This article provides developers familiar with C language with key points to quickly get started with C. 1. Classes and objects: C's class is an upgrade of the C structure, supports encapsulating data and methods, and introduces access control characters private and public. 2. Constructor and destructor: implement automatic object initialization and resource release. The constructor has no return type. It is recommended to use an initialization list. 3. STL: The standard template library provides efficient containers such as vector, map, and set, simplifying common data structure operations. 4. Namespace and input and output: Use cin/cout instead of scanf/printf to avoid name conflicts through namespace. Mastering these core contents can create practical C programs.

If you are already familiar with C language and want to get started with C quickly, then this article will directly focus on the key points. C is not a completely independent new language. It developed on the basis of C, so you already have a good starting point. However, C has introduced many new concepts and mechanisms, such as classes, objects, templates, STLs, etc., which require you to gradually adapt.

The following starts from several key points to help you convert the basics of C into the ability to write C code.

Class and Object: Upgraded version of C structure

In C, we use struct to organize the data. In C, class is an enhanced version of struct . In addition to encapsulating data, it can also include functions (methods).

 class Rectangle {
private:
    int width, height;
public:
    void set(int w, int h) {
        width = w;
        height = h;
    }
    int area() {
        return width * height;
    }
};

You can use this class like this:

 Rectangle r;
r.set(3, 4);
cout << r.area(); // Output 12

Some points to note:

• private and public are access control characters that can protect internal data from being modified by external arbitrarily.
• C allows functions to be defined in classes, which cannot be done in C.
• The default access permission of the class is private , while the default access permission of struct is public , which is one difference between the two.

Constructors and destructors: Automatically executed initialization and cleaning

In C, initializing a structure usually requires manually calling a function, such as init_rect() . C provides constructors that allow you to automatically complete initialization when creating objects.

 class Rectangle {
public:
    Rectangle(int w, int h) : width(w), height(h) {
        cout << "Initialized";
    }
    ~Rectangle() {
        cout << "Destroyed";
    }
private:
    int width, height;
};

• The constructor has no return type, and the name is the same as the class name.
• Using initialization lists ( : width(w), height(h) ) is more efficient and is recommended.
• The destructor is used to free resources and is automatically called at the end of the object's life cycle.

STL: Standard template library, making container operation easier

C programmers often implement linked lists, queues and other structures themselves. The C standard library provides powerful container classes, such as vector , map , set , etc., which are not only efficient, but also reduce the possibility of errors.

For example, use vector instead of dynamic arrays:

 #include <vector>
using namespace std;

vector<int> nums;
nums.push_back(10); // Add element for (int n: nums) {
    cout << n << endl;
}

Common containers are:

• vector : dynamic array, suitable for sequential access
• map : key-value pair storage, suitable for search
• set : Automatically sorted collection to avoid duplication

suggestion:

• Familiar with iterators and range-based for loops
• Use algorithm libraries (such as sort , find ) instead of writing loops yourself

Namespace and input and output: say goodbye to printf and embrace iostream

C has its own input and output methods, such as cin and cout , which are safer and easier to scale than scanf and printf .

 #include <iostream>
using namespace std;

cout << "Hello, world!" << endl;
int x;
cin >> x;

In addition, namespace can help you organize your code and avoid name conflicts:

 namespace math {
    int add(int a, int b) {
        return ab;
    }
}

math::add(2, 3); // Call method

Basically that's it. C has many advanced features, such as templates, inheritance, polymorphism, smart pointers, etc., but if you already have the foundation of C, you can first master the above content and write a practical C program. There is no need to pursue the plenary session from the beginning, and it is better to learn while writing.

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