====== Lab01 - Introduction to the Computer Laboratory and C Programming Language ======
 
  * Introduction to the computer environment - password settings
  * Introduction to the working environment - terminal control and elementary commands: ''ls'', ''cd'', ''pwd'', ''mkdir'', ''cp'', ''mv'', ''rm'', ''touch'', and ''man'', ''cat'', ''find'', ''grep'', ''wget'', ''unzip'', ''echo'', and input/output modificators: ''|'', ''>'', ''>>''.
  * Compile the first program
  * Test the executed program
  * Become familiar with your selected favorite editor for editing sources, e.g., gedit, Sublime Text, Emacs, Vim. 

   
   
===== Lab Code =====

**Exercise 1**

Simple program to output text:

<code>
#include <stdio.h>

int main()
{
    //this line is a comment, it will be ignored
    printf("Hello World!");
    return 0;
}
</code>

Practice compiling it:
<code>gcc myprogram.c</code>

Gcc will take your code and produce a binary executable from it.
See if you can figure out:

How to customise your executable filename from gcc.
Make it format correctly in the terminal.



**Exercise 2**

We can use printf("here is an integer: %i", myint); to format an integer.
Similarly %f to format a float.

We can use scanf("%f", &fnum); to get a variable from the command line user.

Implement a function that calculates the euclidean distance of two numbers.
That is, it takes two numbers, squares each of them, adds them, and returns the square root.


==== Basic terminal programs Help ====

Open terminal Ctrl + Alt + T
New tab Ctrl + Shift + T
End programs by running Ctrl+C
Close by Ctrl + D

=== man ===

Manual to (almost) every terminal program can be found using ''man'':
  $ man <program>
You shoud start working in linux terminal by asking, how to use manual
  $ man man

=== pwd ===

To find out, where are you in the directory tree, the present working directory, use ''pwd'':
  $ pwd


=== ls ===

To list files in your directory, use ''ls'':
  $ ls
There is also possibility to see a content of different directory
  $ ls <relative/absolute address>
The useful parameters you should know are:
  * ''-a'' do not ignore entries starting with ., usualy hidden files,
  * ''-A'' the same as ''-a'' but it does not list implied . and ..,
  * ''-l'' uses a long listing format,
  * ''-p'' to append / at the end of the name of directories to differentiate them from files,
  * you can also sort them by ''-S'' size, ''-t'' time, etc.,
  * and combine them

  $ ls -Al


=== cd ===

To change the directory use ''cd'':
  $ cd <relative/absolute address>
Go to the parent directory
  $ cd ..
Go to the parent's parent directory
  $ cd ../../
Go to the parent's parent directory and then to its child directory
  $ cd ../../some_directory/
Go to the child's child directory
  $ some_directory/some_subdirectory/
You can use absolute address:
  $ /home/my_account/my_files/my_video/
There is also trivial way to your home directory:
  $ cd
The manual is not presented, therefore use parameter ''--help'' to find out more
  $ cd --help
For fast navigation, use keypad **Tab**. Use it frequently.


=== mkdir and touch ===

If you want to create a directory, use ''mkdir'':
  $ mkdir <directory name>
and ''touch'' for file creation:
  $ touch <file name>
Please, do not use spaces in your names:
  $ mkdir "I have come here from some advertising environment called Windows"
  $ mkdir and\ I\ really\ like\ to\ troll
and if necessary, use ''_'' underscore instead:
  $ touch I_love_linux 


=== mv ===

Use ''mv'' for moving files or directories from one position in a directory tree to another: 
  $ mv <source> <destination>
  $ mv random_file.txt ~/random_directory/
  $ mv random_directory/ ~/some_directory/some_subdirectory/
Note that character ''~'' stands for your //home directory//.

Use ''mv'' also for renaming the files:
  $ mv obsolete_name much_better_name

=== cp ===

Copying files can be done using ''cp'':
  $ cp <source> <destination>
  $ cp random_file.txt ~/random_directory/
  $ cp random_file.txt ~/random_directory/better_name.txt
To copy whole directory, use ''-r'' //recursive// option:
  $ cp -r random_directory/ ~/other_directory/some_subdirectory/


=== rm ===

You can delete file using ''rm''
  $ rm <file name>
Beware! It is very hard to //undo//!

Deleting whole directory and its content needs ''-r'' //recursive// option:
  $ rm -r obsolete_directory/
It is also possible to delete file (or directory) at different position in directory tree:
  $ rm ~/random_directory/random_file.txt
  $ rm ../../some_system_directory/some_essential_file