C in 100 Seconds: Three Files One Program — Header Files | Episode 16

Header files separate declarations from definitions. The .h file declares what exists — function signatures. The .c file defines how they work. #ifndef guards prevent double inclusion. Three files: a header with two function declarations, an implementation with the bodies, and a main that calls them. Include with quotes for your files, angle brackets for system libraries. Compile both .c files and the linker connects the calls to the implementations. That's how real C projects are organized. Student code: https://github.com/GoCelesteAI/c-in-100-seconds/tree/main/episode16 What You'll Learn: • .h files declare, .c files define • #ifndef / #define / #endif — include guards • #include "quotes" for your files, brackets for system • Compiling multiple .c files together • The linker connects calls to implementations Phase 1 Complete! Next: Episode 17 — Pointers (Phase 2: Pointers and Memory) #c #programming #100seconds #learnc #headerfiles #ifndef #include #multifile #linker #tutorial Tags c header files, ifndef c, include c, multi file c, declaration vs definition, include guards, linker c, c tutorial 2026, c beginner, 100 seconds, learn c, coding tutorial