In computing and document management, these terms differ from each other by the method used for storing and retrieving the information:
Hard Copy: A physical copy or version of a document that is usually in the form of a paper document. Once the document is printed on a computer or any device, the information stands on its own without any connection to the computer or device.
Soft Copy: A digital version or copy of a document that is usually on a computer or any device. It is not a physical copy or version of a document.
Photo Copy: A special type of hard copy that is usually created by scanning a document that is already in hard copy or paper format and then printing it on a paper document using a photocopier.
Ditto Copy: This is another term for a copy that was usually created by a spirit duplicator, a device that was used in most schools before the advent of computer printers or photocopiers.