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An introduction and example of parameter passing by reference as used within the C++ programming language.

Overview

When we pass parameters to functions we usually pass by value; that is the calling function provides several values to the called function as needed. The called function takes these values which have local scope and stores them on the stack using them as needed for whatever processing the functions accomplishes. This is the preferred method when calling user defined specific task functions. The called function passes back a single value as the return item if needed. This has the advantage of a closed communications model with everything being neatly passed in as values and any needed item returned back as a parameter.

By necessity there are two exceptions to this closed communications model:

  1. When we need more than one item of information returned by the function
  2. When a copy of an argument cannot reasonably or correctly be made (example: file stream objects).

These exceptions are handled by parameter passing by reference instead of passing a value. The item passed is called a reference variable and it represents a concept of an alias for the variable. Any change made to the reference variable is actually performed on the variable that it represents. The symbol of the ampersand is used to designate the reference variable (and it is associated with the address operator).

Parameter passing by reference

// prototype void process_values(int qty_dimes, int qty_quarters, double&value_dimes, double&value_quarters); // variable definitionsint dimes = 45; int quarters = 33;double value_dimes; double value_quarters;// somewhere in the function main process_values(dimes, quarters, value_dimes, value_quarters);// definition of the function void process_values(int qty_dimes, int qty_quarters, double&value_dimes, double&value_quarters); {value_dimes = dimes * 0.10; value_quarters = quarters * 0.25;}

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The ampersand must appear in both the prototype and the function definition but it does not appear in the function call.

The above example shows the basic mechanics of parameter passing by reference. You should study the demonstration program in conjunction with this module.

Demonstration program in c++

Creating a folder or sub-folder for source code files

Depending on your compiler/IDE, you should decide where to download and store source code files for processing. Prudence dictates that you create these folders as needed prior to downloading source code files. A suggested sub-folder for the Bloodshed Dev-C++ 5 compiler/IDE might be named:

  • Demo_Programs

If you have not done so, please create the folder(s) and/or sub-folder(s) as appropriate.

Download the demo program

Download and store the following file(s) to your storage device in the appropriate folder(s). Following the methods of your compiler/IDE, compile and run the program(s). Study the source code file(s) in conjunction with other learning materials. You may need to right click on the link and select "Save Target As" in order to download the file.

Download from Connexions: Demo_Parameter_Passing.cpp

Definitions

reference variable
Used with parameter passing by reference.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Programming fundamentals - a modular structured approach using c++. OpenStax CNX. Jan 10, 2013 Download for free at http://cnx.org/content/col10621/1.22
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