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A Brief History of UNIX
by Sam Coniglio
Contract Technical Writer
Email: spaceman@mindspring.com
September 07, 1999
In the beginning, there was AT&T.
Bell Labs’ Ken Thompson developed UNIX in 1969 so he could play games on a
scavenged DEC PDP-7. With the help of Dennis Ritchie, the inventor of the “C”
programing language, Ken rewrote UNIX entirely in “C” so that it could be used
on different computers. In 1974, the OS was licensed to universities for educational
purposes. Over the years, hundreds of people added and improved upon the system, and it
spread into the commercial world. Dozens of different UNIX “flavors” appeared,
each with unique qualities, yet still having enough similarities to the original AT&T
version. All of the “flavors” were based on either AT&T’s System V or
Berkeley System Distribution (BSD) UNIX, or a hybrid of both. During the late 1980’s
there were several of commercial implementations of UNIX:
- Apple Computer’s A/UX
- AT&T’s System V Release 3
- Digital Equipment Corporation’s Ultrix and OSF/1 (renamed to DEC UNIX)
- Hewlett Packard’s HP-UX
- IBM’s AIX
- Lynx’s Real-Time UNIX
- NeXT’s NeXTStep
- Santa Cruz Operation’s SCO UNIX
- Silicon Graphics’ IRIX
- SUN Microsystems’ SUN OS and Solaris
... and dozens more.
The Open Standards Foundation is a UNIX industry organization designed to keep the various
UNIX flavors working together. They created operating systems guidelines called POSIX to
encourage inter-operability of applications from one flavor of UNIX to another.
Portability of applications to different gave UNIX a distinct advantage over its mainframe
competition.
Then came the GUIs. Apple’s Macintosh operating system and Microsoft’s
Windows operating environment simplified computing tasks, and made computers more
appealing to a larger number of users. UNIX wizards enjoyed the power of the command line
interface, but acknowledged the difficult learning curve for new users. The Athena Project
at MIT developed the X Windows Graphical User Interface for UNIX computers. Also known as
the X11 environment, corporations developed their own “flavors” of the UNIX GUIs
based on X11. Eventually, a GUI standard called Motif was generally accepted by the
corporations and academia.
During the late 1990’s Microsoft’s Windows NT operating system started
encroaching into traditional UNIX businesses such as banking and high-end graphics.
Although not as reliable as UNIX, NT became popular because of the lower learning curve
and its similarities to Windows 95 and 98. Many traditional UNIX companies, such as DEC
and Silicon Graphics, abandoned their OS for NT. Others, such as SUN, focused their
efforts on niche markets, such as the Internet.
Linus Torvalds had a dream. He wanted to create the coolest operating system in the
world that was free for anyone to use and modify. Based on an obscure UNIX flavor called
MINIX, Linus took the source code and created his own flavor, called Linux. Using the
power of the Internet, he distributed copies of his OS all over the world, and fellow
programmers improved upon his work. In 1999, with a dozen versions of the OS and many GUIs
to choose from, Linux is causing a UNIX revival. Knowing that people are used to the
Windows tools, Linux developers are making applications that combine the best of Windows
with the best of UNIX.
A Brief OS Comparison
It would be impossible to create a complete comparison of commands without creating a
book, so here are a few examples. I compare some common UNIX commands with MS-DOS, MS
Windows and Apple Macintosh. All of the OSs have similar functions, but implement them
slightly differently.
UNIX and MS-DOS
At first glance, the UNIX command line looks a lot like MS-DOS command line. In fact,
some of the commands are the same. Then subtle differences appear. The DOS prompt looks
like C:\ while the UNIX prompt looks like “$” or “#” The slashes are
different: DOS uses the backslash “\” while UNIX uses the forward slash “/
”. Finally, for each UNIX command, there are a ton of switches to customize the
output of the command.
| To ... |
UNIX |
MS-DOS |
| display list of files |
ls OR ls -l |
dir/w dir |
| display contents of file |
cat |
type |
| display file with pauses |
more |
type <filename> | more |
| copy file |
cp |
copy |
| find string in file |
grep OR fgrep |
find |
| compare files |
diff |
comp |
| rename file |
mv |
rename OR ren |
| delete file |
rm |
erase OR del |
| delete directory |
rmdir |
rmdir OR rd |
| change file protection |
chmod |
attrib |
| create directory |
mkdir |
mkdir OR md |
| change working directory |
cd |
chdir OR cd |
| get help |
man OR apropos |
help |
| display date and time |
date |
date, time |
| display free disk space |
df |
chkdsk |
| print file |
lpr |
print |
| display print queue |
lpq |
print |
| kill a crashed program |
kill |
UNIX and Windows
With the advent of Microsoft Windows, many of the DOS command line functions became
abstract. Document icons represent files and folder icons represent directories. But
Windows is still glued to its command line past. Just click on the “Start”
button, select the “Run” command, type cmd in the text field, click the
OK button, and poof!! Good old DOS command line appears in a new window.
| To ... |
UNIX |
Microsoft Windows |
| display list of files |
ls OR ls -l |
Double-click on My Computer, or activate Windows Explorer. In View menu choose
“Details” |
| display contents of file |
cat |
Double-click on an icon |
| display file with pauses |
more |
Click on the scroll arrows |
| copy file |
cp |
Select Icon, choose Copy from Edit menu, or from right mouse menu |
| find string in file |
grep OR fgrep |
Not in OS, but third party tools available |
| compare files |
diff |
Not in OS but third party products available |
| rename file |
mv |
Click on file’s name, or choose Rename from right mouse menu |
| delete file |
rm |
Selec t icon and press Delete key |
| delete directory |
rmdir |
Select icon and press Delete key |
| change file protection |
chmod |
Select icon, choose Properties from right mouse menu, click on Read-only checkbox |
| create directory |
mkdir |
Choose New->Folder from the File menu |
| change working directory |
cd |
Double-click on a folder icon |
| get help |
man OR apropos |
Select Help menu |
| display date and time |
date |
Date and time displayed on task bar |
| display free disk space |
df |
Click on disk icon, and capacity pie chart appears (Win98 Explorer mode) or space
available displays in info bar (Windows Explorer) |
| print file |
lpr |
Ctrl-p (most programs) |
| display print queue |
lpq |
Double-click on printer icon on task bar |
| kill a crashed program |
kill |
Ctrl-Alt-Del, select application from list, click End Task button |
UNIX and Macintosh
Apple’s Macintosh operating system was designed from the ground up as graphical
OS. There are no command line shells like MS Windows. This make life easy for people new
to computers, but it can be frustrating for DOS and UNIX experts. With the upcoming MacOS
X, a Macintosh/UNIX hybrid, Apple may satisfy both new computer users and command line
wizards.
| To ... |
UNIX |
Macintosh |
| display list of files |
ls OR ls -l |
Double-click on a folder or disk icon. In View menu choose “as List” |
| display contents of file |
cat |
Double-click on an icon |
| display file with pauses |
more |
Click on the scroll arrows |
| copy file |
cp |
Select Icon and press command-D |
| find string in file |
grep OR fgrep |
Command-F activates “Sherlock” tool, select “Find by Content” tab |
| compare files |
diff |
Not in OS but third party products available |
| rename file |
mv |
Click on file’s name |
| delete file |
rm |
Click and drag icon to trash, or command-delete |
| delete directory |
rmdir |
Click and drag icon to trash, or command-delete |
| change file protection |
chmod |
Get Info on a file, click on lock button |
| create directory |
mkdir |
Command-N |
| change working directory |
cd |
Double-click on a folder icon |
| get help |
man OR apropos |
Select Help menu, or command-? |
| display date and time |
date |
Date and time displayed on menu bar |
| display free disk space |
df |
Free space listed on top of each window |
| print file |
lpr |
Command-P |
| display print queue |
lpq |
Double-click on printer icon on desktop |
| kill a crashed program |
kill |
Command-Option-Esc |
Web Sites for Reference
Here are some useful UNIX-related web sites. The Web has thousands more.
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