Hello World

My First Program (1)

hello.c #include <stdio.h> int main(void) { printf("hello, world\n"); return 0; } Build and execute $ gcc hello.c $ ./a.out hello, world

What we see … A program consists of functions and variables Functions consist of statements Function call (printf()) is a statement main() is special (int return value ⟶ OS Exit Status) Building appears simple but isn’t stdio.h??

My First Program (2)

#include <stdio.h>	Declarations from the Standard IO Library Here: for printf()
int main(void)	Definition of main() Required for a program Entry point from the C runtime
{ printf("hello, world\n"); }	Body of main() Calling printf() with a string parameter/argument. \n is the newline character

Character Arrays - Strings

Strings are special in C

• Character: …

• String: zero terminated character array

• Escape sequences, e.g. \n (newline), \t (tabulator), \", \0 (null)

The string "hello,world\n" corresponds to …