Writing C Hello world Programs

• A programmer uses a text editor to create or modify files containing C code.
• Code is also known as source code.
• A file containing source code is called a source file.
• After a C source file has been created, the programmer must invoke the C compiler before the program can be executed (run).

#include <stdio.h>

/* The simplest C Program */

int main(int argc, char **argv)
{

  printf("Hello World\n");

  return 0;

}

/*

OUTPUT:
Hello World

*/

• The main() function is always where your program starts running.
• #include inserts another file. “.h” files are called “header” files. They contain stuff needed to interface to libraries and code in other “.c” files.
• This is a comment. The compiler ignores this.
• Blocks of code (“lexical scopes”) are marked by { … }
• Print out a message. ‘\n’ means “new line”.
• Return ‘0’ from this function