Variables

•	A variable is data name that may be used to store a data value.
–	Variable names correspond to locations in the computer's memory
–	Every variable has a name, a type, a size and a value
–	Whenever a new value is placed into a variable, it replaces (and destroys) the previous value
–	Reading variables from memory does not change them

Key Concepts of Variables in C:

1.Declaration

o	Before using a variable, you must declare it by specifying its type and giving it a name.
o	Syntax: type variable_name;

2.Data Types: C has several data types, and the type of a variable determines the kind of value it can store.
    Common data types in C:

o	int: Integer type, stores whole numbers (e.g., int a = 5;)
o	float: Floating-point type, stores numbers with decimal points (e.g., float b = 3.14;)
o	double: Double precision floating-point type, for larger or more precise floating-point numbers (e.g., double pi = 3.14159;)
o	char: Character type, stores individual characters (e.g., char c = 'A';)
        You can also use other types like long, short, unsigned, and long long to
        modify the size and range of variables.

3.Initialization: A variable can be initialized (assigned an initial value) when it is declared.

o	Syntax: type variable_name = initial_value; char grade = 'A';      // 'grade' is initialized to 'A'

4.Variable Naming Rules:

o	Variable names must begin with a letter (a-z, A-Z) or an underscore (_).
o	After the first character, you can use letters, digits (0-9), or underscores.
o	Variable names are case-sensitive (age and Age are different).
o	A variable name cannot be a C keyword (e.g., int, return, if).

5.Scope and Lifetime of Variables:

o	The scope of a variable refers to the region of code where the variable can be accessed.
o	The lifetime refers to how long the variable exists in memory.
        There are different types of variables based on scope:
o	Local variables: Declared inside a function and accessible only within that function.
o	Global variables: Declared outside of any function, and accessible by any function in the program.
o	Static variables: Retain their value between function calls.
o	Dynamic variables: Variables that are created and managed at runtime using functions like malloc.

6.Example Program: Here's a simple program that declares, initializes, and uses variables:

   #include < stdio.h>
 
   int main(){
      int a = 5;        
            float b = 4.5;   
         char c = 'X';     

            printf("Integer value: %d\n", a);                    
            printf("Float value: %.2f\n", b);
                  printf("Character value: %c\n", c);

    return 0;
}
Output:
Integer value: 5
Float value: 4.50
Character value: X
Variable Types in Detail:
•	Integer Types:
o	int: A standard integer.
o	short: A short integer, typically smaller in size than int.
o	long: A long integer, typically larger in size than int.
o	long long: An extended size integer.
o	unsigned int, unsigned short, etc.: Unsigned versions of integer types (no negative values).
•	Floating-Point Types:
o	float: Single precision floating-point type.
o	double: Double precision floating-point type.
o	long double: Extended precision floating-point type.
•	Character Type:
o	char: Stores a single character.