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FUNCTIONS& PROCUDURES:

1. Procedures andfunctions provides a means of producing structured programs.

2. Rather than repeating the same operations at several different places in the program, theycan be placed in a procedure or function.

3. This not only makes the program easier to read, but saves a lot of time and effort in

maintaining the program.PROCEDURES:

1. A procedure is a block of code that performs some operation.

2. A procedure is a block of isual !asic statements inside "ub, #nd "ub statements.3. Procedures do not return values.

basic Syntax for a procedure is:

$Private % Public&$"tatic& "ub proc'ame ($arglist&)

Public

*ndicates that the procedure is available to all modules. *f +ption Private is

used in the module, the procedure is not available to modules outside of

the proect.

Private*ndicates that the procedure is only available to other procedures or

functions in the current module or form.

"tatic*ndicates that all variables declared -ithin the procedure are retained, even

-hen the procedure is out of scope.

proc'ame

The name of the procedure. ust be uni/ue to the module if declared

Private, other-ise uni/ue to the proect. The name of the procedurefollo-s the naming rule for ariables.

arglist

A list of variables passed to the procedure as arguments, and their data

types. ultiple arguments are separated by commas. Arguments may be

+ptional, and may be Read +nly.

Visual Basic supports two ways of passin para!"t"rs to functions# By $alu" an% y

r"f"r"nc"#

byval :'# 0or this, -e have t-o key-ords. !yal and !yRef. hen -e pass arguments by value,

the function -orks only -ith the copies of the values.

(# This may lead to performance overheads, -hen -e -ork -ith large amounts of data.

)# !yal indicates the variable -as passed by value, and any changes made -ithin theprocedure to the variable -ill not be reflected to -here the procedure -as called as its

only a copy.

S*+P,E PRO-R*+ FOR B.V*, :

Private 0unction Add(!yal As *nteger, !yal y As *nteger) As *nteger

Add 4 5 y#nd 0unction

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Private "ub 0orm67oad()

8im a As *nteger 8im b As *nteger

8im c As *nteger

a 4 32

b 4 9:

c 4 Add(a, b)

sg!o c

#nd "ubby ref :

1. hen -e pass values by reference, the function receives a reference to the actual values.2. The original values are affected, -hen modified. This -ay of passing values is more time

and space efficient. +n the other hand, it is more error prone.

3. !yRef indicates the variable is passed by reference, and any changes made -ithin theprocedure to the variable -ill be reflected to -here the procedure -as called.

:. !yRef is the default in isual !asic 9

S*+P,E PRO-R*+ FOR B.REF :

Pri$at" Su Swap/ByR"f 0 *s Int""r1 ByR"f y *s Int""r2

8im temp As *nteger

temp 4

4 y y 4 temp

#nd "ub

Pri$at" Su DisplayVals/ByR"f a *s Int""r1 ByVal *s Int""r2

sg!o ;a 4 ; < ="tr(a) < vb=r7f < ;b 4 ; < ="tr(b)

#nd "ub

Pri$at" Su For!3,oa%/2

8im a As *nteger

8im b As *nteger

a 4 1>

b 4 12

8isplay values, s-ap, and display again

8isplayals a, b

Call Swap(a, b)

DisplayVals a, b

En% Su

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