CONSTANTS IN C

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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:

1. By using ‘”#define”  
2. By using the keyword “const”

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

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
  

 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.

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)..

Program:

  

  #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.

Program:

  #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.

Program:

  #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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