Computers & Operating Systems
Overview
What's is a computer? Units of measurement Operating systems Unix
Computer Hardware
Central Processing Unit (CPU)– The heart and brains of a computer– The device that performs all calculations and data
manipulation in a computer
Main Memory (RAM)– The place the CPU looks for instructions and
data to process
Computer Hardware
Mass Storage (hard drive)– Holds information not immediately needed by CPU – Holds massive amounts of data
Input/Output Devices– keyboard, mouse, monitor, printer– Devices used to move information into and out of
the computer
Terminology - storage
bit– Stands for Binary Digit. – Smallest unit of storage
in a computer – A single 1 or 0
byte– 8 bits– Used to store single
characters. (Sort of)– ASCII characters
kilo- – Thousand– kilobyte ~ 1,000 bytes– Actually = 210 bytes (1,024)
mega- – Million– Megabyte ~ 1,000,000
bytes.– Actually = 220 bytes
(1,048,576). – About 350 pages of text
Terminology - storage
giga- – Billion– gigabyte ~
1,000,000,000 bytes– Actually = 230 bytes
(1,073,741,824)– About 360,000 pages of
text
tera-– Trillion– terabyte ~
1,000,000,000,000 bytes– Actually = 240 bytes
(1,099,511,627,776)– About 366 million pages
of text
Terminology - processing power
Clock speed– The rate at which a CPU performs its basic operations– CPU’s clock speed is measured in gigahertz (GHz)– Gigahertz ~ billion hertz (billion pulses per second). – 2.4 GHz CPU has a clock speed of 2,400,000,000 pulses
per second.
FLOPS– Floating point operations per second
MIPS– Millions of instructions per second
What is an operating system?
A computer program that
– Supports interaction between each user and the computer system
– Allocates computer resources, such as memory or CPU time, to other running programs
– Controls peripheral devices (disk drive, monitor, etc.)
Common operating systems
– Windows XP, Macintosh OS, & Linux
One user or many?
Most PCs are single-user machines – 1 keyboard, 1 monitor, intended for one person– They may run an OS capable of supporting
multiple users, but not the hardware Large computer systems are designed for
multiple users– Still composed of the same 4 main components,
but just made to work with many people at once– A more sophisticated OS is required
Multitasking & Timesharing
Unix is a multitasking operating system
– It can do more than one thing at a time
Uses timesharing to accomplish this
– Works on one task at a time for very short amounts of time and rapidly switches between them
Unix is also a multiuser operating system
– Allow many people to use the computer simultaneously
Components of Unix
Kernel– The master control program of the computer.
Shell– The part of Unix that interprets user commands and passes
them onto the kernel.
File System– Information stored on the computer. – Can be organized into directories.
Utilities– Unix commands
History of Unix
Designed to be portable — can be run on different computers
Began in 1969 at AT&T’s Bell Labs (a.k.a. Lucent Technologies)
Became a multi-user, multi-tasking Operating System
The original Unix was freely distributed and many different companies took it, modified it, added features and released their own versions
Versions of Unix
Over time, two main versions came to be the most popular.
– BSD (Berkeley Software Distribution)
– System V (AT&T Bell Labs)
Most other versions of Unix are based on one of these two versions.
– Solaris (Sun Microsystems)
– SCO (Santa Cruz Operation)
– HP-UX (Hewlett-Packard Unix)
Linux
Another version of Unix
Created by Linus Torvalds
– While a graduate student in Finland
– Based on Minix by Andrew Tannenbaum
Distributed freely
Made to run on virtually all computer systems
Red Hat is the most popular commercial distribution
Logging In
Why do it?
– Multi-user operating system
Needs to know who you are
User name, login ID, login, ID, etc.
– Each one is unique
– System administrators set up rules for user names
Password
– Many systems have rules about acceptable passwords
– Keep it secret, keep it safe
Logging in — How to do it
From PC labs
– Run a telnet program, such as PuTTY
You'll find it in the programs menu
– Prompted for name and password
Unix interface
Unix operates from a command prompt
(alphaR) 1:
Alphas use the EZ-Shell (created at UWM)
Exit the EZ-Shell with option 62
Various GUIs do exist for Unix
Xwindows
Created at MIT General protocol for running a GUI on Unix Handles the communication between the
terminal and the server (main computer) You also need a “windows manager” to
handle how the windows will look on your computer
Once you log on
Messages Set terminal type Shell prompt Changing your password
– passwd
Obtaining help– man [command name]
Logging out
How
– Type “exit”
– Type “logout”
Why?
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