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?