OneonOne allows you to compare one folder or volume with another. It is most useful if you desire to have one folder mirror another. There are four listing fields. The two fields above each other on the left are finders. You use the 'Choose Folder' button in each case to select your starting folder/volume. If you choose a large hard disk to start you may have memory problems. You can also drag and drop a folder on each of the windows.
Once you have selected the folders you can further navigate in the usual manner. On a pc closed folders will be marked by a + sign while on a Mac they will be marked by a triangle tag. You expand the folder by clicking on the symbol as usual. When you arrive at the folder you wish to investigate, double click it and its structure will be displayed in the field on the right. Do this for both folders on the left and you get the structure of each on the right. Memory shown for folders is the sum total of all the included files in it and its subfolders.
Next use the examine button. If the folders are identical, that is, if all the folders/files have the same name, memory use and creation date, you will be so notified. If they are not not identical, another window will open with a report of all differences and you will be given the means to adjust these differences to bring the folders to the same state.