What are the three basic structures in C language?

The three basic structures in C language programs are: 1. Sequential structure, which refers to execution in program order; 2. Selection structure, which refers to selecting the branch direction based on the judgment result; 3. Loop structure, which refers to a loop Body, you can decide how many times to loop based on the judgment conditions.

#The operating environment of this article: Windows 7 system, Dell G3 computer, C11 version.

There are three types of program structures in C language: sequential structure, selection structure, and loop structure. Next, in the article, we will introduce the usage of these three basic structures in detail, which has a certain reference effect. I hope it will be helpful to everyone.

In C language programs There are three program structures: sequential structure, selection structure (branch structure), and loop structure

Sequential structure:

The sequential structure is one sentence after another from beginning to end. Execute it until the last sentence is executed. As shown below

Example: Enter an uppercase letter from the keyboard and request to use lowercase letters instead

#include<stdio.h>
int main()
{
  char x,y;  
  scanf("%c",&x); 
if(x >= &#39;A&#39; && x <= &#39;Z&#39;)
    { 
        y=x+32;
    }    
    else
    {
        printf("this is a erro"); 
    }
 printf("%c\n",y);
 return 0;
}

Select structure

After arriving at a certain node, the branch direction to be executed will be determined based on the result of a judgment. As shown in the figure below

Example: Enter three numbers, and then arrange them from small to large

#include<stdio.h>

int main()
{
    float a,b,c,tmp;
   
    scanf("%f %f %f",&a,&b,&c);
    if(a > b)
    {
        tmp=b;
        b=a;
        a=tmp;
    }
    if(a > c)
    {
        tmp=c;
        c=a;
        a=tmp;
    }          
    if(b > c)
    {
        tmp=c;
        c=b;
        b=tmp;
    }             
    printf("%5.2f %5.2f %5.2f\n",a,b,c);
    return 0;
}

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Loop structure

The loop structure has a loop body , the loop body is a piece of code. For loop structures, the key is to decide how many times to execute the loop body based on the judgment result;

Example: Calculate 1 2 3 ···· 10

#include <stdio.h>

int main(void)
{
  int i, sum;
   printf("i = %d.\n", sum); 
    for (i=0,sum=0; i<=10; i++)
    {
        sum += i;
    }
    printf("sum = %d.\n", sum); 
    return 0;
}

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