CS 111 - 9/4/14

tshell2@uic.edu

Follow Lab schedule as shown in
  http://www.cs.uic.edu/~grad/2014FallTA.pdf

Labs on Mondays
  - Lab Quiz occurs first
  - TA will present the weekly lab assignment
  - Work on lab assignment & ask questions of TA

Prof. Troy's office hours are planning to run from
  11am to 2pm on Friday 9/5

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Variable - hold information for the program to use

   The information is stored in the computers RAM
      memory while the program is executing

We create variables and give them identifier names

   All identifiers must first start with a letter
      then can contain letters, digits or underscores


     Valid identifier:
          value
          number1
          theSumOfTheValues
          the_sum_of_the_values
          val12next16

It better to have a descriptive/meaningful identifier name
that just random characters

          dfgertgdf

     Invalid identifiers:
          12thAddress
          room#17

The variable also needs a type associcated with it
   a type is an encoding scheme

Some Java Types

     int     - an integer value
         ex:  45   0   -17  3

     double  - a floating point value
         ex:  14.9 0.0 3.0 -0.000008

     char    - a character in ASCII format
         ex:  'e'  '%'   '3'

     String  - a collection of characters
         ex:  "Hello"  "true"  "1234"

     boolean - a true or false value
         ex:   true   false


To create a variable: we write the following code

      int  value1;


Syntax:
      <type>  <indentifier> ;



To use a variable, we most often use an assignment statement

Syntax:
      <variable> = <expression> ;

ex: 
       value1 = 10;

       value2 = value1 + 5;

       value1 = value1 + 1;

First:  the expression is evaluated, 
Second: the resulting value is stored in the variable

Primary arthemetic operators
       +    addition
       -    subraction
       *    multiplication
       /    division   

      5 + 4 * 3

      ( )   parentheses

      (5 + 4) * 3

       %    modulus - remainder from an integer division


       9 / 2    ==>   4   integer division

       9.0 / 2.0 ==>  4.5  floating point division