A single-user operating system, as the name suggests, is designed to support only one user at a time. It allows one user to have complete control over the system's resources and does not provide any built-in mechanisms for sharing resources among multiple users. Examples of single-user operating systems include MS-DOS and Windows 95/98.
A multi-user operating system, on the other hand, is designed to support multiple users simultaneously. It provides mechanisms for sharing resources such as CPU time, memory, and storage among multiple users and ensures that each user has a fair share of the available resources. Examples of multi-user operating systems include Unix/Linux, macOS, and Windows NT/2000/XP.