Developer TODO list:

Priority A (should be done ASAP)

	*   (nothing)

Priority B (should be done someday) 

	*   (nothing)

Priority C (may be someday)

	*   Algebraic mode: operations with constants invoked by double 
	    pressing of binary operation buttons.

	*   HEX mode. It is going to be a separate program, because of the 
    	    small overlap between the functionality required for decimal and 
    	    hexadecimal calculations. 

	*   Saving of all operations somethere; their output by demand.
