Pointers are a key tool for efficient memory operation in C. 1. A pointer is a variable that stores memory addresses, and accesses the target value by dereference (); 2. Common operations include address fetching (&), dereference () and pointer operation (such as p); 3. When using dynamic memory, you need to cooperate with new and delete/delete[] to avoid memory leakage, repeated release and wild pointers; 4. Pointers can be used as function parameters to realize external variable modification and array transfer; it is recommended to practice more to understand its essence, and combine smart pointers to improve security.

Pointers are a basic but critical concept in C. Mastering it well is very helpful for writing efficient and flexible code. Many people will feel that the pointer is a bit wiggled at first, but in fact, as long as you understand the essence, it is not difficult to use.

What is a pointer?

Simply put, a pointer is a variable that stores the memory address . We usually use pointers to indirectly access or modify the value of a variable. for example:

 int a = 10;
int* ptr = &a;

Here ptr is a pointer to type int , which holds the address of variable a . The value of a can be accessed through *ptr .

A common misunderstanding is to understand pointers and ordinary variables together. In fact, there is a "indirect layer" between them, so pay special attention to this.

Basic operation of pointers

When using pointers, there are three most commonly used operations: address fetching, dereference, and pointer arithmetic.

• Get the address (&) : Get the memory address of the variable.
• * Dereference ( )**: Access the content pointed to by the pointer.
• Pointer operation : For example, adding one to the pointer will jump to the next corresponding data position.

For example:

 int arr[] = {1, 2, 3};
int* p = arr; // Point to the first element of the array cout << *p; // Output 1
p ;
cout << *p; // Output 2

This is very useful when iterating through arrays or processing strings.

What should be noted is:

• Do not dereference uninitialized pointers
• Avoid accessing freed memory
• Remember delete after using dynamic allocated memory

The relationship between dynamic memory and pointer

C allows us to manually apply memory at runtime, which requires the use of pointers to match new and delete :

 int* num = new int(5); // Dynamically allocate an int
delete num; // Remember to release int* arr = new int[10]; // Assign an array delete[] arr; // Note that you should use delete[]

This part of the error-prone areas includes:

• Forgot to free memory causes memory leak
• Release the same piece of memory multiple times
• Continue to use pointers (wild pointers) after release

It is recommended to use smart pointers (such as std::unique_ptr or std::shared_ptr ) to automatically manage memory and reduce the chance of errors.

Pointer and function parameters

Sometimes we hope that the function can modify the variable passed in, and at this time we can use a pointer as a parameter to pass the address:

 void increment(int* val) {
    (*val) ;
}

int a = 5;
increment(&a);

This method saves more resources than passing values ??and allows functions to affect external data.

In addition, pointers can also be used to pass arrays to functions:

 void printArray(int* arr, int size) {
    for (int i = 0; i < size; i)
        cout << arr[i] << " ";
}

The advantage of writing this way is that the function does not need to know the specific size of the array, it only needs to know the pointer and length.

Basically that's it. The pointer looks complicated, but in fact the core is address and indirect access. You can get started by practicing it a few more times.

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