CODE EXAMPLE FOR EXCEL

To unhide all rows in excel

First need to select all cells: 
Press  Ctrl + A   Then use any of the following:

Method one:
Press Ctrl + Shift + 9

Method two: 
Press "ALT" + H + O + U + O // each key at a time

Method three:
Go to "Home" → "Format" → "Hide & Unhide" → "Unhide Rows"