Information Technology Reference
In-Depth Information
MVS (60's)
MULTICS (60's)
MSDOS (70's)
VMS (70's)
UNIX (70's)
VMware
WINDOWS (80's)
BSD UNIX (80's)
MACH (80's)
WINDOWS
WINDOWS
FREE
LINUX
NEXT
Mac OS
MOBILE
NT (90's)
BSD
(90's - pres)
ANDROID
Mac OSX
WINDOWS 7 (2010)
iOS
In
uence
Descendant
Figure1.11: Geneology of several modern operating systems.
The basic operation of a web server is similar to a time-sharing system. The
web server waits for a packet to arrive, requesting a web page or to perform an
action such as search the web or purchase a topic. The network hardware copies
the arriving packet into memory using DMA. Once the transfer is complete, it
signals the arrival of a packet by interrupting the processor, triggering the server
to perform the requested task. Likewise, the processor is interrupted as each
block of the web page is read from disk into memory. Like a time-sharing system,
server operating systems need to be designed to handle very large numbers of
short actions per second.
The earliest time-sharing systems supported many simultaneous users, but
even this was only a phase. Eventually, computers became cheap enough that
people could aord their own dedicated "personal" computers, which would sit
patiently unused for much of the day. Instead, access to shared data became
paramount, cementing the shift to client-server computing.
1.3.5
Modern operating systems
Today, we have vast diversity of computing devices, and many different oper-
ating systems running on those devices.
The tradeoffs faced by an operating
