Introduction to Unix (CA263) Computing With Unix By Tariq Ibn Aziz.

Introduction to Unix (CA263)

Computing With Unix

By

Tariq Ibn Aziz

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 astronomical-simulation 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, have cropped up.

– 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, 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.