1. Introduction to C Programming

Why Learn C?

C is the language of systems programming. Understanding C gives you insight into how computers actually work at the memory and processor level. Many modern languages — including C++, Java, Python, and Rust — draw concepts from C.

• Operating Systems — Linux, Windows, and macOS kernels are written primarily in C
• Embedded Systems — Microcontrollers and IoT devices run C code
• Performance — C produces fast, efficient machine code
• Foundation — Learning C makes you a better programmer in all languages

Your First C Program

The tradition in C programming is to start with a program that prints Hello, World! to the screen. This demonstrates the basic structure of a C program.

The #include directive tells the preprocessor to include the standard input/output library. The main() function is the entry point of every C program. printf() outputs text to the console, and return 0 indicates successful execution.

Compilation Stages

C code goes through four distinct stages before becoming an executable program:

• Preprocessing — Handles directives like #include and #define, expanding macros and including header files
• Compilation — Converts the preprocessed code into assembly language specific to your CPU
• Assembly — Converts assembly code into machine code (object files)
• Linking — Combines object files with libraries to create the final executable

You can stop at any stage using compiler flags. For example, gcc -E stops after preprocessing, and gcc -S stops after compilation.

Compiling and Running

To compile a C program, you need a C compiler. The most common compiler is GCC (GNU Compiler Collection).

If you don't specify an output name with -o, GCC creates a file named a.out by default. On Windows, the executable will have a .exe extension.