CS0004: Introduction to Programming

1. CS0004: Introduction to Programming Input and Output

2. Review • A String is… • a sequence of characters that is treated as a single item • A String literal is surround by… • double quotes (“”) • Typecasting is… • converting from one type to another • Explicit Typecasting Functions • CDbl(parameter) – typecasts to double • CInt(parameter) – typecasts to integer • CStr(parameter) – typecasts to string • Concatenation is… • combining multiple strings into one string • The concatenation operator is… • &

3. Review • Two options that should be turned on in every program you write… • Option Strict On • Option Explicit On • Some string methods and properties are… • Length • ToUpper • ToLower • Trim • Substring • IndexOf

4. Formatting Numbers • VB provides functions for formatting numbers to familiar forms. • Note: These all return strings • Specify the number of decimal places FormatNumber(n,r) Example: FormatNumber(1232.2342, 3) returns 1,232.234 • Return in currency form FormatCurrency(n,r) Example: FormatCurrency(1232.2343, 2) returns $1,232.23 • Return in a percent form FormatPercent(n,r) Example: FormatPercent(0.3452, 2) returns 34.53%

5. Masked Text Box • You can avoid doing data validation in some cases by forcing the user to input data in a specific form using a masked text box. • Demo • Create control • Click on the triangle on the control • Select “Set Mask” • Custom Masks • See course webpage

6. Date Data Type • Visual Basic also provides a date data type Dim theDate As Date • Date literals are surrounded by pound signs (#) Dim theDate As Date = #2/7/2011# • You can convert dates into strings of different formats much like the number data types FormatDateTime(theDate, DateFormat.LongDate) • See the course webpage for different date formats • Some date functions • Today • Returns today’s date • DateDiff(DateInterval.Day, date1, date2) • Returns the number of days between date1 and date2 as an integer. • See course webpage for different date intervals • theDate.AddYears(n), theDate.AddMonths(n), and theDate.AddDays(n) • Returns the date after adding n years, months, and days (respectively) to theDate. • CDate(dateString) • Typecasts the string dataString to a date data type

7. Date Example • New Topics: • Date date type • Date literals • Masked text box • CDate typecasting • Today function • FormatDateTime function • DateDiff function • AddDays function

8. Input Dialog Box • Sometimes we want to get a piece of information once and do not want to waste screen space with a text box and a label. For this we use an input dialog box. InputBox(prompt, title) • prompt is the message displayed inside of the dialog box • title is the text displayed in the title of the dialog box • This function returns the string that is in the text box in the dialog box when the user presses OK. • Thus, you want to store the result returned into a variable Dim userInput As String userInput = InputBox(“Please Enter Input”, “Input”)

9. Output Dialog Box • You can also display a dialog box that takes no input, but just displays a message. This is called an output dialog box. MessageBox.Show(prompt, title) • prompt and title are the same as in the input dialog box. • This displays a dialog with the message and an OK button.

10. Dialog Boxes Examples • New Topics • Variable scope • OnLoad event procedure • Input dialog box • Output dialog box

11. Named Constants • Sometimes you want to define a variable that will keep the same value throughout the running of the program. These are called constants. Const CONSTANT_NAME As Type = value • Notes: • Const makes the constant not able to take a different value after initialization • The name of the constant should be all in caps and have underscores instead of camel case for different words • You need to initialize the constant for it to have a value