Writeing Procedures and Functions

Posted on 2000-02-29
Medium Priority
Last Modified: 2010-04-16
Can some one please explain in a way that is understandable about how to write functions and procedures?  I need it for a college assignment and our teacher is not very good at his job.  If you can give some examples for me it would be a good help.  Its supposed to be for an electricity company to calculate customers bills.  I don't want it doing for me just enough info so that I can teach myself.  Thanks :0)
Question by:3_Armed_Human
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions

Expert Comment

ID: 2574293
procedures and functions use the same approach and have a little difference (explained later), basically it is a block or part of program which can be 'called' many times from different parts of 'main' program. the structure is:

procedure p1

procedure p2

{main program starts here}
x=0 {some code}
call procedure p1
y=4 {some code}
call procedure p2
x=y+3 {another main part's code}
call procedure p1
etc etc

(this is pseudocode, just for explanation ;-)

ok, here is a 'life example': imagine you have 3 friends and you want to invite them for party, your 'main program' will be
buy food & booze ;-)
invite Peter
invite Adam
invite George
begin party
end party

this means that you have to do the same actions 3 times... which actions ? - inviting ! in this example it would be:
find a phone number of X person
pick up phone
dial that number
ask for X
say 'hi'
tell him about party
return to main program ;-)

you just have replace X with different names 3 times, but actions the same, this why convenient to use procedures. Now a program example, you have to print Y values for 3 different X using formula Y = X * 2 + 1, where Xs are 1,4,6  so the program could be:

Procedure PrintY( X : Byte );
  writeln( X * 2 + 1 );

begin {main}
  PrintY( 1 );
  PrintY( 4 );
  PrintY( 6 );

this is very simple example and not very practical, but you have to understand how execution of program flows, you start in main, PrintY(1) is a call to procedure with 'parameter', so program 'jumps' inside PrintY code, executes using passed parameter, then returns back and continues to PrintY(4).
parameters maybe of any type... you can also pass some values calculated in procedure back to main program, the difference between proc. and funct. is that function always has a result, but proc. - not, so calling is different:
myprocedure(parameters);  {this is call to procedure}
x:=myfunction(parameters); {this is call to function}
honestly in Delphi you can call functions without asigning their result, as procedure, but this is another story....

got it ?

LVL 49

Accepted Solution

dbrunton earned 300 total points
ID: 2575434
Different viewpoint on procedures and functions.

If you were outputting a song that had four verses and a chorus that was repeated between verses and repeated twice at end of song you could create procedures for each verse and for the chorus and assemble as follows.

{* each of these procedures is full of writeln('this is line') or similar *}

procedure verse1;

procedure verse2;

procedure verse3;

procedure verse4;

procedure chorus;


It is possilbe to pass information into the procedures - these are called parameters.

procedure verse5(no : integer);
  if no = 4 then
    writeln('Life is wonderful')
    writeln('Life is hell');

It is possible to get information out of procedures.  Note the var

procedure dble(var no : integer);
  no := no *2;

The above procedure doubles any number passed into it

number := 4;

Functions are designed to return a value.

function triple(no : integer) : integer;
  i : integer;
  i := no * 3:
  tripe := i;

The above function returns the triple of any number passed to it.

number := 4;
newnumber := triple(number);

These are basic procedures and functions.  More complicated variations exist but these are enough for a starter.

How you use and design them depends on what you are required to code.


Expert Comment

ID: 2581648
did you understand or not???

Author Comment

ID: 2582869
Thanks alot, a great help @:0)

Featured Post

On Demand Webinar: Networking for the Cloud Era

Did you know SD-WANs can improve network connectivity? Check out this webinar to learn how an SD-WAN simplified, one-click tool can help you migrate and manage data in the cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Active Directory can easily get cluttered with unused service, user and computer accounts. In this article, I will show you the way I like to implement ADCleanup..
I originally wrote this article to compare SARDU and YUMI, but have now added Easy2Boot, since that is the one I currently use and find the easiest to create and alter.
In this video you will find out how to export Office 365 mailboxes using the built in eDiscovery tool. Bear in mind that although this method might be useful in some cases, using PST files as Office 365 backup is troublesome in a long run (more on t…
Visualize your data even better in Access queries. Given a date and a value, this lesson shows how to compare that value with the previous value, calculate the difference, and display a circle if the value is the same, an up triangle if it increased…
Suggested Courses

765 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question