Scalable and portable
Runs in many environments. TV set-top boxes, digital video recorders, bank ATM, phone switches, real time embedded systems, Macs, PC's,
Workstations, Servers, Crays, 12,000 CPU parallel processors.
Multiuser
Even for a one user machine, Unix provides a protected environment. Multiple logins allow private space and shared
resources.
Preemptive multitasking
Each program gets a "chunk" of system resources.
Many users and programs can run at the same time (in geek speak,
it has efficient context switching, good virtual memory, idle programs
are blocked waiting for I/O and can be paged out -- so you can do more with less resources)
Multiprocessing
Unix efficiently supports computer hardware with multiple CPUs.
Robust
Protected execution space, keeps on running. Makes it good for OLTP
and high availability applications. Failing user programs do not crash the
whole system (usually). Servers can often run for more than a year without rebooting.
Multiple types of software run on the same computer
Command line logins, text-based programs, background programs, shell scripts
Unattended programs, network daemons, cron jobs, mail filtering
Networks and the Internet; Remote Access
UNIX has many "built in" communication tools. Native networking is TCP/IP, but other protocols
possible. Remote access was designed into the system from the start (with dial-in lines, even before
the internet existed). Network services such as mail (smtp), http, ftp, usenet news, IRC, remote login,
remote X display, remote printing, are all available.
