Constants In C
Constants in C are basically defined as a named memory. In constants are
values that are fixed and cannot be altered during program
execution.
Constants are used to represent fixed values in a program, such as numerical values, character values, or boolean values. The constants in C programming can be of any data type: a character type, floating type, string, integer, and double type.
Constants in C using two methods:
- By using ‘”#define”
- By using the keyword “const”
Example: #define program
#include<stdio.h>
//define constant variable
#define PI 3.15
int main()
{
float area;
int radius
=5;
area= PI * radius*radius;
printf("Area
= %f\n",area);
}
Output:
Area=78.750000
Example:const keyword Program
#include<stdio.h>
//using const keyword to PI value
const float PI=3.15;
int main()
{
float area;
int radius
=5;
area= PI * radius*radius;
printf("Area = %f\n",area);
}
Output:
Area=78.750000
Syntax:
const data_type variable_name= value;
#define variable_name value
Types of C Constants:
1. Integer constants
2. Real or Floating point constants
3. Octal & Hexadecimal constants
4. Character constants
5. String constants
2. Real or Floating point constants
3. Octal & Hexadecimal constants
4. Character constants
5. String constants
Integer Constants in C:
- An integer constant must have at least one digit.
- It must not have a decimal point.
- It can either be positive or negative.
Example: The common ways to represent integer constants in C Program
#include <stdio.h>
int main() {
// Decimal constant using const keyword
const
int decimalConstant = 23;
printf("Decimal constant: %d\n", decimalConstant);
// Octal constant using const keyword
const
int octalConstant = 052;
// 52 in decimal
printf("Octal constant: %d\n", octalConstant);
// Hexadecimal constant using const keyword
const
int hexConstant = 0x2A; // 42 in decimal
printf("Hexadecimal constant: %d\n", hexConstant);
// Binary constant using const keyword (C99 and later)
const int binaryConstant =
0b101010; // 42 in decimal
printf("Binary constant: %d\n", binaryConstant);
// Long integer constant using const keyword
const long int longConstant
= 123456789L;
printf("Long integer constant: %ld\n", longConstant);
// Unsigned integer constant using const keyword
const unsigned int unsignedConstant = 42U;
printf("Unsigned integer constant: %u\n", unsignedConstant);
return 0;
}
Output:
Decimal constant: 23
Octal constant: 42
Hexadecimal constant: 42
Binary constant: 42
Long integer constant: 123456789
Unsigned integer constant: 42
Real Constants in C:
1.Floating-Point Values:
- Real constants in C represent floating-point values, which include float and double types.
2.Notation:
- Real constants can be written in decimal, like 3.14 or 2.71828.
- Exponential notation is also valid, e.g., 2.5e-3 (2.5 times 10 to the power of -3) or 1.23e4 (1.23 times 10 to the power of 4)..
Example: Decimal Notation & Exponential Notation
#include <stdio.h>
int main() {
// Decimal Notation with const keyword
const float constFloatVar =
3.14f;
const double constDoubleVar
= 2.71828;
printf("Decimal Notation with const keyword:\n");
printf("Float: %f\n", constFloatVar);
printf("Double: %lf\n", constDoubleVar);
// Exponential Notation with const keyword
const float constScientificFloat = 2.5e-3f;
const double constScientificDouble
= 1.23e4;
printf("\nExponential Notation with const keyword:\n");
printf("Scientific Float: %e\n", constScientificFloat);
printf("Scientific Double: %e\n", constScientificDouble);
return 0;
}
Output:
Decimal Notation with const keyword:
Float: 3.140000
Double: 2.718280
Exponential Notation with const keyword:
Scientific Float: 2.500000e-03
Scientific Double: 1.230000e+04
Character Constants in C:
- A character constant is a single character, a single digit or a single special symbol enclosed within single quotes.
- The maximum length of a character constant is 1 character.
Example: char constant
#include <stdio.h>
int main() {
const char charVar =
'A';
// Constant character
const char escapeVar =
'\n'; // Constant character using escape sequence
printf("Character Constant: %c\n", charVar);
printf("Escape Sequence: %cHello\n", escapeVar);
return 0;
}
Output:
Character Constant: A
Escape Sequence:
Hello
String Constants in C:
These are constants that represent a sequence of characters enclosed within
double quotes.
Example:
#include <stdio.h>
int main() {
// String Constants
const char greeting[] =
"Hello";
const char sentence[] =
"This is a string.";
// Printing String Constants
printf("Greeting: %s\n", greeting);
printf("Sentence: %s\n", sentence);
return 0;
}
Output:
Greeting: Hello
Sentence: This is a string.
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