What Is C and Why It Still Matters

Where C lives

C is a small, fast, close-to-the-machine language. It powers operating-system kernels (Linux, Windows kernels), embedded firmware, database engines, and the runtimes of languages like Python and Java. Learning C teaches you how the machine actually behaves — memory, addresses, and exact types.

Compiled, not interpreted

You write source code (a .c text file). A compiler translates it into machine instructions, and a linker stitches the translated pieces plus the standard library into one executable the CPU can run directly. Nothing hides this pipeline from you in C — you will run it yourself in this course.

The smallest complete program

#include <stdio.h>

int main(void) {
    printf("Hello, C!\n");
    return 0;
}

• #include <stdio.h> — bring in the declarations for input/output (printf).
• int main(void) — every program starts here. void means it takes no parameters; the int result is a status code (0 = success).
• printf("...\n") — write text to standard output. \n is a newline.
• return 0; — report success to whoever ran the program.

Comments

/* a block comment */
// a line comment (C99 and later)

Comments are for humans; the compiler deletes them.