"C Language Elementary" Chapter 2 - Getting to Know C Language (2)

Getting to Know C Language Part 2

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select statement

If you study hard, you will find a good offer. If you don't study hard, go home and sell sweet potatoes. This is the select statement.

选择语句类型：

• Single branch: if statement, else statement;
• Multi-branch: if elseif else statement, switch case statement;

If the expression in the if evaluates to true, the if statement is executed, otherwise the else statement is executed.

Here I use ifto achieve:

#include<stdio.h>
int main()
{
    
    
	int i = 0;
	printf("今天你学习了吗？1 or 0\n");
	scanf("%d", &i);
	if (i == 1)
		printf("good offer!\n");
	else
		printf("回家卖红薯！\n");
	return 0;
}

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loop statement

A loop statement means doing the same job repeatedly
循环语句类型:

• for statement
• while statement
• do while statement

The three looping statements have their own advantages in different scenarios.
Example:
Xiao Ming is determined to learn an algorithm question every day, and when he writes a hundred questions, he will post a circle of friends

#include<stdio.h>
int main()
{
    
    
	int count = 0;
	while (count<100)
	{
    
    
		count++;
	}
	printf("%d\n发朋友圈", count);
	return 0;
}

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function

The function is 可以实现某种功能的模块
the function of the function: it is used to simplify the code, realize the reuse of the code, and realize the specific function eg: calculator
Example: realize the function of addition

#include<stdio.h>
int sum(int x, int y)
{
    
    
	return x + y;
}
int main()
{
    
    
	int a = 0, b = 0, c = 0;
	printf("please input two members:>");
	scanf("%d%d", &a, &b);
	c = sum(a, b);
	printf("c=%d\n", c);
	return 0;
}

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array

Array: is used to store a set of elements of the same type

array definition

int arr[10]={
    
    1,2,3,4,5,6,7,8,9,10};

subscript of the array

Each element of the array has a subscript, and the subscript 从0开始can be used to locate its corresponding value

If we want to get the fifth element in the array, we can do this

int arr[10]={
    
    1,2,3,4,5,6,7,8,9,10};
printf("%d\n",arr[4]);

print array

#include<stdio.h>
int main()
{
    
    
	int arr[10] = {
    
     1,2,3,4,5,6,7,8,9,10 };
	int i = 0;
	for (i = 0; i < 10; i++)
	{
    
    
		printf("%d ", arr[i]);
	}
	return 0;
}

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operator

• Arithmetic operators
  +, -, *, /, %

• Shift operators
  << (left shift), >> (right shift)

• Bitwise operators
  & (bitwise and), | (bitwise or), ^ (bitwise exclusive or)

• Assignment operator
  = += -= *= /= &= ^= |= >>= <<=

• unary operator
  

• relational operator
  

• Logical Operators
  && Logical And
  || Logical Or

• Conditional operator
  exp1?exp2:exp3

• comma expression
  exp1,exp2,exp3,...expN

• Subscript reference, function call and structure member variable access operators
  [], (), ., ->

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common keywords

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define constants and macros

//define定义标识符常量
#define MAX 1000
//define定义宏
#define ADD(x, y) ((x)+(y))
#include <stdio.h>
int main()
{
    
    
    int sum = ADD(2, 3);
    printf("sum = %d\n", sum);

    sum = 10 * ADD(2, 3);
    printf("sum = %d\n", sum);

    return 0;
}

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pointer

Variables are created in memory (space is allocated in memory), and each memory unit has an address, so variables also have addresses.
Save the address of a variable into a new variable, this new variable is called指针变量

structure

Structures can describe complex types in C language, such as students: name + age + gender + student number, but using a single type to describe requires many types of definitions, while structures can:

//结构体类型的定义
struct Stu
{
    
    
    char name[20];//名字
    int age;      //年龄
    char sex[5];  //性别
    char id[15]； //学号
};

So far, the first knowledge of C language is over. In the next article, I will continue to share each knowledge point in detail and look forward to the next issue~~