Chapter 8

 Visual Basic includes several built-in mathematical functions ◦ Abs ◦ Sqr ◦ Sgn ◦ IsNumeric ◦ Round ◦ Format ◦ Pmt ◦ PV ◦ FV

 Returns the absolute value of a number  Form: Abs(number)  Example: Dim intNum As Integer intNum = -5 lblAnswer.Caption = Abs(intNum) ‘ 5 will be displayed

 Returns the square root of a number  You can not take a square root of a negative number  Form: Sqr(number)  Example: Dim intNum As Integer intNum = 9 lblAns.Caption = Sqr(intNum) ‘ 3 will be displayed

 Returns 1,-1,or 0 when the numeric argument is positive, negative or 0 respectively.  Form: Sgn(number)  Example: Dim intNum As Integer intNum = -5 lblAns.Caption = Sgn(intNum) ‘-1 is displayed intNum = 3 lblAns.Caption = Sgn(intNum) ‘1 is displayed

 Returns True if its argument can be evaluated as a number and False if it cannot.  Form: IsNumeric(argument)  Example: Dim strString As String strString = “123” lblAns.Caption = IsNumeric(strString) ‘True strString = “abc” lblAns.Caption = IsNumeric(strString) ‘False lblAns.Caption = IsNumeric(“2+4”) ‘False lblAns.Caption = IsNumeric(2+4) ‘ True

 Rounds numeric data to specified number of decimal places.  Form: Round(number, decimal places)  Example: Dim dblNum As Double dblNum = lblAns.Caption = Round(dblNum, 2) ‘3.46 will be displayed

 Used to format, or change the appearance of, numeric data.  Form: Format(number, “format type”)  Examples: lblAns.Caption = Format(8789, “General Number”) ‘8789 lblAns.Caption = Format(8789, “Currency”) ‘$8, lblAns.Caption = Format(8789, “Fixed”) ‘ lblAns.Caption = Format(8789, “Standard”) ‘8, lblAns.Caption = Format(89, “Percent”) ‘ % lblAns.Caption = Format(1, “Yes/No”) ‘Yes lblAns.Caption = Format(0, “True/False”) ‘False lblAns.Caption = Format(1, “On/Off”) ‘On

 Three business Built-in function Pmt(rate, term, principal) PV(rate, term, payment) FV(rate, term, investment)

Returns the periodic payment for an installment loan. Rate- is the interest rate per period Term – is the total number of payments to be made Principal – is the amount borrowed Example: Calculate the monthly payments on a 30 – year, $100,000 loan with an annual interest rate of 6%. dblPay = Pmt(0.06/12, 360, ) lblAns.Caption = Format(dblPay, “Currency”) ‘$ ***Since payments are monthly, the interest rate must also be computed monthly by dividing the annual rate interest 6% by 12. ***The principal is negative because it is the amount borrowed.

Returns the present value of an investment. Rate- is the interest rate per period Term – is the total number of payments to be made Payment – amount invested per period Example: Determine the cost of financing a car. $250 per month over a 4 year period is applied to a loan with an interest rate of 8%. dblAmount = 250 * 12 * 4 ‘12000 dblPresent = PV(0.08/12, 48, -250) ‘ dblFin = dblAmount – dblPresent lblAns.Caption = Format(dblFin, “Currency”) ‘$1, ***This means that $1, is spent on Financing

Returns what a series of equal payments invested at a fixed interest will be worth after a period of time. Rate- is the interest rate per period Term – is the total number of payments to be made Investment – is the amount invested per period Example: You invest $500 per month in a retirement plan earning 8% interest per year. What would it be worth in 20 years. dblFuture = FV(0.08/12, 240, -500) lblAns.Caption = Format(dblFuture, “ Currency”) ‘$294,510.21

 Allows the user to select a value from a set of values.  Use the Icon to create a List Box Properties of a List Box Name – use the prefix “lst” for the name List – stores a group of strings that makes up the list. Sorted – displays the item in the list in alphabetical order. (Design Time only) Text – stores the selected list item. (Run Time Only) ListCount – can be used at run time to determine number of items in the list.

 Click Event – is executed when the user clicks on an item in the list box.  AddItem Method – is used to add an item to the list ◦ Example: lstControl.AddItem Item ◦ lstControl – is the name of the list and item is a string object or string double quotes added to the list box  Clear – delete List Box contents of the list. ◦ Example: lstControl.Clear

 Also called collapsible list  The icon is used to create it.  Properties: Name – use the prefix “cbo” for the name List – stores a group of strings that makes up the items in the combo box. Sorted – displays the item in the combo box in alphabetical order. (Design Time only) Text – stores the selected item in the combo box. (Run Time Only) ListCount – can be used at run time to determine number of items in the combo box Style – dropdown combo, simple combo, or dropdown list. Runtime use vbComboDropDown, vbComboSimple, or vbComboDrop-DownList.

 Click Event – is executed when the user clicks on an item in the combo box.  AddItem Method – is used to add an item to the list ◦ Example: cboControl.AddItem Item ◦ cboControl – is the name of the list and item is a string object or string double quotes added to the list  Clear – delete Combo Box contents of the list Example: cboControl.Clear