1. Chapter 5 The Do…Loop Statement
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Chapter 5 The Do…Loop Statement
Loop structure that executes a set of statements as long as a condition is true.
The condition is a Boolean expression.
Executes at least once.
The loop below iterates while sum is less than 10: sum = 0; Do sum += 2 Loop While sum < 10
Refer to page 129 in the text.
© 2010 Lawrenceville Press

2. Chapter 5 Alternative Do…Loop
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Chapter 5 Alternative Do…Loop
Executes only if the condition is initially true. May not iterate at all.
The statement sum = 20 Do While sum < 10 sum += 2 Loop does not iterate at all because sum is initially greater than 10.
Refer to page 129 in the text.
© 2010 Lawrenceville Press

3. Chapter 5 Infinite Loops
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Chapter 5 Infinite Loops
A loop that continues executing forever
Can be caused by syntax or logic errors. For example: num = -1 Do num -= 1 'num is decreased by 1 While num < 0
Some errors result in an overflow causing a run-time error.
Refer to page 130 in the text.
An infinite loop can cause an application to stop responding or just "hang". Closing the application window will end the application so that the source of the infinite loop can be located and corrected.
Errors that result in an overflow may generate unexpected results rather than "hanging" the application.
© 2010 Lawrenceville Press

4. Chapter 5 The InputBox Function
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Chapter 5 The InputBox Function
Displays a predefined dialog box that has a prompt, a text box, and OK and Cancel buttons, and then returns a string.
Used to obtain information from the user.
The function is used as part of an assignment statement: stringVar = InputBox(prompt, title)
Clicking Cancel or leaving the text box blank returns Nothing.
The Val() function can be used to convert string data to numeric data.
Refer to pages 132 and 133 in the text.
© 2010 Lawrenceville Press

5. Chapter 5 Accumulator Variables
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Chapter 5 Accumulator Variables
A variable that is incremented by a varying amount.
Often used for keeping a running total.
Should be initialized when declared.
Refer to page 133 in the text.
© 2010 Lawrenceville Press

6. Chapter 5 Assignment Operators
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Chapter 5 Assignment Operators
Operator Operation
*= multiplication and then assignment
/= division and then assignment
\= integer division and then assignment
^= exponentiation and then assignment
Refer to page 133 in the text.
© 2010 Lawrenceville Press

7. A flag, or sentinel, indicates when a loop should stop iterating.
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Chapter 5 Using Flags
A flag, or sentinel, indicates when a loop should stop iterating.
Often a constant.
Code is easier to modify when sentinels are constants declared at the beginning of a procedure.
Refer to page 134 in the text.
© 2010 Lawrenceville Press

8. Chapter 5 The For…Next Statement
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Chapter 5 The For…Next Statement
Loop structure that executes a set of statements a fixed number of times.
Uses a counter to control loop iterations.
The keyword Step can optionally be used to change the amount the counter is incremented or decremented.
The loop below executes until num is equal to 10: For num As Integer = 0 To 10 i += num Next num
Refer to pages 136 and 137 in the text.
© 2010 Lawrenceville Press

9. Chapter 5 The String Class
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Chapter 5 The String Class
Includes properties and methods.
A String object is comprised of a sequence of characters with the first character at index position 0.
String properties include: Chars(index) Length()
Refer to page 138 in the text.
The String data type is a class, which includes properties and methods.
When a class is used to declare a variable, the variable is called an object.
The Chars property returns the character at the specified index position.
The Length property returns the number of characters in the String object.
© 2010 Lawrenceville Press

10. Chapter 5 String Methods
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Chapter 5 String Methods
String methods for manipulating a string include: ToUpper converts a string to all uppercase ToLower converts a string to all lowercase Trim removes spaces from the beginning and end of a string TrimEnd removes spaces from the end of a string TrimStart removes spaces from the beginning of a string PadLeft(len, char) adds a specified character to the beginning of a string until the string is len characters long PadRight(len, char) adds a specified character to the end of a string until the string is len characters long
Refer to page 139 in the text.
© 2010 Lawrenceville Press

11. Chapter 5 String Methods (cont.)
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Chapter 5 String Methods (cont.)
String methods for manipulating a substring: Substring(startPos, numOfChars) returns the substring that is numOfChars in length and starts at startPos Remove(startPos, numOfChars) deletes the substring that is numOfChars in length and starts at startPos Replace(oldString, newString) exchanges every occurrence of oldString with newString Insert(startPos, substring) inserts substring at startPos IndexOf(substring) returns the first position of substring
Refer to pages 139 and 140 in the text.
© 2010 Lawrenceville Press

12. Chapter 5 String Concatenation
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Chapter 5 String Concatenation
Concatenation is joining two or more strings together.
The String method Concat() joins two or more strings. It is a shared method and must be used with the String class, not an object of the class: s = String.Concat("this","and","that")
The &= operator concatenates a string to an existing string: s = "thisand" s &= "that"
The & operator concatenates strings: s = "this" & "and" & "that"
Refer to page 141 in the text.
© 2010 Lawrenceville Press

13. Chapter 5 Space(), vbTab, vbCrLf
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Chapter 5 Space(), vbTab, vbCrLf
The Space() function returns a string of spaces.
vbTab is a built-in constant that represents 8 spaces.
vbCrLf is a built-in constant that represents a carriage return-linefeed combination.
Refer to page 142 in the text.
© 2010 Lawrenceville Press

14. Chapter 5 The Char Structure
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Chapter 5 The Char Structure
A simple form of a class.
Char has two shared methods: ToUpper() ToLower()
The methods must be used with the Char structure: newLetter = Char.ToUpper(letter1)
Refer to page 142 in the text.
© 2010 Lawrenceville Press

15. 11/18/2018 5:46 AM
Chapter 5 Unicode
A digital code with representations for every character in every language and symbol.
Two built-in functions for converting between characters and Unicode: AscW(char) ChrW(integer)
Refer to page 143 in the text.
© 2010 Lawrenceville Press

16. Chapter 5 Comparing Strings
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Chapter 5 Comparing Strings
When relational operators (=, >, <, >=, <=, <>) are used to compare strings, their Unicode values determine the relationship between the strings.
The Compare() method is a better choice to alphabetically compare strings: Compare(string1, string2, case-insensitive) returns 0 if string1 and string2 are the same. A positive number is returned if string1 is greater than string2 and a negative number if string1 is less than string2. case-insensitive should be true if the case of the strings should not be considered.
Refer to page 144 in the text.
© 2010 Lawrenceville Press

17. Chapter 5 The Like Operator
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Chapter 5 The Like Operator
Used to perform a textual comparison between two strings.
Can be used to perform pattern matching. The pattern can include: ? used in place of any single character * used in place of many characters # used in place of any single number [] used to enclose a list of characters - used to indicate a range of characters in a list , used to separate characters in a list
Refer to page 145 in the text.
© 2010 Lawrenceville Press