For all those who type ‘sl’ instead of ‘ls’ often in the command window: Get the program ‘sl’
sudo apt-get install sl
From its man page:
sl – display animations aimed to correct users who accidentally enter sl instead of ls.
It rarely shows contents of current directory.
When going through the source code for sl, I saw the use of the curses library. Its new implementation ncurses describes itself as “CRT screen handling and optimization package.”
The library is very useful. All the old Turbo C cursor functions, mouse functions, getch() and much more is implemented in this. 
 Avoid common mistakes: a) Read up on the function refresh(). b) When compiling in gcc, use the option -lcurses option.