Simple basics of C language

 

The basic knowledge of C language includes variables, data types, operators, control flow statements, functions, etc. Each part is explained in detail below, and corresponding cases are given.

1. Variables and data types:

   • Variables: Variables in C language are used to store data and need to be declared before being used. When declaring a variable, you need to specify its data type. For example:

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   int age; // 声明一个整型变量
   float price; // 声明一个浮点型变量
   char grade; // 声明一个字符类型变量
   

   • Data type: C language supports a variety of data types, including integer types (int, short, long), floating point types (float, double), character types (char), Boolean types (bool), enumeration types (enum), etc. . For example:

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   int x = 10;
   float y = 3.14;
   char c = 'A';
   bool isTrue = true;
   enum Color {RED, GREEN, BLUE};
   

2. operator:

   • Arithmetic operators: including addition (+), subtraction (-), multiplication (*), division (/) and remainder (%), etc. For example:

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   int a = 10;
   int b = 5;
   int sum = a + b; // 加法运算
   int difference = a - b; // 减法运算
   int product = a * b; // 乘法运算
   int quotient = a / b; // 除法运算
   int remainder = a % b; // 取余运算
   

   • Relational operator: used to compare the size relationship between two values, returning a boolean (true or false). For example:

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   int x = 10;
   int y = 5;
   bool isEqual = (x == y); // 相等运算
   bool isGreater = (x > y); // 大于运算
   bool isLess = (x < y); // 小于运算
   

   • Logical operators: Used to combine multiple conditions and return Boolean results. Including and (&&), or (||), and not (!), etc. For example:

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   bool isTrue = true;
   bool isFalse = false;
   bool result1 = isTrue && isFalse; // 与运算
   bool result2 = isTrue || isFalse; // 或运算
   bool result3 = !isTrue; // 非运算
   

3. Control flow statement:

   • Conditional Statements (if-else): Execute different blocks of code depending on whether the condition is true or false. For example:

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   int x = 10;
   if (x > 0) {
       printf("x is positive\n");
   } else if (x < 0) {
       printf("x is negative\n");
   } else {
       printf("x is zero\n");
   }
   

   • Loop statements (for, while, do-while): Repeatedly execute a block of code. For example:

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   for (int i = 0; i < 5; i++) {
       printf("i is %d\n", i);
   }
   
   int j = 0;
   while (j < 5) {
       printf("j is %d\n", j);
       j++;
   }
   
   int n = 0;
   do {
       printf("n is %d\n", n);
       n++;
   } while (n < 5);
   

4. function:

   • A function is a block of code that performs a specific function and can be called and reused multiple times by other code.
   • Functions need to be declared before they are used, and include the function name, parameter list and function body.
   • A function may or may not return a value.
   • For example:

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   int add(int a, int b) {
       return a + b;
   }
   
   int result = add(3, 4);
   printf("Result is %d\n", result);
   

These are the basic knowledge and detailed cases of C language. By learning and practicing these basic knowledge and cases, you will be able to master the basic programming ability of C language. Hope it helps you!