1. Introduction to Computing Dr. Nadeem A Khan

2. Lecture 7

3. Lab on Thursday!

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

5. ► 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.)

6. ► 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.)

7. ► 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

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

9. ► 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.)

10. ► 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= 2.33333 * 2 Picture1.Print count Data Types

11. ► 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

12. ► 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.)

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

14. ► 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.)

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

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

17. ► 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.)

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

19. ► 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.)

20. ► 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.)

21. ► 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.)

22. ► Double Usage:Result 0.3333333(Single precision) 0.333333333333333 (Double precision) => Value of 1/3 represented more accurately by double than by single by double than by single Data Types (Contd.)

23. ► Double Usage:Example Dim sngValue As Single, dblValue As Double Let sngValue= 1/3 Let sngValue= sngValue * 100000 Picture1.Print sngValue Let dblValue= 1/3 Let dblValue= dblValue * 100000 Picture1.Print dblValue Data Types (Contd.)

24. ► Double Usage:Result 33333.34(Single precision; rounding error) 33333.3333333333 (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.)

25. ► Currency Storage: 8 bytes Range: -922,337,203,685,477.5808 to 922,337,203,685,477.5807 922,337,203,685,477.5807Declaration: Dim curRevenue As Currency (declares a Currency type variable curRevenue) Data Types (Contd.)

26. ► 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.)

27. ► Currency Usage:Result 0.3333 33333.3333 =>- The decimal point is NOT floating; - Could be used for currency and scientific research - No rounding problems for high values Data Types (Contd.)

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

29. Local vs Form Variables

30. 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

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

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

33. 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 1.414214  Sqr(30*2+4) is 8

34. 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

35. 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”

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

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

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

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

40. 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

41. Built-in Functions (Contd.) ► FunctionString Value Format$(12345.628, “Standard”)12,345.63 Format$(12345.628, “Currency”)$12,345.63 Format$(-1234, “Standard”)-1,234.00 Format$(-1234, “Standard”)-1,234.00 Format$(-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

42. Built-in Functions (Contd.) ► FunctionString Value Format$(1/4, “Standard”)? Format$(“.2”, “Currency”)? Format$(-1234.8, “Currency”)?

43. Built-in Functions (Contd.) ► FunctionString Value Format$(1/4, “Standard”)0.25 Format$(“.2”, “Currency”)$0.20 Format$(-1234.8, “Currency”)($1,234.80)

44. Built-in Functions (Contd.) Other functions Other functions ► FunctionString Value Format$(12345.628, “#,0”)12,346 Format$(-3.6, “#,0”)-4 Format$(12345.678, “Percent”)1234567.80% Format$(12345.678, “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

45. Built-in Functions (Contd.) ► FunctionString Value Format$(12345.628, “#,0”)12,346 Format$(-3.6, “#,0”)-4 =>Result: Rounded; =>Result: Rounded; Commas every three places to the left of the decimal point

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

47. Built-in Functions (Contd.) ► FunctionString Value Format$(12345.628, “Percent”)1234562.80% =>Result: Multiplied by 100; trailing % sign; two digits after decimal

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

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

50. Built-in Functions (Contd.) ► FunctionString Value Format$(12345.628, “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;

51. Built-in Functions (Contd.) ► FunctionString Value Format$(-600.228, “Scientific”)? Format$(1/8, “Scientific”)?

52. Built-in Functions (Contd.) ► FunctionString Value Format$(-600.228, “Scientific”)-6.00E+02 Format$(1/8, “Scientific”)-1.25E-01

53. 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

54. Built-in Functions (Contd.) Fixed length string formatting: Fixed length string formatting: ► FunctionString Value Format$(1234567890, “@@@@@@@@@@”)? Format$(123, “@@@@@@@@@@”)? Format$(“1234.56”, “@@@@@@@@@@”)? Format$(“$1,234.56”, “@@@@@@@@@@”)? Format$(1/4, “@@@@@@@@@@”)?

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

56. 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

57. 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.)

58. 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.)

59. 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

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

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

62. 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

63. Please read Chapter 4 completely