At the end of this lab you should be able to:
- Design interface on your own.
- Construct logical statements where needed.
- Write conditional if/else statement(s).
- Use the input box function to read input.
- Writing program statements using loops.
- Construct user-defined functions and sub procedures.
o Understand how functions are used in VB.NET programming.
o Learn how to construct procedures that don't return a result
o Learn how to construct Functions that return values.
o Explore variables as parameters/arguments.
Pre-Lab
i. Read the description of each activity carefully and thoroughly so that you understand what the problem is about i.e. what are the requirements and possible solutions for the given problem.
ii. Once you understand each activity requirement(s), then try to do a few examples on paper as to ascertain what your application output may be.
iii. Then design the interface keeping in mind what the user needs to input into the application; tasks that the program needs to perform and what needs to be displayed as output.
Activity 1: Area of a rectangle
Write the statements to create a Function procedure named Area that determines the area of a rectangle (length * width), and then returns this value. The function should accept two arguments having a data type of Double and return a Double.
Activity 2: Clear All
Write the statements to create a Sub procedure named ClearAll. This procedure should accept no arguments. The statements in the procedure should remove the text from the following textboxes:
txtName, txtAddress, txtCity, and txtState. The procedure should only be visible to the form containing the declaration.
Activity 3: Cat
Write the statements to create a Function procedure named Cat, with four String arguments. The function procedure should concatenate the four arguments and return the result.
Activity 4: Sum of Series
Write a Function procedure that calculates the sum of the following mathematical series, and then returns the sum:
1+ 1/2 + 1/3 + 1/4 + 1/5 + ..........+ 1/n
The function should accept one argument having a data type of Integer and return a Double.
Activity 5: Divisible by 5
Write a Function procedure that determines whether a given Integer is divisible by 5 or not. The function should accept one argument having a data type of Integer and return True if that Integer is divisible by 5, False otherwise.
Activity 6: Powers of 2
You need to modify this application, see what to do below.
Computers use the binary number system, which is based on powers of 2. Create a Visual Basic Windows application that displays the positive powers of 2. Have a command button on your interface which when clicked displays an input box that the user will use to enter the exponent (an integer). You program should then calculate and display 2 to that exponent in a label or MsgBox with the appropriate formatting.
The following algorithm may help you.
1. Read exponent from input box.
2. Convert exponent to integer
3. Calculate 2 to the exponent *
4. Display result
In this activity, to calculate 2 to the exponent, do not use the arithmetic operator (^). Instead write a loop to repeat the loop ‘exponent' number of times with each pass multiplying the result by 2. For example, if exponent entered was 3 then the following loop calculates the value of 2 to the power 3.
Dim intCount As Integer = 0
Dim dblResult As Double = 1; ' why is it important to
' initialize this variable to 1?
Do While intCount < intExponent
dblResult = dblResult * 2.0
intCount = intCount + 1
Loop
What to do:
1. Write a Function procedure that implements the above code to calculate 2 to the exponent. This function should accept an Integer value (an exponent) and calculate 2 to that exponent, returning this calculated value in the end.
2. After the function is written, in step 3 of the above algorithm, call this function, passing in the necessary parameter. Store the return value in an appropriate variable; contents of which will be displayed in step 4.