Subroutines

1
Subroutines Functions

• ITE 285

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Why Use Procedures

• Re-usable code
• Handles the LOGIC of our program
• Logical Modulate Design of Solution
• Easy for programmer to understand later
• Easier to test debug
• Each procedure should accomplish one
  task/sub-task
• Break down each task into sub-tasks

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Types of Procedures

• _______________
• Executes automatically when an event is fired
• Written in form file in specific controls section
  of code window
• _______________
• _______________

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Types of Procedures

• Event Procedure
• Executes automatically when an event is fired
• Written in form file in specific controls section
  of code window
• _______________
• _______________

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Types of Procedures

• Event Procedure
• Executes automatically when an event is fired
• Written in form file in specific controls section
  of code window
• User-Defined Procedures
• _______________

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Types of Procedures

• Event Procedure
• Executes automatically when an event is fired
• Written in form file in specific controls section
  of code window
• User-Defined Procedures
• External Procedures

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User-Defined Procedures

• Must be called by other code
• Keyword __________
• Declared in ___________________ section of form
  file or in a Code Module
• 2 Types
• __________________
• Does not return a value
• Can be an event procedure
• __________________
• Does return a value
• Cannot be an event procedure

8
User-Defined Procedures

• Must be called by other code
• Keyword CALL
• Declared in ___________________ section of form
  file or in a Code Module
• 2 Types
• __________________
• Does not return a value
• Can be an event procedure
• __________________
• Does return a value
• Cannot be an event procedure

9
User-Defined Procedures

• Must be called by other code
• Keyword CALL
• Declared in General Declarations section of form
  file or in a Code Module
• 2 Types
• __________________
• Does not return a value
• Can be an event procedure
• __________________
• Does return a value
• Cannot be an event procedure

10
User-Defined Procedures

• Must be called by other code
• Keyword CALL
• Declared in General Declarations section of form
  file or in a Code Module
• 2 Types
• Sub-Routine
• Does not return a value
• Can be an event procedure
• __________________
• Does return a value
• Cannot be an event procedure

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User-Defined Procedures

• Must be called by other code
• Keyword CALL
• Declared in General Declarations section of form
  file or in a Code Module
• 2 Types
• Sub-Routine
• Does not return a value
• Can be an event procedure
• Function
• Does return a value
• Cannot be an event procedure

12
External Procedures

• Declared in separately compiled modules (code
  libraries)
• Can be called by your code
• Keyword CALL
• CANNOT be used in this class

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User Defined Sub-Routines

• Declared by creating a method ___________ and
  end.
• AccessControlKeyword Sub Name (ParameterName as
  DataType)
• Subroutine Code
• End Sub

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User Defined Sub-Routines

• Declared by creating a method Header and end.
• AccessControlKeyword Sub Name (ParameterName as
  DataType)
• Subroutine Code
• End Sub

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User Defined Sub-Routines

• Example
• Public Sub myFirstSub (ByVal intMyNum as Integer)
• txtGrade.text (intMyNumber 20)
• EndSub

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User Defined Sub-Routines

• Must be called from another line of code
• _______________ of sub-routine is generally
  accepted as the sub-routine call
• Exception External Sub-routines (must use CALL)
• Sample Code

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User Defined Sub-Routines

• Must be called from another line of code
• Name of sub-routine is generally accepted as the
  sub-routine call
• Exception External Sub-routines (must use CALL)
• Sample Code

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Code Module

• To add a Code Module
• Project Menu
• Add Module
• Module Option
• Give it a meaningful name
• Remember Variables and/or Procedures declared
  as DIM are form level will not be accessible
  within a code module (and vise-versa) would
  need to be Public

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Functions

• Will return a value to the calling code
• Must have an associated ________________
• Declared at the end of the function header
• Return a value
• Assign a value to _______________
• Using a _______________ statement with the value
  to return
• A function call is only __________ of a code
  statement
• Must be part of an expression (to handle
  returning value)
• Usually on the right hand side of an assignment
  statement

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Functions

• Will return a value to the calling code
• Must have an associated Data Type
• Declared at the end of the function header
• Return a value
• Assign a value to _______________
• Using a _______________ statement with the value
  to return
• A function call is only __________ of a code
  statement
• Must be part of an expression (to handle
  returning value)
• Usually on the right hand side of an assignment
  statement

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Functions

• Will return a value to the calling code
• Must have an associated Data Type
• Declared at the end of the function header
• Return a value
• Assign a value to Function Name
• Using a _______________ statement with the value
  to return
• A function call is only __________ of a code
  statement
• Must be part of an expression (to handle
  returning value)
• Usually on the right hand side of an assignment
  statement

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Functions

• Will return a value to the calling code
• Must have an associated Data Type
• Declared at the end of the function header
• Return a value
• Assign a value to Function Name
• Using a Return statement with the value to return
• A function call is only __________ of a code
  statement
• Must be part of an expression (to handle
  returning value)
• Usually on the right hand side of an assignment
  statement

23
Functions

• Will return a value to the calling code
• Must have an associated Data Type
• Declared at the end of the function header
• Return a value
• Assign a value to Function Name
• Using a Return statement with the value to return
• A function call is only part of a code statement
• Must be part of an expression (to handle
  returning value)
• Usually on the right hand side of an assignment
  statement

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Functions

• Syntax
• AccessControlKeyword Function Name (ParameterName
  as DataType) as ReturnType
• Function Code
• Set Value to Return
• End Function

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Functions

• Example
• Private Function getName ( ) as String
• Dim strInputName as String
• strInputName InputBox (Enter First Name )
• getName strInputName or Return
  strInputName
• End Function
• Sample Code

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Parameter Passing

• Parameters can be sent to subroutines and/or
  functions
• ________________ list is defined in parenthesis
  within the procedure heading
• ________________ list is designated in the
  procedure call
• These must match in
• _______________
• _______________
• _______________

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Parameter Passing

• Parameters can be sent to subroutines and/or
  functions
• Formal Parameter list is defined in parenthesis
  within the procedure heading
• ________________ list is designated in the
  procedure call
• These must match in
• _______________
• _______________
• _______________

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Parameter Passing

• Parameters can be sent to subroutines and/or
  functions
• Formal Parameter list is defined in parenthesis
  within the procedure heading
• Actual Parameter list is designated in the
  procedure call
• These must match in
• _______________
• _______________
• _______________

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Parameter Passing

• Parameters can be sent to subroutines and/or
  functions
• Formal Parameter list is defined in parenthesis
  within the procedure heading
• Actual Parameter list is designated in the
  procedure call
• These must match in
• Number
• Data Type
• Order

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Parameter Passing

• Defining a Parameter (in the procedure heading)
• Pass by Reference or Pass by Value (more shortly)
• Default is by Value
• Identifier Name
• Associated data type
• Public Sub myFirstSub (ByVal intMyNum as Integer)
• txtGrade.text (intMyNumber 20)
• EndSub

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Parameter Passing

• When _______________ this procedure
• You must send data (values or variables) to match
  formal parameter list
• myFirstSub (25)
• Actual parameter list and formal parameter list
  must match exactly
• Visual Basic does allow for Procedure
  _______________
• Multiple versions of a procedure with different
  parameter lists

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Parameter Passing

• When calling this procedure
• You must send data (values or variables) to match
  formal parameter list
• myFirstSub (25)
• Actual parameter list and formal parameter list
  must match exactly
• Visual Basic does allow for Procedure
  _______________
• Multiple versions of a procedure with different
  parameter lists

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Parameter Passing

• When calling this procedure
• You must send data (values or variables) to match
  formal parameter list
• myFirstSub (25)
• Actual parameter list and formal parameter list
  must match exactly
• Visual Basic does allow for Procedure Overloading
• Multiple versions of a procedure with different
  parameter lists

34
Pass by Value

• Declared with ByVal keyword
• Procedure receives a __________ of the value that
  was sent to the procedure
• A local _______________ will be declared and
  initialized with that value
• Changes made to the value will effect only the
  __________ copy of the variable
• Changes WILL NOT carry back to the calling code

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Pass by Value

• Declared with ByVal keyword
• Procedure receives a copy of the value that was
  sent to the procedure
• A local _______________ will be declared and
  initialized with that value
• Changes made to the value will effect only the
  __________ copy of the variable
• Changes WILL NOT carry back to the calling code

36
Pass by Value

• Declared with ByVal keyword
• Procedure receives a copy of the value that was
  sent to the procedure
• A local variable will be declared and initialized
  with that value
• Changes made to the value will effect only the
  __________ copy of the variable
• Changes WILL NOT carry back to the calling code

37
Pass by Value

• Declared with ByVal keyword
• Procedure receives a copy of the value that was
  sent to the procedure
• A local variable will be declared and initialized
  with that value
• Changes made to the value will effect only the
  local copy of the variable
• Changes WILL NOT carry back to the calling code

38
Pass by Reference

• Declared with ByRef keyword
• Procedures receive the _______________ of the
  variable sent as a parameter
• Local variable is created with the same memory
  location of the original parameter
• Changes made to the value of the local variable
  ______ effect the value of the original
  parameter
• Changes are carried back to the calling code.

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Pass by Reference

• Declared with ByRef keyword
• Procedures receive the memory address of the
  variable sent as a parameter
• Local variable is created with the same memory
  location of the original parameter
• Changes made to the value of the local variable
  ______ effect the value of the original
  parameter
• Changes are carried back to the calling code.

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Pass by Reference

• Declared with ByRef keyword
• Procedures receive the memory address of the
  variable sent as a parameter
• Local variable is created with the same memory
  location of the original parameter
• Changes made to the value of the local variable
  WILL effect the value of the original parameter
• Changes are carried back to the calling code.