what are the differences between an original keyboard and a modern version?

Do you mean by "original" keyboard? A typewriter?
~

The original keyboard had a tinny voice and fewer small keys. Then after there was the piano which was easier to avoid hitting wrong keys and had a full voice big enough to fill larger halls. The keyboards of today have buttons and sliders and switches to do everything from change digital instrument voice and varying pitch to creating loop-backs and changing pre-set beats.

As there are never been a standard for what keys on are a keyboard (beyond the qwerty layouts of the keys), it is difficult to compare them and to know why each of the thousands of keyboard makers decided to use they layout that they did.

However if you are talking about the original keyboard for the IBM-PC and IBM-XT, both included two rows of "F" keys. Besides the F1-F12 found on most (not all) keyboards, there was a second row numbered F13-F24. There might also have been a small keypad section with several commands used on mainframe computers.

IBM was the inventor of the main frame computer, and that was still 99% of the business when the PC was introduced. Since there were no mice, icons, menus or point and click on main frames, everything was done by pressing a key. They required more keys to handle all the functions of a main frame.

The first PCs also lacked mice, icons, menus, etc. So they were also given keyboards with more function keys in anticipation of the programs that would need that many keys.

However with the coming of Windows (and other graphic interfaces) the need for those keys was reduced, and so was the number of keys. On many computers today even the F1-F12 keys serve little to no function.

sounds like you want me to do your homework :))