A Mac uses the Option key in conjunction with other keys to produce characters such as ç or v.
I created a spreadsheet with the corresponding Option-set by typing <Option><key> for all the keys and then <Option><Shift><key> for all of them.
Some are used in three key combinations, e.g., <Option>`a = à or 1<Option><Shift>14 = 1/4.
Other useful combinations
<Option>e<aeiou> = á, …
<Option>u<aeiou> = ä, …
<Option>i<aeiou> = â, …
<Option>˜<aon> = ã, …
Windows must have an equivalent key.
Jason
[Edit] some of the combinations do not display on the forum. The 'v' in the first sentence was originally a 'check-mark', and the '1/4' in the second paragraph had the three characters mashed together like a single character.