Visual BASIC

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Visual BASIC

• Fundamentals

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Algorithms

• An algorithm is a method for solving a problem
• A sequence of precise instructions that leads to
  a solution
• It is a model of the solution
• It should be
• unambiguous
• executable
• terminating

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Problem Solving

• Know
• Need
• Do

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Know

• What do I know?
• What facts am I starting with?
• Define the problem

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Need

• What do I need?
• Whats missing?
• What other facts do I need to find or determine?

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Do

• What do I need to do?
• Develop a method, a solution, an algorithm for
  solving the problem
• Execute the algorithm

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In the Beginning ...

• The first devices to be used were vacumn tubes
• They had two states
• They were hot and required lots of air
  conditioning
• They were fairly big and needed lots of wiring
• They burnt out often

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Getting Smaller ...

• Next came transisters
• They had two states
• They produced far less heat
• They were smaller and therefore needed less
  wiring
• Less wiring meant shorter distances for electrons
  to travel and thus faster computers

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Smaller Yet ...

• Today, we use integrated circuits, which combine
  transisters and other components into
  photographically microtized circuits
• They are essentially cool
• They need very little wiring and therefore are
  even faster

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Try this!

• Problem
• If you had a panel with three light switches, how
  many unique combinations of up and down could you
  create?
• Break into groups of 4
• Work on the problem for 10 minutes
• Go!

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Try this!

• Answer
• Each switch has two possible states(up or down
  )
• 2 ? 2 ? 2 8 possible combinations
• How many combinations for 4 switches?
• 6 switches?
• 8 switches?

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Binary Numbers

• Use two digits, 0 and 1
• Decimal numbers use digits 0 through 9
• The decimal number 23 would be the binary number
  10111
• Bit a binary digit
• Byte an eight digit binary number
• Each bit requires a device with two possible
  states

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Try this!

• What decimal number is each of the following
  binary numbers equal to?
• 1010
• 1001
• 1100
• 111010
• 11111111

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A Basic Computer
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A Basic Computer
CPU
Central Processing Unit - where data is processed
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A Basic Computer
CPU
ROM
Read Only Memory - Manufacturer supplied data and
instructions
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A Basic Computer
CPU
ROM
RAM
Random Access Memory - User supplied data and
instructions
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A Basic Computer
CPU
InputDevice
ROM
RAM
Allows user to supply data to CPU directly
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A Basic Computer
CPU
InputDevice
OutputDevice
ROM
RAM
Allows CPU to send data to user directly
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A Basic Computer
CPU
InputDevice
OutputDevice
ROM
RAM
SecondaryStorage
Semi-permanent storage - device and medium
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Bits Bytes

• Computer instructions are stored using numerical
  codes
• Each family of CPUs has its own instruction set
• An instruction set is a collection of instruction
  codes
• This is why an Intel CPU based program wont
  necessarily run on a Power PC CPU

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Programming Languages

• Machine language
• Assembly language
• Higher level languages
• Interpreted languagesBASIC, APL
• Compiled languagesC, Pascal, Fortran, Cobol

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Machine Language

• The language of the computer (CPU)
• Essentially, the instruction set

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Assembly Language

• Very similar to machine language
• Instruction codes are replaced with short
  abbreviations
• Requires an assembler (program) to translate into
  machine language

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Higher Level Interpreted

• Instructions similar to written sentences and/or
  arithmetic expressions
• Requires an interpreter (program) to translate
  into machine language
• Each instruction is executed immediately after it
  is translated

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Higher Level Compiled

• Instructions similar to written sentences and/or
  arithmetic expressions
• Requires a compiler (program) to translate into
  machine language
• Instructions are first translated, and then the
  entire translated program is executed

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Programming Paradigms

• Procedural
• Functional
• Declarative
• Object-oriented

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Procedural Programming

• Methods (algorithms) are developed to solve
  problem
• Step-by-step solutions
• BASIC, FORTRAN, COBOL, Pascal, C

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Functional Programming

• Discrete components called functions that map
  arguments to outputs
• APL, C, Lisp

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Declarative Programming

• Facts and rules
• PROLOG

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Object-Oriented Programming

• Data structures, instead of instructions, are
  defined as classes of objects
• Each class has its own description
• This includes attributes (data members) and
  methods (member functions)
• C, Eifel, Ada, Visual Basic

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Object-Oriented Programming

• Objects
• a thing, or noun
• described by what they look like and what they do
• Properties
• attributes, or adjectives
• what an object looks like
• For example, color, size, length, etc.
• Methods
• actions, or verbs
• what objects can do

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What is Visual Basic

• A programming language
• Object-oriented
• Event-driven

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Event-Driven Programming

• User actions produces messages
• Messages are passed to objects
• Objects respond via methods

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Assignment

• When a variable is declared, space is allocated
  in the computers memory for the variable
• Each data type requires a different number of
  bytes in memory
• Integer - 2Single - 4Double - 8Boolean -
  1String - 1 per character

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Assignment

• When a variable is assigned a value, the value is
  placed into the variables memory location

Total 2 3 5
Total
10
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Arithmetic Operations

• Addition 2 3
• Subtraction 5 - 2
• Multiplication 10 4
• Division 12 / 3
• Exponentiation 32

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Order of Operations

• Arithmetic expressions are evaluated according to
  the following order of operations
• At each level, operations are evaluated left to
  right
• (1) Parenthesis, Functions, Exponentiation(2)
  Multiplication, Division(3) Addition, Subtraction

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Parenthesis

• Parenthesis are used to alter the order with
  which operations are evaluated
• Ex.
• 4 5 2 equals 14
• (4 5) 2 equals 18

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VB Projects

• Project File
• filename.VBP
• description of the project
• Forms (form modules)
• filename.FRM
• description of objects, and their properties and
  methods
• Standard Code Modules
• filename.BAS
• additional BASIC statements

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VB Objects

• Label
• Static text
• lbl
• Text box
• Dynamic text
• txt
• Command button
• Initiates user-selected action
• cmd

• List box
• Text list
• lst
• Menus
• Nuf said!
• men
• Radio button, Check box
• Selection
• and more ...

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Adding an Object

• Click on icon in object menu
• Position crosshairs for first corner
• Hold down left mouse button

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Adding an Object

• Click on icon in object menu
• Position crosshairs for first corner
• Hold down left mouse button

• Drag crosshairs to opposite object corner
• Release button
• Edit object properties

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Adding a Method

• Double-click on object in frame
• Editing window will appear
• Each method is a subroutine
• Whats a subroutine?
• Well deal with that later
• Add instructions to method
• Execute program to test

Label
Caption
Command
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Try This!

• Develop a method for determining the net pay for
  an employee based upon the employees gross pay,
  federal income tax rate and union dues
• Your method should include names (identifiers)
  for all known and unknown values

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Know?

• Gross pay
• Tax rate
• Union dues

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Need?

• Tax
• Net Pay
• How to calculate the above

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Do?

• Create an algorithm
• Tax is tax rate times gross payTax Tax Rate ?
  Gross Pay
• Net pay is gross pay less all deductionsNet Pay
  Gross Pay - (Tax Union Dues)
• Implement algorithm as program
• Execute program
• (Debug, debug, debug!!!)

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Implement as Program

• Design an interface
• txtGrossPay
• txtTaxRate
• txtUnionDues
• lblTax
• lblNetPay
• cmdCalc
• cmdClear
• cmdExit

Gross Pay
Tax Rate
Union Dues
Tax
Net Pay
Clear
Calculate
Exit
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Implement as Program

• Convert algorithm into program statements

• Dim dTaxRate As Double
• Dim dGrossPay As Double
• Dim dUnionDues As Double
• Dim dNetPay As Double
• cTax dTaxRate dGrossPay
• dNetPay dGrossPay - (dTax dUnionDues)

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Implement as Program

• Implement design in VB
• Add methods for cmdCalc, cmdClear and cmdExit
• Note cmdCalcs method essentially implements the
  algorithm you have devised

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Implement as Program

• Okay
• Go to it!