Control Structures in Visual Basic


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Control Structures in Visual Basic

  1. 1. Control Structures In Visual Basic Submitted By: Sakar Chiolunkar Shashank Baghel Tushar jain 12C3045 12C3053 LOGO 12C3062
  2. 2. Control Statement The order in which statements are executed in a program is called the flow of control. In a sense, the computer is under the control of one statement at a time. When a statement has been executed, control is turned over to the next statement (like a baton being passed in a relay race). Flow of control is normally sequential. That is, when one statement is finished executing, control passes to the next statement in the pro- gram. If we want the flow of control to be nonsequential, you can use control structure. Company Logo
  3. 3. Control Flow In a program, statements may be executed sequentially, selectively or iteratively. Every programming language provides constructs to support sequence, selection or iteration. So there are three types of programming constructs :  Sequence  Functions and Procedures  Selection   If...Then...Else statement Select Case statement  Iterative   Company Logo For...Next Loop statement Do...Loop statement
  4. 4. Sequential Construct The sequential construct means the statements are being executed sequentially. This represents the default flow of statements. Statement 1 Statement 2 Statement 3
  5. 5. Selection Construct The selection construct means the execution of statement(s) depending upon the condition-test. If a condition evaluates to true, a course-of-action (a set of statements) is followed otherwise another course-of-action is followed. This construct is also called decision construct as it helps in decision making. Condition ? true Statement 1 false One course-of-action Statement 1 Another course of action Statement 2 Statement 2
  6. 6. If...Then...Else statement Perhaps the most important statement in a program is the If statement and then its statements. In other words If.. Then.. Else statement provides an alternate choice to the user i.e. if the condition is true then a set of statements are executed otherwise another set of statements are executed. In Visual Basic we use three types of ‘IF’ statements: 1. Simple If 2. If Else 3. Nested If
  7. 7. If...Then...Else statement Syntax : true If (boolean Expression) Then VB Statement(s) Else VB Statement(s) End If Statement Condition ? false Statement
  8. 8. Select Case statement If we have a lot of conditional statements, using If..Then..Else could be very messy. For multiple conditional statements, it is better to use Select Case or Select Case allows multi way branching through the code. Syntax : Select Case expression ‘expression maybe string or numeric Case value1 Block of one or more VB statements Case value2 Block of one or more VB Statements Case value3 Block of one or more VB statements Case value4 . . . Case Else Block of one or more VB Statements End Select
  9. 9. Select Case statement Case 1 true Case 1 Statements false Case 2 true Case 2 Statements false Case N true Case Else Statements Case N Statements
  10. 10. Iterative Constructs The iterative or repetitive constructs means repetition of a set-of-statements depending upon a condition-test. A set-of-statements are repeated again and again till the condition or Boolean Expression evaluates to true. The iteration constructs are also called as looping constructs. false The exit condition Condition ? True Statement 1 The loop body Statement 2
  11. 11. For...Next Loop statement Repeats a group of statements a specified number of times. Syntax : For counter [ As datatype ] = start To end [ Step step ] [ statements ] [ Continue For ] [ statements ] [ Exit For ] [ statements ] Next [ counter ]
  12. 12. Do...Loop statement Repeats a block of statements while a Boolean condition is True or until the condition becomes True. Syntax : Do { While | Until } condition [ statements ] [ Continue Do ] [ statements ] [ Exit Do ] [ statements ] Loop -orDo [ statements ] [ Continue Do ] [ statements ] [ Exit Do ] [ statements ] Loop { While | Until } condition
  13. 13. Thank You.....