Introduction to Computing Dr. Nadeem A Khan

Lecture 7

Lab on Thursday!

► Already known:  String  Single  Integer Data Types

► Strings Storage: 10 bytes + string length Range: 0 to app. 2 billions chars. Declaration: Dim strVarLen As String (declares a string of a variable length) (declares a string of a variable length) Data Types (Contd.)

► Fixed-Length Strings Storage: Length of string Range: 1 to app. 65, 400 chars. Declaration: Dim strFixLen As String * 2 (declares a string of a fix size of 2 chars.) Data Types (Contd.)

► Fixed-Length Strings Usage:Example Dim strText As String * 5 Let strText = “Hello” Picture1.Print strText Let strText = “H” Picture1.Print strText Let strText = “HelloWorld” Picture1.Print strText Data Types

► Fixed-Length Strings Usage:Result: Hello(Complete string) H…. (H followed 4 spaces) Hello(First 5 characters only) => The length is fix Data Types

► Integers Storage: 2 bytes Range: -32,768 to 32,767 Declaration: Dim intExample As Integer (declares intExample as an Integer variable) (declares intExample as an Integer variable) Data Types (Contd.)

► Integers Usage:Example Dim count As Integer Let count= 6 Picture1.Print count Let count= count+1 Picture1.Print count Let count= 6/5 Picture1.Print count Let count= * 2 Picture1.Print count Data Types

► Integer Usage:Result67 1 (rounding to lower value) 5(rounding to higher value) => takes only whole number values => takes only whole number values Data Types

► Long (Integer) Storage: 4 bytes Range: -2,147,483,648 to 2,147,483,647 Declaration: Dim lngExample As Long (declares lntExample as a long variable) (declares lntExample as a long variable) Data Types (Contd.)

► Long (Integer) Usage: Same as Integer Type except the range is much larger much larger Data Types (Contd.)

► Byte Storage: 1 byte Range: 0 to 255 Declaration: Dim bytExample As Byte (declares bytExample as a Byte type variable) (declares bytExample as a Byte type variable) Data Types (Contd.)

► Byte Usage: Same as Integer Type except the range is positive and much smaller positive and much smaller Data Types (Contd.)

► Boolean Storage: 2 bytes Range: TRUE(1) or FALSE(0) Declaration: Dim blnState As Boolean (declares a Boolean type variable blnState) Data Types (Contd.)

► Boolean Usage:Example Dim blnExample As Boolean Let blnExample= FALSE Picture1.Print blnExample Let blnExample= 1 Picture1.Print blnExample Let blnExample= 6 Picture1.Print blnExample Let blnExample= -8*7+5.2 Let blnExample= -8*7+5.2 Picture1.Print blnExample Data Types (Contd.)

► Boolean Usage:Example FALSE FALSE TRUE TRUE =>Values other than 0 are TRUE =>Values other than 0 are TRUE Data Types (Contd.)

► Single (Precision Floating-Point) Storage: 4 bytes Range: -3.4…E38 to -1.4…E-45 (negative) 1.4…E-45 to 3.4…E38 (positive) Declaration: Dim sngAverage As Single (declares a Single type variable sngAverage) Data Types (Contd.)

► Double (Precision Floating-Point) Storage: 8 bytes Range: -1.7…E308 to -4.9…E-324 (negative) 4.9…E-324 to 1.7…E308 (positive) 4.9…E-324 to 1.7…E308 (positive)Declaration: Dim dblAverage As Double (declares a Double type variable dblAverage) Data Types (Contd.)

► Double Usage:Example Dim sngValue As Single, dblValue As Double Let sngValue= 1/3 Picture1.Print sngValue Let dblValue= 1/3 Picture1.Print dblValue Data Types (Contd.)

► Double Usage:Result (Single precision) (Double precision) => Value of 1/3 represented more accurately by double than by single by double than by single Data Types (Contd.)

► Double Usage:Example Dim sngValue As Single, dblValue As Double Let sngValue= 1/3 Let sngValue= sngValue * Picture1.Print sngValue Let dblValue= 1/3 Let dblValue= dblValue * Picture1.Print dblValue Data Types (Contd.)

► Double Usage:Result (Single precision; rounding error) (Double precision) => - The decimal point is floating; - Eventually both will be subjected to rounding errors value increases to large values value increases to large values - Still Double will remain more precise than Single Data Types (Contd.)

► Currency Storage: 8 bytes Range: -922,337,203,685, to 922,337,203,685, ,337,203,685, Declaration: Dim curRevenue As Currency (declares a Currency type variable curRevenue) Data Types (Contd.)

► Currency Usage:Example Dim curValue As Currency Let curValue= 1/3 Picture1.Print curValue Let curValue= 100*1/3 Picture1.Print curValue Data Types (Contd.)

► Currency Usage:Result =>- The decimal point is NOT floating; - Could be used for currency and scientific research - No rounding problems for high values Data Types (Contd.)

► Even more data types  Date Variable: for date and time  Object Variable  Variant Variable  ………. Read the book for more info. Data Types (Contd.)

Local vs Form Variables

Not only +,-,*,^ But also: But also: \ opeartor e.g: 5.1\2.04= 2 \ opeartor e.g: 5.1\2.04= 2 MOD operator e.g: 15.2 MOD 6=3 MOD operator e.g: 15.2 MOD 6=3 => First round to closest integers before operation More on Operators

More on Operators (Contd.) ► Operator Precedence 1. ^ 2.- operator (indicating a negative value) 3. * and / operator 4. \ operator 5. MOD operator 6. + and - operator

Built-in Functions ► Take one or more input values ► Return an output value ► Already seen:  Val(..), Str$(..), Asc(..), Chr(..)

Built-in Numeric Functions ► Sqr: calculates square-root and returns the value as double data type e.g: e.g:  Sqr(9) is 3  Sqr(0) is 0  Sqr(2) is  Sqr(30*2+4) is 8

Built-in Numeric Functions ► Int: Greatest integer less than and equal to a number e.g: e.g:  Int(2.7) is 2  Int(3) is 3  Int(-2.7) is -3

Built-in String Functions ► Left$, Mid$, Right$, UCase$, Trim$ Left$(“fanatic”, 3) is “fan”Right$(“fanatic”, 3) is “tic” Left$(“12/15/93”,2) is “12”Right$(“12/15/93”, 2) is “93” Mid$(“fanatic”, 5,1) is “t”Mid$(“12/15/93”,4, 2) is “15” Ucase(“Disk”) is “DISK”Ucase(“12two”) is “12TWO” Trim$(“ 1 2 ”) is “1 2”Trim$(“-12 ”) is “-12”

Built-in Functions (Contd.) ► Len Len(“Shenandoah”) is ? Len(“Just a moment”) is ? Len(“m”) is ?

Built-in Functions (Contd.) ► Len Len(“Shenandoah”) is 10 Len(“Just a moment”) is 13 Len(“m”) is 1

Built-in Functions (Contd.) ► Instr Instr(“Shenandoah”, “nand”) is ? Instr(“Just a moment”, “ ”) is ? Instr(“Croissant”, “ist”) is ?

Built-in Functions (Contd.) ► Instr Instr(“Shenandoah”, “nand”) is 4 Instr(“Just a moment”, “ ”) is 5 Instr(“Croissant”, “ist”) is 0

Built-in Functions (Contd.) ► Format$ Format$(num, fmt) num: number, numeric expression, string of a number fmt: format string Result => String consisting of a formatted version of the number

Built-in Functions (Contd.) ► FunctionString Value Format$( , “Standard”)12, Format$( , “Currency”)$12, Format$(-1234, “Standard”)-1, Format$(-1234, “Standard”)-1, Format$(-1234, “Currency”)($1,234.00) Format$(-1234, “Currency”)($1,234.00) =>Result: two digits after decimal; Commas every three places to the left of the decimal point; leading ‘$’ sign for currency

Built-in Functions (Contd.) ► FunctionString Value Format$(1/4, “Standard”)? Format$(“.2”, “Currency”)? Format$( , “Currency”)?

Built-in Functions (Contd.) ► FunctionString Value Format$(1/4, “Standard”)0.25 Format$(“.2”, “Currency”)$0.20 Format$( , “Currency”)($1,234.80)

Built-in Functions (Contd.) Other functions Other functions ► FunctionString Value Format$( , “#,0”)12,346 Format$(-3.6, “#,0”)-4 Format$( , “Percent”) % Format$( , “Scientific”)1.23E+04 Format$(2/3/03, “Long Date”)Monday February 3, 2003 Format$(2/3/03, “Medium Date”)03-Feb-03 =>More examples on following slides

Built-in Functions (Contd.) ► FunctionString Value Format$( , “#,0”)12,346 Format$(-3.6, “#,0”)-4 =>Result: Rounded; =>Result: Rounded; Commas every three places to the left of the decimal point

Built-in Functions (Contd.) ► FunctionString Value Format$(123.82, “#,0”)? Format$(-3.2, “#,0”)?

Built-in Functions (Contd.) ► FunctionString Value Format$( , “Percent”) % =>Result: Multiplied by 100; trailing % sign; two digits after decimal

Built-in Functions (Contd.) ► FunctionString Value Format$(.06265, “Percent”)? Format$(1/8, “Percent”)?

Built-in Functions (Contd.) ► FunctionString Value Format$(.06265, “Percent”)6.27% Format$(1/8, “Percent”)12.50%

Built-in Functions (Contd.) ► FunctionString Value Format$( , “Scientific”)1.23E+04 =>Result: first number between 1 and 9.99 and of two digits after decimal; and of two digits after decimal; Exponent value preceded by E and sign; Exponent value preceded by E and sign;

Built-in Functions (Contd.) ► FunctionString Value Format$( , “Scientific”)? Format$(1/8, “Scientific”)?

Built-in Functions (Contd.) ► FunctionString Value Format$( , “Scientific”)-6.00E+02 Format$(1/8, “Scientific”)-1.25E-01

Built-in Functions (Contd.) Formatting dates: Formatting dates: ► FunctionString Value Format$(“7/4/96”, “Long Date”)Thursday, July 4, 1996 Format$(“7/4/96”, “Medium Date”) 04-Jul-96

Built-in Functions (Contd.) Fixed length string formatting: Fixed length string formatting: ► FunctionString Value Format$( , Format$(123, Format$(“ ”, Format$(“$1,234.56”, Format$(1/4,

Built-in Functions (Contd.) Abs(10) is 10 Abs(-10) is 10 Sgn(10) is 1 Sgn(0) is 0 Sgn(-10) is -1

Sub Text1_KeyPress(KeyAscii as Integer) statements statements End Sub ► Text1_KeyPress event will occur when Text1 has the focus and a key is pressed Text1 has the focus and a key is pressed The Keypress Event Procedure

Sub Text1_KeyPress(KeyAscii as Integer) statements statements End Sub ► Keyascii  is a variable (of type Integer)  gets the ANSI value of the pressed key  value is used to display the corresponding character in the Text1 at the end of this procedure The Keypress Event Procedure (Contd.)

What will happen in these cases? Sub Text1_KeyPress(KeyAscii as Integer) Let KeyAscii =65 Let KeyAscii =65 End Sub Sub Text1_KeyPress(KeyAscii as Integer) Let KeyAscii =0 Let KeyAscii =0 End Sub The Keypress Event Procedure (Contd.)

Generating Random Numbers The function: Rnd The function: Rnd ► Generates a random number from 0 up to but not including 1 Picture1.Print Rnd‘print a different number each time Let numvar= Rnd‘a random value is assigned

Generating Random Numbers (Contd.) The function: Rnd The function: Rnd Display numbers from the set {1,2,3,4,5,6} randomly!

Generating Random Numbers (Contd.) The statement: Randomize Timer? The statement: Randomize Timer?

Generating Random Numbers (Contd.) The statement: Randomize Timer The statement: Randomize Timer Sub Command1_Click ( ) Rem Display a lottery number Picture1.Cls Randomize Timer Picture1.Print Int(10*Rnd); Picture1.Print Int(10*Rnd) End Sub

Please read Chapter 4 completely