Introduction to Unix (CA263)
Computing With Unix
Objectives
• After reading this chapter, you should be
able to:
– Discuss the background and philosophy
underlying the use of computers
– Overview of basics of computer hardware and
software
– Explain why you are learning about Unix
– Illustrate features and advantages of using
the Unix operating system.
Computer Basics
• What is a computer?
– A tool that helps and make impossible task easy, it
helps in solving mathematical problems
• Why do we need computers?
– Without computers many tasks require countless
hours of hand calculation
• How do we use them?
– Never trust computer’s output. Always check your
input, otherwise garbage in, garbage out. To check
results use pencil-and-paper analysis.
History of Computing
• Webster dictionary defines computer as “a
programmable electronic device that can
store, retrieve, and process data.”
• Computer technology improved rapidly in
late 19th and 20th century.
• Invention of the electronic computer chip
began the microcomputer revolution in
1970s.
Computer Classifications
• Computers are generally classified into
three categories: supercomputers,
mainframes and workstations.
– Supercomputers handles complicated
problems in high-level engineering and
scientific enterprises.
– Mainframe computers supply services for
many users in industry. (e.g. Airline industry)
– Powerful, stand-alone personal computers
are called workstations.
Computer Components and Usage
• Computer Hardware:
– Five components classify computer
hardware: the processor, memory, and
devices for input, output, and storage.
1. Input devices: Keyboards, mice, scanner etc.
2. Processor: CPU is the brain of computer and it
interprets instruction entered by input device.
Computer Components and Usage
3.Memory: Internal memory usually split between
RAM and ROM. RAM is for reading and writing
information required by program. ROM store
permanent information.
4.Storage: Floppy disks, CD-ROM, HDD to store
electronic information. Program stored on these
can be loaded into Memory.
5.Output: The most common output device is the
video display terminal (VDT) or monitor. Another
form of output is hard copy, such as printouts on
paper.
Computer Components and Usage
• Computer Software
– Without program CPU is nothing. CPU need
knowledge or instructions to process input
and produce useful output.
– Although computers are not intelligent,
software teach computer hardware, what to
do
Computer Components and Usage
• Bit and Bytes
– Computer store information with the digit 0
and 1 – binary digit, or just bit
– Bit is the smallest component of memory
– A group eight bits make 1 byte.
– megs and gigs refer to big chunk of memory
Computer Components and Usage
• Programs
– Computer programs are instructions written
in a programming language that CPU
understands.
– Computer programs that perform word
processing, financial analysis are called
application software or just applications.
– Programs designed to help people to use
computers and applications are called
system software (operating systems)
Computer Components and Usage
• Operating System
– CPU uses operating systems to control all
computer functions.
– When you turn on OS loaded into the
memory.
– The OS controls who applications transfer
data between main memory and output.
Computer Components and Usage
• Graphical User Interface
– Originally, computer had unfriendly interface,
such as monochrome monitors and teletype
machines.
– GUI (goo-ees) software presents an interface
of pull-down menus and point-and-click
mouse operations inside windows.
– GUIs tend to avoid text-based command entry
in order to provide friendly environment
Unix Operating System
• History of Unix
• Unix Variants
• Why Unix?
History of Unix
• Unix was born in 1969 in Bell Labs as a better
way to run Space Travel, an astronomicalsimulation program
• Ken Thompson, a Unix developer got frustrated
with running Space Travel on Multics
(Multiplexed information and computing system)
computer.
• In 1973 after many revision in Assembly code,
Ken Thompson and Dennis Ritchie rewrote Unix
in C language just for that task.
• Eventually AT&T the owner of Bell Labs,
released Unix to educational institution, but
without any support.
Unix Variants
– Since source code of Unix was publicly available,
different versions, both commercially and
free,
– Linux is freely available, Mac computer has
Unix operating system.
– If you prefer not to install a new operating
system, you might try cygwin
(www.cygwin.com) , which is Linux emulator.
Cygwin provide a Unix like environment that
run on top of Microsoft windows.
Why Unix?
– Remember GUI environment is not an OS
– GUI just hide OS command from user
– Experienced user get tired of GUI very soon
– Why are we having keyboard shortcuts, just
to improve efficiency
– Text-based command improve efficiency
– Originally Unix was developed for computers
with limited memory, so we use “cp” instead
of “copy” every character counted.
Why Unix?
• Unix has many advantages to offer:
– Openness, source code is publicly available
– Utilities, variety of commercial software available
– Portability, every kind of computer supports Unix
– Multiuser, Unix can handle many users running
different programs
– Multitasking, A user can run different program
simultaneously
– Networking, Unix allows computers to connect
and share information, in fact Unix protocols
forms the basis of the Internet
– Prevalence, Workstations that employ Unix help
solve many complicated engineering and science
problems
Windows Systems and Other
Operating Systems
• Microsoft windows or Macintosh operating
systems are GUI based
• Although Unix is taught as a text-based
OS, many types of GUI based Unix are
also available, including X windows,
(CDE) Common Desktop Environment,
and others.
Unix Basic
•
•
•
•
Software layers
File System
Utilities
Unix GUIs
Software layers
• Many kinds of layers are available between the
user and the computer hardware in Unix.
• The outer most layer, the shell, read and interpret
your command.
• Not all Unix use the same shells, some commands
even differ from shell to shell.
• Utilities and program can be called by the shell to
do some task.
• The resident modules perform input/output and
process control.
• The kernel, directs the hardware to perform your
commands.
File System
• Common task such as report writing,
programming, and analysis, generate
electronic information that files store.
• Files are stored in directories.
Directories are arranged in
hierarchical structure often known as
a directory tree.
Utilities
• After you become familiar with
Unix, you may wish to write
programs called shell scripts,
which perform customized task
that you devise.
Unix GUIs
• Unix is primarily text based, but GUIs are
available for it.
• The X Windows system developed by
Xerox Park is a common Unix-based
window system.
• A group of computer companies has
produced the Common Desktop
Environment that is now very popular.