How are constants used in the C programming language?

There are several ways to use constants in the C programming language.

1. Character constants are characters enclosed in single quotes, for example: ‘a’, ‘b’, ‘c’. They can be assigned directly to a character variable or used for comparison operations.
2. String constants are a series of characters enclosed in double quotation marks, for example: “Hello, World!”. They can be assigned to character arrays or pointer variables.
3. Integer constants can be represented in decimal, octal, or hexadecimal form, such as 10, 012, 0xA. They can be assigned to integer variables.
4. Real number constants can be in decimal or exponential form, such as 3.14 or 1.23e-5, and can be assigned to floating-point variables.
5. Enumerating constants: defining constant values within an enum type, for example:

enum colors {RED, BLUE, GREEN};
enum colors myColor = RED;

1. Global constant: a constant defined using the #define preprocessing directive, for example:

#define PI 3.14159
float radius = 5.0;
float area = PI * radius * radius;

The above is the common usage of constants in the C language, choose the appropriate constant type for specific requirements.