C Variable Names (Identifiers)

1. What is an Identifier?

• An identifier is a name given to variables, functions, arrays, or any user-defined item in C.

• It is used to identify and refer to memory locations where data is stored.

Example:

2. Rules for Naming Variables (Identifiers)

1. Start with a letter or underscore (_):

   int age; // valid
int _count; // valid
int 1num; // invalid (cannot start with a number)


2. Can contain letters, digits, and underscores:

   int age1; // valid
int _total2; // valid


3. Cannot be a C keyword (reserved word):

   int int; // invalid
int return; // invalid


4. Case-sensitive:

   int age; // different from 'Age'
int Age; // different from 'AGE'


5. No special characters or spaces allowed:

   int my-age; // invalid
int my age; // invalid


3. Best Practices for Variable Names

1. Use meaningful names:

   int age; // good
int a; // not descriptive


2. Use camelCase or snake_case for multi-word names:

   int studentAge; // camelCase
int student_age; // snake_case


3. Avoid single letters unless in loops:

   int i; // okay for loop index


4. Keep names short but readable.

4. Examples of Valid Identifiers

5. Examples of Invalid Identifiers

6. Example Program Using Identifiers

Output:

✅ Key Takeaways:

• Always follow the rules for identifiers.

• Use meaningful names for clarity.

• C is case-sensitive, so be consistent.