Definition and use of constants in C language

In our life, there are things like pi （3.1415926...） And so on , This number often has a fixed value . In the process of coding ,C Language to prevent us from inadvertently changing its value , Therefore, the term constant is provided . Next, I will introduce two ways to define constants and the differences between them .

1.const Constants and their use

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       const  data type   Constant names  =  value ;
      
      
      
      

       
       
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then , If the value is modified, the compiler will report an error . as follows ,

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       #include<stdio.h>
       
       

       
       
int main(void) {
       
       
  const int a = 0;
       
       
  printf("a = %d",a);
       
       
  a = 10;
       
       
  printf("a = %d", a);
       
       

       
       
  return 0;
       
       
}
      
      
      
      

       
       
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Screenshot of error reporting ：

2.define Constants and their use

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       #define  Constant names   The number 
      
      
      
      

       
       
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then , If the value is modified, the compiler will also report an error . as follows ,

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       #include<stdio.h>
       
       

       
       
#define a 10
       
       

       
       
int main(void) {
       
       
  
       
       
  printf("a = %d", a);
       
       
  a = 20;
       
       
  printf("a = %d", a);
       
       

       
       
  return 0;
       
       
}
      
      
      
      

       
       
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3. The difference between the two

const A constant defined has to be a constant , It is essentially a variable , Just can't change its value .

and define The defined constants are identifier constants , It can be used as a constant .

for instance , Its use on array definitions ：

If use const Defined constant , Cannot be compiled ,

While using define Defined constant , Can be compiled ,

That's all for the definition and use of constants . If the content of the article is wrong , Welcome to point out , Thank you very much ~~~