Single-user on-line systems...

- allows for interaction between user and job, to influence future processing.

Examples : Using a microcomputer for 

• playing a computer game; 
• word-processing;

Multi-user On-line systems (Multi-access systems)

- allow a number of users to access a central computer interactively. (Careful...this is not the same as a network.)

The operating system scans all the on-line terminals in turn to see if there are any requests.

If there is, the user is given a time-slice of processing time. These time slices are so small that a user's 'turn' comes round very quickly and it seems to the user that he is the only one using the computer. When the user enters a command the response time will be small - there will be little delay in having his command processed.

Example : students in a college using terminals to run software on a central computer.