constants in c language

C programming language mein constants, unchanging values hote hain jo program ke various parts mein istemal kiye jaate hain. Constants, variables ke opposite hote hain, kyunki unki values program ke execution ke dauraan change nahi hoti. C language mein do prakar ke constants hote hain:

1. **Literals (Literal Constants):** Literals constant values hote hain jo code mein directly define kiye jaate hain. C language mein kuch prakar ke literals hote hain:

- **Integer Literals:** Integer literals whole numbers ko represent karte hain. For example, `5`, `-10`, `1000`.

- **Floating-Point Literals:** Floating-point literals decimal numbers ko represent karte hain. For example, `3.14`, `-0.005`, `1.0`.

- **Character Literals:** Character literals ek character ko single quotes (`'`) ke bheetar represent karte hain. For example, `'A'`, `'5'`, `'%'`.

- **String Literals:** String literals multiple characters ko double quotes (`"`) ke bheetar represent karte hain. For example, `"Hello, World!"`, `"C Programming"`.

- **Boolean Literals:** C language mein boolean literals as such nahi hote hain, lekin 0 ko `false` aur kisi bhi non-zero value ko `true` ke roop mein interpret kiya ja sakta hai.

Example:

```c int x = 5; // Integer Literal

float pi = 3.14; // Floating-Point Literal

char grade = 'A'; // Character Literal

char name[] = "John"; // String Literal

``` 2. **Symbolic Constants (Symbolic Constants ya Macros):** Symbolic constants program ke readability aur maintainability ko improve karne ke liye istemal hote hain. Inhe preprocessor directives jaise `#define` ke dwara define kiya jata hai aur unhe ek specific value se associate kiya jata hai. Aap symbolic constants ka istemal kisi fixed value ko multiple locations par change kiye bina kar sakte hain.

Example:

```c

#include

#define PI 3.14159265

int main() {

float radius = 5.0;

float area = PI * radius * radius;

printf("Area of the circle: %f\n", area);

return 0;

}

```

Is example mein `PI` ek symbolic constant hai jiska value `3.14159265` hai aur ise program ke multiple parts mein use kiya ja raha hai.

Symbolic constants ka istemal program ke maintenance ko aasan banata hai,

kyunki agar future mein aapko value ko badalna ho to aapko sirf ek hi jagah par value ko update karna hota hai.