C++ Basics

Here’s a C++ study note that covers some of the basics and important points of C++:

I. C++ Basics

1. Basic data types

• Integer:
  • ‘int’: typically 32 bits, storing integers, e.g. 'int num = 10; `。
  • ‘long’:一般为 64 位,存储较大范围的整数,如 ‘long bigNum = 123456789012345L;’。
  • ‘short’: typically 16 bits, suitable for storing a smaller range of integers, 'short smallNum = 32767; `。
• Floating-point:
  • ‘float’: single-precision floating-point number, low precision, stores numbers with decimals, 'float pi = 3.14f; `。
  • double：双精度浮点数，精度更高，是常用的浮点数类型，double moreAccuratePi = 3.141592653589793;。
• Character Type:
  • char：存储单个字符，如 char letter = 'A';。
  • ‘string’:存储字符串,需要包含 ‘’ 头文件,‘string name = “John”;’。

2. Variables and constants

-Variable:
- When defining a variable, you need to specify the data type, and then you can assign and modify the variable, for example:
cpp int age; age = 25; age = age + 1;
- It can also be initialized directly at definition time: 'int score = 85; `。
-Constant:
- The ‘const’ keyword can define constants, and the value of the constant cannot be modified after initialization, such as:
cpp const int MAX_VALUE = 100;
- You can also use ‘#define’ to define constants, but it’s not recommended because it’s a preprocessor instruction and not type-safe:
cpp #define PI 3.14159

3. operator

• Arithmetic Operators:
  • Include ‘+’ (add), ‘-’ (minus), ‘*’ (multiply), ‘/’ (divide), ‘%’ (remainder), etc., e.g.:

  int result = 10 + 5; 
  int remainder = 10 % 3; 
  

• Relational Operators:
  • For example, ‘>’ (greater than), ‘<’ (less than), ‘==’ (equal to), ‘!=’ (not equal to), ‘>=’ (greater than or equal to), ‘<=’ (less than or equal to), which are often used for conditional judgment:

  if (score > 80) {
       
       
      cout << "优秀" << endl;
  }
  

• Logical Operators:
  • ‘&&’ (logical and), ‘||’(logical or), ‘!’ (logical not), used to combine multiple conditions, such as:

  if (score >= 60 && score < 80) {
       
       
      cout << "及格" << endl;
  }
  

Second, control flow

1. Conditional statements

• if-else 语句：

  if (condition) {
       
       
      Executed when the condition is true
  } else {
       
       
      Executed when the condition is false
  }
  

  For example:

  if (age >= 18) {
       
       
      cout << "成年"