Type qualifiers add special attributes to existing datatypes in C programming language.

There are three type qualifiers in C language and constant type qualifier is explained below −

Const

There are three types of constants, which are as follows −

• Literal constants

• Defined constants

• Memory constants

Literal constants − These are the unnamed constants that are used to specify data.

For example,

a=b+7 //Here ‘7’ is literal constant.

Defined constants − These constants use the preprocessor command ‘define" with #

For example, #define PI 3.1415

Memory constants − These constants use ‘C’ qualifier ‘const’, which indicates that the data cannot be changed.

The syntax is as follows −

const type identifier = value

例如，

const float pi = 3.1415

如您所见，它只是给出一个字面名称。

示例

以下是常量类型限定符的C程序：

#include<stdio.h>
#define PI 3.1415
main ( ){
   const float cpi = 3.14
   printf ("literal constant = %f",3.14);
   printf ("defined constant = %f", PI);
   printf ("memory constant = %f",cpi);
}

输出

当上述程序被执行时，它产生以下结果 −

literal constant = 3.14
defined constant = 3.1415
memory constant = 3.14