Unix
A common operating system in host computers on the Internet. (See host.)

Uploading
Sending files to another computer. (See downloading.)

URL - Uniform Resource Locator
A set format for displaying a Web page address on the Internet, for example:  http://www.geo.co.il  . (See http, Web page.)

Usenet- the User Network
This system developed at the same time as ARPANET. It allows for discussions between various users via a computer network. (See newsgroups, ARPANET.)

Userid
The name a user uses to identify himself/herself when logging in to his/her computer. (See login.)

Username
See userid.

UUcode
Software that converts binary files (non-text files) into ASCII files (text-only files) so that they can be transferred over the Internet by electronic mail, which can only transfer text files. (See ASCII, E-Mail, Text, UUdecode.)

UUdecode
Software that translates files that underwent the UUcode process back into binary files. (See ASCII, UUcode.)