Introduction to Computing Dr. Nadeem A Khan

Lecture 4

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 (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,

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

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.)

The ANSI (ASCII) Code ► A 7 bit code representing one of the 95 characters (including space) ► Normally one byte is used to store this code

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.)

Read Chapter 4 completely

Decisions

Decision Structure: Flowchart Process Step (s) 2 Is Condition True Process Step (s) 1

IF BLOCKS IF condition Then action1Else action 2 action 2 End If

IF BLOCK (Contd.) ► Complete the program: Identifies and displays the larger value and its variable (assume unequal values) Sub Command1_Click Dim a As Single, b As Single, largerVal As Single Let a=4 Let b=5... Picture1. Print “Its value is:”;largerVal End Sub

IF BLOCK (Contd.) Sub Command1_Click Dim a As Single, b As Single, largerVal As Single Let a=4 Let b=5 If a>b Then Picture1.Print “a has the larger value” largerVal=aElse Picture1.Print “b has the larger value” largerVal=b End If Picture1. Print “Its value is:”;largerVal End Sub

IF BLOCK (Contd.) Result: b has the larger value Its value is: 5

IF BLOCK (Contd.) What the following program will do?

IF BLOCK (Contd.) Sub Command1_Click Dim a As Single, b As Single, largerVal As Single Let a=4 Let b=4 If (a>b) Or (a=b) Then Picture1.Print “a has the larger value” largerVal=aElse Picture1.Print “b has the larger value” largerVal=b End If Picture1. Print “Its value is:”;largerVal End Sub

IF BLOCK (Contd.) Result: a has the larger value Its value is: 4

IF BLOCK EXTENDED IF condition 1 Then action1 ElseIf condition 2 Then action 2 action 2 ElseIf condition 3 Then action 3 End If

IF BLOCK EXTENDED(Contd.) What the following program will do?

IF BLOCK EXTENDED(Contd.) Sub Command1_Click Dim a As Single, b As Single Let a=4 Let b=5 If (a>b) Then Picture1.Print “a has the larger value” ElseIf (a<b) Then Picture1.Print “b has the larger value” Else Picture1.Print “a and b have same value” End If End Sub

IF BLOCK EXTENDED (Contd.) Result: b has the larger value

Conditions

Conditions: Examples ► ExpressionTrue/False 2 < 5? -5 > -2.5? 1 < 1? 1 = 1? 3.5 <= 3.5? -9 >= -35? -2 <> -3?

Conditions: Examples (Contd.) ► ExpressionTrue/False 2 < 5True -5 > -2.5False 1 < 1False 1 = 1True 3.5 <= 3.5True -9 >= -35True -2 <> -3True

Conditions: Examples (Contd.) ► ExpressionTrue/False “cat” < “dog”? “cart” < “cat”? “cat” < “catalog”? “9W” < “bat”? “Dog” < “cat” ? “Sales-99” <= “Sales-retail”?

Conditions: Examples (Contd.) ► For strings use the ANSI (or ASCI) table CharactersANSI(ASCI) Value CharactersANSI(ASCI) Value Digits (0-9)48-57 Upper Case (A-Z)65-90 Lower Case (a-z) ► Compare two strings character by character

Conditions: Examples (Contd.) ► ExpressionTrue/False “cat” < “dog”True “cart” < “cat”True “cat” < “catalog”True “9W” < “bat”True “Dog” < “cat” True “Sales-99 <= “Sales-retail”True

Conditions: Examples (Contd.) ► Assume a= 4; b= 3; c=“hello”; d=“bye” ► ExpressionTrue/False (a + b) < 2*a? (Len(c) - b) = (a/2)? c < “good” & d?

Conditions: Examples (Contd.) ► Assume a= 4; b= 3; c=“hello”; d=“bye” ► ExpressionTrue/False (a + b) < 2*aTrue (Len(c) - b) = (a/2)True c < “good” & dFalse

Conditions (Contd.) ► Condition is an expression involving relational operators; it is either True or False ► Relational operators: =; <>; ; =

Conditions (Contd.) ► Complex Conditions: Conditions joined by Logical Operators  cond1 And cond2  cond1 Or cond2  Not cond1

Conditions: Examples (Contd.) ► Assume n= 4; answ=“Y” ► ExpressionTrue/False (2<n)And(n<6) ? Not(n<6)? (answ=“Y”) Or (answ=“y”)?

Conditions: Examples (Contd.) ► Assume n= 4; answ=“Y” ► ExpressionTrue/False (2<n)And(n<6) True Not(n<6)False (answ=“Y”) Or (answ=“y”)True

Conditions (Contd.) ► Operator hierarchy: In decreasing order of priority:  Arithemetic  Relational  Logical ► Logical operator hierarchy: In decreasing order of priority:  Not  And  Or

Conditions (Contd.) => - Tie: Left most operator is first - Use parantheses