What does it mean when it says "Periodic Digital Signal is composed of periodic composite analogue signal with infinite bandwidth with discrete frequencies" and "Non-periodic Digital Signal is composed of non-periodic composite analogue signal with infinite bandwidth with continuous frequencies"?

I understand that digital signals are composed of many composite analogue signals that form the whole digital wave. But I still have a few doubts from the above statements.

1. Periodic digital signal meant the signals are always "01010101" or "100110011001" or a fixed pattern and never will have situations like "10011101...", is this right?
2. The periodic digital signal is then composed of many composite analogue sine wave signals that are periodic. So it is like many periodic sine waves "squeezed" together to form that digital signal, is this right again?
3. Non-periodic digital signals would have no patterns such as "10011101..110001..", right?
4. If the above 3 questions are true so far, the non-periodic digital signals, like the periodic ones, are also composed of analogue sine wave signals, right? Since they are sine wave signals, they must have been periodic, isn't it? I mean the sine wave must have gone like from 0...0.005..1 then back to -1 then back up again. So it is periodic, isn't it? But why is it said that it is composed of non-periodic analogue signals?

Thanks for any help!

 

In answer to your question there is a nice slide in the following PowerPoint presentation ....

http://philadelphia-university.com/...Upload/Communication/1Communications-ch03.ppt


Slide print attached.