QBasic- Chapter3

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QBasic- Chapter3 Powered By Docstoc
					QBasic


  Chapter 3 –
  Fundamental
  Statements
QBasic Statement Components

   Keywords
   Constants
    –   Numeric constants
            Real numbers – include decimal points
            Integers – w/out decimal points
            No commas, symbols (only – sign) or blank spaces
            Exponential notation is used
QBasic Statement Components

   Constants
    –   Character string constants
            Alphanumeric data
            Only one set of double quotes
            Length of a string – max 32,767 characters
   Variables
    –   Can only store one value at a time
    –   Referred to by addresses
    –   Variables are named
    –   Only first 40 characters are recognized in QBasic
    –   QBasic does not differentiate between upper & lowercase
    –   Use descriptive variable names
QBasic Statement Components

   Numeric Variables
    –   Supplied by the programmer or
    –   Calculated during program execution
    –   Begins with a letter, followed by letters, digits, and
        periods
    –   Cannot have blank spaces
QBasic Statement Components

   String Variables
    –   Stores character strings
    –   Begins with a letter followed by letters or digits
        and always end with a $
   Keywords
    –   Cannot be used as variable names
    –   READ, LIST, PRINT, LET and END
Simple QBasic Statements

   CLS – Clear Screen
   Documenting a Program
    –   REM
    –   Single quotation mark (‘)
    –   Can be used anywhere in the program

    REM **** This program was created by ***
    ‘ This program was created by
Simple QBasic Statements

   Assigning Values to Variables
    –   Assignment Statement
    –   LET keyword is optional

    LET Rate = .0825
    LET Tuition = 50.00
    Heading$ = “Inventory Report”
    Classification = 4
Simple QBasic Statements

   Arithmetic Operations
    –   Composed of numeric constants, numeric
        variables, and arithmetic operators
    –   +, -, /, *, ^

    LET Tuition = Hours * 50

    Order of Operations - PEMDAS
Simple QBasic Statements

   Displaying Results
    –PRINT
    PRINT Heading$, Tuition         would result in:
    Your tuition amount is 400.00
   Displaying Literals
    – Group of characters containing just about
      anything
    PRINT “JUNK $%^ 4567”          would result in:
    JUNK $%^ 4567
Simple QBasic Statements

   END
    –   Stops program execution


   Immediate Window
    –   Execute statements as soon as ENTER is
        pressed
Simple QBasic Statements

   HELP
    –   F1 key or HELP menu
    –   Highlight menu option & then press F1 or right
        mouse button
    –   Press ESC to close HELP screen
    –   Alt-H for list of HELP topics
   Smart Editor

				
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