Windmilling Project

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BIL101E
UNIX OPERATING SYSTEM- Review Labwork
-PROGRAMMINGAlgorithms and Programs
Turgut YilmazOffice 244E-mail
turgut.yilmaz_at_itu.edu.trwww.mkn.itu.edu.tr/yilma
ztur
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Operating Systems Overview

• Review of UNIX Commands
• Lab work - Unix

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Review of UNIX Commands
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UNIX Commands Starting and Ending
Logging in Enter your username password t
o login to the system. If login successfully,
you will see Unix Prompt
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UNIX Commands Starting and Ending
telnet Connecting to another machine e.g. telne
t hyperion.labs.itu.edu.tr telnet
mecheng.strath.ac.uk telnet atlas.cc.itu.edu.tr
When connected, it will ask your username and
password
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UNIX Commands Starting and Ending
Logging out when you have finished, you must log
out exit or logout
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UNIX Commands File Management
vi or pico or Emacs or joe To edit text
files mkdir Creating a directory cd
Changing your current working directory ls
Finding out what files you have cp Making a
copy of a file mv Changing the name of a
file rm Getting rid of unwanted
files chmod Controlling access to your
files cmp or diff Comparing two files wc
Word, line, and character count
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UNIX Commands To Get Help
To get help man commandname To get
help man ls man man
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UNIX Commands Files
Use help option man to find out what these
commands are for
tail chmod file spell diff
pg cat touch head
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UNIX Commands Communication
pine Using Pine to send and receive
e-mail talk Talk to another user write
Write messages to another user ftp
Transferring files with ftp telnet Connecting
to another computer
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UNIX Commands To Get Help
To get help man -k keyword e.g. man -k
print
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UNIX Commands Information
man Manual pages quota -v Finding out your
available disk space quota df and du Info about
disk usage finger Getting information about a
user passwd Changing your password who
Finding out who's logged on
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UNIX Comments Printing
lp or lpr Printing cancel or lprm Removing a
print job
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UNIX Commands Job Control
ps Finding your processes kill Killing a
process nohup Continuing a job after
logout nice Changing the priority of a
job To run a background process
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From Algorithms to Programs
Algorithm and Flowchart Programming and
Programming Languages
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Software Development
Understand the problem
Come up with an algorithm
Implement it in a program
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Algorithm A methodical approach to solve a
problem
Example The algorithm to compute the average of
N Numbers is to add them up and then divide by N
Flowcharts are used to describe algorithms
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What is a program?
A Program is a precise expression of an
algorithm in a language that could be followed
by a computer
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More About Algorithms

• An algorithm is made up of a set of basic steps
• that are followed sequentially.
• Each algorithm must have a single entry point.
• Each algorithm must have one or more
  exit/finish points

Flowcharts are for us to visualize the algorithm
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More About Algorithms

• Example

Problem You are given 100 or more numbers
written on a card and asked to find the
highest number.
Algorithm Go through the cards (one at a time)
and remember the highest you have encountered
so far.
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More About Algorithms

• Another Example

Problem You are given a list of 100 or more
numbers. SORT them in a descending order.
Algorithm - Find the largest number by going
through the list - Find the second largest in
the remaining list - Find the 3rd largest in
the remaining list - ... - Until the
remaining list is empty.
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Flowchart Sorting a List of Numbers
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Flowchart Symbols and Their Meanings
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Programming and Programming Languages

• Programs are precise instructions expressed in
  a programming languages.
• The only language computer can follow are low
  level machine instructions.
• Writing machine language programs are difficult
  and most of the time not necessary.

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Computer Languages

• Low Level languages
• - Difficult to learn and use
• - Examples include machine and assembly
  languages
• High Level languages
• - English-like vocabulary
• - Examples include C, Fortran, Pascal, Java,
  Cobol etc.

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Interpreters and Compilers
To translate a program into machine language
requires translator software.
Interpreters each instruction is translated
individually when needed during execution
Compilers The entire program is translated into
machine language before execution
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Into the Computer

• A high-level program needs to be written using
  text editor.
• Once typed into the text editor, it can be saved
  to disk.
• To run the program, it must be translated into
  machine language
• by means of an interpreter or compiler.

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Edit-Compile-Execute cycle
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Programming Approaches

• Structured Programming
• A technique used to make programming easier.
• Many small programs are written and then
  combined.
• Object-oriented programming
• The program is a collection of interactive
  objects that
• contain both data and instructions.
• Visual Programming
• Programmers write programs by drawing pictures
  and
• pointing to objects on the screen.

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1st Midterm Exam !

• Possibly 13 March 2003
• Online exam, 2 stages
• 1st stage 40 questions in 20 minutes
• YES, NO, NO ANSWER type of questions
• 70 weighting
• 2nd stage 10 questions in 10 minutes
• filling in empty spaces
• 30 weighting
• Timing exam ends when you press TAMAM
• or when the time is up.
• 3 wrong answers cancel 1 correct answer
• 5 No answers cancel 1 correct answer
• Questions are from chapters 1, 2, 3 and 4