Introduction to Unix (CA263) Computing With Unix

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Introduction to Unix (CA263) Computing With Unix

• By
• Tariq Ibn Aziz

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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.

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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 computers output. Always check your
  input, otherwise garbage in, garbage out. To
  check results use pencil-and-paper analysis.

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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.

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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.

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Computer Components and Usage

• Computer Hardware
• Five components classify computer hardware the
  processor, memory, and devices for input, output,
  and storage.
• Input devices Keyboards, mice, scanner etc.
• Processor CPU is the brain of computer and it
  interprets instruction entered by input device.

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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.

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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

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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

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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)

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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.

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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

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Unix Operating System

• History of Unix
• Unix Variants
• Why Unix?

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History of Unix

• Unix was born in 1969 in Bell Labs as a better
  way to run Space Travel, an astronomical-simulati
  on 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 ATT the owner of Bell Labs, released
  Unix to educational institution, but without any
  support.

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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.

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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.

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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

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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.

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Unix Basic

• Software layers
• File System
• Utilities
• Unix GUIs

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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.

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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.

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Utilities

• After you become familiar with Unix, you may wish
  to write programs called shell scripts, which
  perform customized task that you devise.

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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.