Unix - Features

Multi-User System:

Multiple users can use one system at the same time. Each user will be having different terminals and keyboards, and yes ofcourse, with their own login userid and password to enter. There will be one host machine, whose memory and resources are used by these users. And one user's data is protected from that of other user's.

Multi-tasking:

More than one task can be executed simultaneously. Each task will be given few milliseconds to process. At a time single task will be in the system. But as the switch time is very minimal, it seems like all the tasks are running parallel.

Security:

Unix system is secure in following ways,
1. Each user is authenticated with userid and password.
2. All the files will be having read, write and execute permission. It is of owner's interest to give permission to other users on a particular file.
3. Third one is file encryption, the file will be in unreadable format when someone opens it. Yes, we can decrypt the file to read.

Portability:

The first and most important feature of Unix is it's portability. Most of the code in written in C language which makes unix, a hardware independent OS. Only bare minimal changes required to make unix adapt to the given architecture.