C Preprocessor and Macros

C Preprocessor and Macros

The C Preprocessor and Macros runs before the actual compilation of the program.
It processes instructions beginning with the # symbol, called preprocessor directives.

These directives help include files, define constants, create macros, and control compilation.

📌 Common Preprocessor Directives

1️⃣ #include Directive

Used to insert the contents of another file.

2️⃣ #define (Macros and Constants)

✔ Define a constant:

✔ Define a macro function:

👀 Warning: Macro without parentheses can cause errors:

❌ Wrong:

✔ Correct:

3️⃣ #undef

Removes a defined macro.

4️⃣ Conditional Compilation

Used when compiling different environments (debug mode, Windows/Linux, etc.)

#ifdef Example:

#ifndef Example:

✔ #if / #elif / #else

5️⃣ Multi-line Macros

Use \ to continue on the next line:

6️⃣ Predefined Macros

C provides built-in macros:

Example:

 Advantages of Macros

✔ Faster execution (no function call)
✔ Easy constant management
✔ Useful in debugging
✔ Platform-specific compilation

 Disadvantages

❌ Can cause unexpected behavior
❌ Hard to debug
❌ No type checking

🧠 Summary