For a long time, I have opened the Image Size window and have changed the sizes of my images in inches. When I open the Image Size, the default measurement was always in inches. I am aware that one can change the measurements in the drop-down menu next to the size, but that is not what I wish to do, as that is an extra step that has not been necessary for years. What I do not understand is that today the default document size measurements changed to centimeters and not inches. This is driving me crazy! How do I change the default measurements back to inches instead of centimeters without having to change cm to inches every time I open an image in the Image Size window?
The Image Size window edits your current document unit and does not apply this globally. If you look carefully there is also a "percent" option on the size. So is not posible to display an image in percent units. To change Photoshop's unit globally, that is for each and every document you open, the solution is https://graphicdesign.stackexchange.com/a/86472/88258
This issue can be solved by going to "Units & Rulers" under Preferences (Cmd+K) within Photoshop CS5. However, what became the issue was having a document open, using the ruler on the document (Cmd+R), and ctrl+clicking the ruler of the document and then changing those measurements from inches to pixels. Upon doing that, you will notice that any images opened in the Image Size window have centimeters selected on the drop-down settings. Of course, you can change those settings as well, but it can be a pain if you have more than one photo. So, if you are finding that this is a problem for you, ctrl+click the ruler in the document again and reselect inches. Then you will find that the default measurement in the Image Size window is back to inches. You can also go to Preferences (Cmd+K), but I wanted to post this answer because some people might not link the Image Size changes to the changes they made by using the ruler.