| Word | Description |
| ODBC (open database connectivity) | An internationally agreed standard for interfacing with and accessing databases. |
| Online | Any activity carried out on a computer whilst connected to an Intranet or the Internet. |
| Online purchasing | Ordering and paying for items online, usually by providing credit card details. |
| Open system | A system that is capable of communicating with other open systems through common international standard protocols. |
| Operating system | The program installed on a computer that manages all the other programs or applications that run on the computer. Unix, Mac OS, Windows XP, Windows 98, and Windows NT are some examples of operating systems. |
| OSI (open systems interconnection) | The seven-layer industry-standard reference model, which has been applied extensively to the client/server architecture. |
| Outsourcing | Contracting work to another company. |