CSI 1390: Introduction to Computers

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CSI 1390 Introduction to Computers

• TA Tapu Kumar GhoseOffice STE 5014
• Email tghos009_at_uottawa.ca

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Create Folders and text files

• Creating folder
• Navigate to the directory where the folder is to
  be created
• Click right button of the mouse
• Point the mouse over the New item of the menu
• Click on the Folder option of the sub-menu
• Give a name to the newly created folder
• Press F2 to rename the folder name

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Create Folders and text files

• Creating text file using notepad
• Click the start menu presented at the
  bottom-left corner of the window
• Point the mouse over the All Programs item
• Point the mouse over the Accessories item of
  the sub-menu
• Click on the Notepad application of the
  sub-menu
• Click on the File from the menu bar of the
  notepad
• Using the Save in drop down list, navigate to
  the directory/folder where the text file is to be
  saved or created
• Give a name to the newly created text file by
  entering a name in the File name box.
• Click Save to save the file
• By default the extension of the file is .txt
• Press F2 to rename the file name

4
Using command promt to access the folders

• Click the start menu presented at the
  bottom-left corner of the window
• Point the mouse over the All Programs item
• Point the mouse over the Accessories item of
  the sub-menu
• Click on the Command Promt to open the command
  promt
• The above three steps can be done by clicking
  Run from the start menu and entering cmd in
  the text box.
• Suppose we want to access the Program Files
  folder of the C directory.
• We can do so by entering as follows
• cd\
• cd Program Files (going into the Program Files
  folder)
• dir (viewing the content of the folder)
• Now, using the above procedure go to the folder
  that you created

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First Program Hello World

• Open a notepad to write a java program that will
  display Hello World as output.
• The program is as follows
• class myProgram
• public static void main (String args)
• System.out.println(Hello world.)
• The bin directory of java is located at
  C\Program Files\Java\jdk1.5.0_12\bin
• Save the file into the above directory by giving
  the file name same as the class name of the java
  program that we wrote
• Here, the file name will be myProgram.java.
  Note that the file extension is java.
• To make the file as a java file, choose All
  files from the Save as Types drop down box at
  the time of saving. Failure to do will make the
  file as a normal text file with .txt extension.

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Compile and run the program

• The bin directory of java is located at
  C\Program Files\Java\jdk1.5.0_12\bin
• Go to the above directory by using command promt
  by using the following steps
• Open command promt and enter the following
  commands
• cd\
• cd Program Files\Java\jdk1.5.0_12\bin
• To compile the java program enter the following
  command
• javac myProgram.java
• To run the java program enter the following
  command
• java myProgram

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Explanation of the source code

• class myProgram
• public static void main (String args)
• System.out.println(Hello world.)
• Java program structured as a set of classes
• All Java code must be part of a class
• All classes must have a name. Here, our class
  name is myProgram
• Beginning of a class is identified by a opening
  brace
• Ending of a class is identified by a closing
  brace
• In a class there will be two things
• attributes (store some information)
• methods (perform some specific task)

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Explanation of the source code

• class myProgram
• public static void main (String args)
• System.out.println(Hello world.)
• Here we have only one method
• The name of the method is main
• main is a special name.
• All java program contains a method with the name
  main
• When any java program is run, it starts from the
  main method
• Body of each method contains set of statements
• Each statement is terminated by semi-solon ()
• Here we have only one statement which prints the
  information between the quotes.

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Taking input from user

• Write a java program that will ask user to enter
  his/her name and age. The purpose of the program
  is to display the user name and the square of
  his/her age.
• Before starting writing the source code we always
  try to determine few things
• What would be the input(s) to the program?
• What would be the output(s) to the program?
• How would we calculate the output?
• Here, the input is a string (for containing the
  name) and an integer (for containing the age).
• Outputs are string (that contains the name) and
  integer (that contains the square of the age).
• The output of age will be calculated by using the
  pow method of the Math class.

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Source code with explanation

• import java.io.
• import java.util.
• class myProgram
• public static void main(String args) throws
  IOException
• String name
• int age
• BufferedReader br new BufferedReader(new
  InputStreamReader(System.in))
• System.out.print("Enter your name ")
• name br.readLine()
• System.out.println("Your name is " name)
• System.out.print("Enter your age ")
• age Integer.parseInt(br.readLine())

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Source code with explanation

• throws IOException An exception that is thrown
  when I/O error encountered.
• public static void main(String args) throws
  IOException
• InputStreamReader works as a bridge from byte
  stream to character stream
• It reads bytes and decodes into characters
• BufferedReader reads text from character input
  stream
• BufferedReader br new BufferedReader(new
  InputStreamReader(System.in))

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Alernative sotution

• Add the following codes just before the last
  brace of the Keyboard.java file
• public static void main(String args)
• String name
• int age
• Keyboard kb new Keyboard()
• System.out.print("Enter your name ")
• name kb.readString()
• System.out.println("Your name is " name)
• System.out.print("Enter your age ")
• age kb.readInt()
• System.out.println(Math.pow(age,2)) // add
  import java.util.8 before the class definition

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Assignment

• Modify or add codes to the Keyboard.java file to
  do the following assignments.
• Take the temperature of a day from the user in
  degree Celsius and convert it into degree
  Fahrenheit by using the formula
• F 9/5 C 32
• Given the value of r and h, find the volume of a
  cylinder by using the formula
• V pi r r h (the value of pi can be
  obtained by using the Math class)
• Due before 8 am on September 28, 2007