + i)。这就是为什么像*(arr + i)这样的表达式适用于数组arr，而像ptr [i]这样的表达式也适用于指针ptr的原因。

C++

#include 
using namespace std;
 
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
    int* ptr = arr;
    cout << "arr[2] = " << arr[2] << "\n";
    cout << "*(arr + 2) = " << *(arr + 2) << "\n";
    cout << "ptr[2] = " << ptr[2] << "\n";
    cout << "*(ptr + 2) = " << *(ptr + 2) << "\n";
    return 0;
}

C

#include 
 
int main()
{
   int arr[] = {10, 20, 30, 40, 50, 60};
   int *ptr = arr;
   printf("arr[2] = %d\n", arr[2]);
   printf("*(arr + 2) = %d\n", *(arr + 2));
   printf("ptr[2] = %d\n", ptr[2]);
   printf("*(ptr + 2) = %d\n", *(ptr + 2));
   return 0;
}

输出

arr[2] = 30
*(arr + 2) = 30
ptr[2] = 30
*(ptr + 2) = 30

数组参数始终作为指针传递，即使我们使用方括号也是如此。

C++

#include 
using namespace std;
 
int fun(int ptr[])
{
    int x = 10;
     
    // Size of a pointer is printed
    cout << "sizeof(ptr) = "
         << (int)sizeof(*ptr)
         << endl;
 
    // This allowed because ptr is a
    // pointer, not array
    ptr = &x;
 
    cout <<"*ptr =  " << *ptr;
 
    return 0;
}
 
// Driver code
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
     
    // Size of a array is printed
    cout << "sizeof(arr) = "
         << (int)sizeof(arr)
         << endl;
          
    fun(arr);
     
    return 0;
}
 
// This code is contributed by shivanisinghss2110

C

#include 
 
int fun(int ptr[])
{
    int x = 10;
 
    // size of a pointer is printed
    printf("sizeof(ptr) = %d\n", (int)sizeof(*ptr));
 
    // This allowed because ptr is a pointer, not array
    ptr = &x;
 
    printf("*ptr = %d ", *ptr);
 
    return 0;
}
 
// Driver code
int main()
{
    int arr[] = { 10, 20, 30, 40, 50, 60 };
     
    // size of a array is printed
    printf("sizeof(arr) = %d\n", (int)sizeof(arr));
    fun(arr);
    return 0;
}

输出

sizeof(arr) = 24
sizeof(ptr) = 4
*ptr = 10 

有关更多详细信息，请参考C语言中的Pointer vs Array。

想要从精选的最佳视频中学习和练习问题，请查看《基础知识到高级C的C基础课程》。