Subs and Functions

1
Subs and Functions

• Using Subs or functions to divide problems into
  smaller task.
• E.g. Studying High-dip can be divided into 3
  tasks -
• STUDY_YEAR1( )
• STUDY_YEAR2( )
• STUDY_YEAR3( )

2
Subs

• Subs usually performs repeating task.
• Sample sub
• Sub ComputeTotal ()
• xyz
• kkk .
• total total kkk
• End Sub

3
Calling the sub( )

• To call the sub ComputeTotal,
• Just type ComputeTotal ( )
• Or Call ComputeTotal ( )
• Example
• quantity textbox1.text
• Call ComputeTotal ( )
• label1.text total

Sub ComputeTotal() X y Total x
y End sub
4
Passing value to subs

• You can send values to a Sub, e.g.
  ComputeTotal (5, 6)
• X gets the value 5 and Y gets 6
• total becomes 30.

Sub ComputeTotal( x as integer, y as
integer) Total x y End sub
5
Passing byVal or byRef

• byVal the sub gets the value.
• byRef the parameter points to and uses the
  variables.
• E.g. ComputeTotal(quant, price)
• When passing by reference, changing x is the same
  as changing quant. Therefore, quant 0
• and price 0 after the sub.

Sub ComputeTotal( byRef x as integer, byRef y
as integer) Total x y x 0 y 0 End sub
6
Functions

• Same as sub, but it returns a value.
• Example
• Dim total as integer
• total ComputeTotal(5,6)
• 30 is returned to total. Note the return value is
  of type integer

Sub ComputeTotal( x as integer, y as integer)
as integer Return x y End sub
7
Build in Functions

8
Date Formats

• When your application runs on different machine
  which has different date-time format, you need to
  do format conversion.
• E.g. you save a date to a file
• 29/11/2003 and your computer has a date format
  MM/dd/yyyy.
• And you need to compare the 29/11/2003 with
  today (11/20/2003).

9
Date format conversion

• To convert the BookDate 29/11/2003
• to the format MM/dd/yyyy, use
• BookDate.ToString(MM/dd/yyyy).
• Or convert Today to the format dd/MM/yyyy as
  follows
• todaystring Today.Date.ToString(dd/MM/yyyy)