Chapter 2 Adding comments to your code

As a computer programmer, it is very important to keep a record of what you have done, and other information that relates tou your program. When this information is keept with the code, it is called internal documentation.

There major variations in the Visual Basic code to the example in Chapter 1 is the internal documentation or comments. A single quote (') is used to make a comment about a part of the program. These are used to explain parts of the program coding or to put information into the code for yourself or others to read. Comments are ignored by the computer during processing and are used to help to make the code more readable.

Tips for writing good code for programs

Two programs may appear to do the same thing but one might be much better written than the other. The following is a guidelines to creating the code for programs.

Constant and Variable names should identify the data they represent. An example is PriceOfMilk to reprent the price of a carton of milk. Use Upper and Lower case letters to make it more readable but do not put in spaces..
The screen messages should be easy to read and understand. The user should be told what data to enter and the place where it is to be entered. The purpose of the program should always be stated.
The results should always be clear and correct..
You must test the programs carefully to make sure that they solve the problem and give the correct answers!
The screen design is very important. A good program has an attractive, well thought form which has labels that make its purpose and solutions clear to the user.

Planning

Using a simple sequence of steps, it is possible to construct a range of very useful programs. The planning stage is considered to be very important when creating a computer program because it is here that the programmer decides the steps that the computer must follow to solve the problem.

Problem 2

Ace Auto's pays its sales team a weekly retainer of $600 plus 2% commission on all sales made. You have been commisiioned to write a Visual Basic program that will allow the finance department to calculate the weekly salary for each salesperson.

A Visual Basic Solution is shown below.

Planning

Output

The computer must show the salary of the salesman

Input

The computer must have the value of the sales to do the calculations. The name of the salesperson must also be given although there is no calculations on this..

Processing

The calculation of the salary involves finding 2% of the sales and adding $600.

Forms and Controls

This application only needs one form. By setting the properties of the form and each control, the screen above can be duplicated.

Forms

	Property	Setting
Form	BackColor	(Blue)
	Caption	Ace Autos
	Name	Form1

Controls

This applications needs six Labels, one Image, two TextBoxes and two CommandButtons. The properties and settings for one of each control is shown below.

Object	Property	Setting
Image	Name	ImgLogo
	Picture	Bitmap

Label	Name	LblHeading
	BackStyle	0-Transparent
	Caption	Ace Autos
	Font	Ariel Black
	ForeColor	(Red)

TextBox	Name	TxtSales
	Text	(empty)
	Font	Ariel Black

CommandButton	Name	CmdCalculate
	Caption	&Calculate

Label	Name	LblOut
	Caption	(empty)
	Font	Ariel Black

Coding

Pseudocode .

Get employees name
Get value of the sales
Set Salary To Sales x Commisssion/100 + Retainer
Write Employee name and Salary

Code

A Visual Basic program which could be created using this plan is as follows:

Private Sub CmdCalculate_Click()
  'Author Mike Leishman
  'Date 03/12/97
  'Purpose Calculate the Salary of an employee working for commission

  Const Commission = 2
  Const Retainer = 600

  Dim Employee As String
  Dim Sales As Long
  Dim Salary As Long

  'Data Input
  Employee = TxtName.Text
  Sales = TxtSales.Text

  'Salary Calculation
  Salary = Retainer + Sales * Commission

  'Information Output
  LblOut.Text = "$" & Salary

End Sub

Problems

Padbury Milk delivers milk, cream and juice everyday to the people in Padbury. A weekly account is made and delivered on each Friday. The prices are per carton: milk $2, cream $4 and Juice $3. Write a Visual Basic program to accept the name of the customer and the number of cartons of each product per week. It must then calculate the total amount owing.
Paint'a'Drive is a paint that can be applied to driveways to renew the surface. Jone's Painting Services will paint a driveway for $15 a square meter and a set fee of $75. Mr Jones wants to have a computer program to calculate of the amount of Paint'a'Drive needed. Make a program that will accept the length and width of a driveway. It must then calculate the area of the drive and determine the cost of painting the surface.
Fred's Fencing erects multi-strand wire fences around small fields. Fred knows the lenght and width of the field (in meters) and the number of strands needed. Write a program for Fred so as he will know how much wire he needs to buy to put up a fence.

Author: Mike Leishman

Last Modified June 8 1998