In this post I’m gonna discuss what constants are actually in C. You can access my C programming full course in order to learn programming skills quickly.
When we talk about Constants in C, there are lots of questions arise, which I will try to answer in this post.
So lets start discussing all the questions.
Contents
What are Constants in C?
C Constants are the most fundamental and essential part of the C programming language.
Constants in C are values or variables which can’t be changed in the program, also called literals.
I mean contants are like variables, which value never changes during execution once defined.
For example: 40, 54, ‘d’, 2.4, “c programming tutorial” etc. are constants.
Types of Constant in C
C Constant can be classified as:
- Integer constant
- Real constant
- Character constant
- String constant
1. Integer Constant in C Language:
Integer Constants in C are refers to the sequence of digits. Range of integer constants is -32,768 to 32,767.
There are three types of integer constants in the C language:
Decimal constant (base 10)
Decimal Digits: 0 1 2 3 4 5 6 7 8 9
Example: 0. -8, 24 etc.
Octal constant (base 8)
Octal Digits: 0 1 2 3 4 5 6 7
Example: 421, 027, 233 etc.
Hexadecimal constant (base 16)
Hexadecimal Digits: 0 1 2 3 4 5 6 7 8 9 A B C D E F
Example: 0x3f, 0x5a, 0x541 etc.
2. Real Constant in C Language
Real constant in C refers to the numbers containing fractional parts like 45.25, are called real or floating points constant. The range of Real Constants is -3.4*1038 to 3.4*1038.
There are two form of writing Real constants:
Decimal Form: -2.0, 0.0000234
Exponential Form: -0.22E-5
3. Character Constant in C Language
Character Constant in C refers to the single character enclosed within a pair of single quote (‘ ‘) like ‘A”https://dheeraj-patidar.blogspot.com/2022/08/,”d”https://dheeraj-patidar.blogspot.com/2022/08/,”54″https://dheeraj-patidar.blogspot.com/2022/08/,”8’.
The range of Character Constants is -128 to 127.
4. String Constant in C Language
String constants in c refers to the sequence of characters enclosed in double quotes, and they may include letters, digits, special characters, and blank spaces.
Examples:
“Hello”, “1987”, “?….!”, “x”, ” “, “” (null string constant)
Two ways to define constant in C
Now, we see, How to use Constants in a C Program?
There are two ways to define constant in C programming
- const keyword
- #define preprocessor
1. C const keyword
In order to define constant in C programming, the const keyword is used.
Syntax:
const type constant_name;
Lets understand declaration of constant using const keyword in C with example:
#include<stdio.h>
int main(){
const float PI=3.14;
printf(“The value of PI is: %f“,PI);
return 0;
}
Output:
The value of PI is: 3.140000
Now, If we try to change the the value of PI constant, it will throw the compile time error. How? see:
#include<stdio.h>
int main(){
const float PI=3.14;
PI=4.5;
printf(“The value of PI is: %f“,PI);
return 0;
}
Output:
Compile Time Error: Cannot modify a const object
2. C #define preprocessor
The another approach of defining constant in C is #define preprocessor.
Syntax:
#define token value
Let’s see an example of #define to define a constant in C:
#include <stdio.h>
#define PI 3.14
main() {
printf(“%f“,PI);
}
Output:
3.140000
Conclusion of Constants in C
So we have learnt What are Constants in C, Types of Constants, and 2 ways to define constants in C.
I hope you have got clear about Constants in C.
If you have any doubt about C Constants then please ask me with comment.
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