Exercise Hello-World

1. Get yourself an account on IFA computer system. You probably have one if you have an email account on phys.au.dk;
2. Boot your POSIX system e.g. from the Ubuntu CD;
3. Prepare the directory for the exercises:
   • Open a terminal window (in Gnome: Applications→Accessories→Terminal) and login into lifa.phys.au.dk (or, better, kecdac if you are inside IFA's firewall). If your login name is fedorov (it is not), do

     
     ssh -X fedorov@lifa.phys.au.dk
     

     where -X option is needed if you plan to use X-windows programs. After typing your password do

     
     mkdir ~/public_html
     mkdir ~/public_html/numeric
             

     where ~/ is an abbreviation for you home directory. Now the URL http://www.phys.au.dk/~fedorov points to your ~/public_html/ directory, while http://www.phys.au.dk/~fedorov/numeric points to your"~/public_html/numeric" directory which should then be the place for your solutions to the exercises.
   • Remember to do

     
     chmod -R go+xr ~/public_html
     

     to allow everybody to see your files in this directory. You might need to issue this command again after you have created some new files.
4. Pick your favourite programming language for the exercises. The only restriction is that there should be a debian package for it (i'll be surprised if there isn't). For example, Javascript -- is an easy to learn modern language built in every browser (though not really used for scientific programming); C -- it's probably the most ubiquitous language in existence, it is very fast and powerful and and there is GNU Scientific Library written in C.
5. Pick your favourite editor to edit your programs. If you don't have one, try the following editors available on lifa and kecdac: nano (very simple), jed (more advanced), gedit (simple graphical interface, you probably want this one), emacs (popular with computer programmers), vi (good old stuff from 1976, still going strong), kate (KDE advanced text editor)...
6. Create a Hello-World program in your favourite programming language with your favourite editor and build it using make utility. In C:
   
   • mkdir ~/public_html/numeric/hello
   • cd ~/public_html/numeric/hello
   • create a file hello.c with the content

     
     #include <stdio.h>
     int main() {
     	printf("Hello, world\n");
     	return 0;
     }
     

   • create a file makefile with the content

     
     hello.txt: hello       # hello.txt is the default target
     	./hello > hello.txt # run hello and redirect stdout into hello.txt
     	cat hello.txt       # send the content of hello.txt to stdout
     
     hello: hello.o
     	cc hello.o -o hello
     
     clean:
     	rm -f hello hello.o hello.txt
     	

     Note that the indented lines start with a tab-character, not with spaces.
   • Now run the make utility

      make 

     you should see the message on your screen if everything goes right (it never does the first time, of course...).
   • You can find other hello-world examples here. Note that some compilers are only installed on kecdac, not lifa.
7. Send me an email with the URL of your exercises, when you are done.