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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
References and Pointers in C++

I always know that when I'm running a C Course, the concept of pointers will be one of the more difficult elements for some of the delegates to grasp. No big deal, I can explain them in a number of ways, provide examples from different angle, and we'll be over the hiccough in progress in not too long a time. Pointers provide an exceptionally powerful capability, but C's an old language now and they're not exactly newbie-friendly.

You have C's pointers available in C++, but you also have references ...
* A Pointer is a variable the contains the address of another variable.
* A Reference is an alternative name that's assigned to a variable.

Thus, when you use a pointer, you need to prefix it with a "*" to mean "contents of" and to set it, you need to prefix it with "&" to mean address off, and that's simply not necessary with a reference.

Here's a sample from our C++ Course that displays data from an array using both the pointer way and the reference way:


int weights[] = {96,98,100,99,98,95};
for (int k=0; k < 6 ; k++) {
int &rWeight = weights[k];
int *pWeight = &weights[k];
cout << "rWeight " << rWeight << endl;
cout << "*pWeight " << *pWeight << endl << endl;
}


Do be careful - if you assign something to an existing reference, you're changing the value of the variable that it's aliased to and you're not making the reference point at something else .... but if you assign something to an existing pointer, you're changing what it points to.



(written 2006-07-10)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
C233 - C and C based languages - OO in C++ - beyond the basics
  [801] Simple polymorphism example - C++ - (2006-07-14)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [925] C++ - just beyond the basics. More you can do - (2006-11-14)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1572] C - structs and unions, C++ classes and polymorphism - (2008-03-13)
  [1674] What a lot of files! (C++ / Polymorphism demo) - (2008-06-12)
  [1819] Calling base class constructors - (2008-10-03)
  [2577] Complete teaching example - C++, inheritance, polymorphism - (2010-01-15)
  [2845] Objects and Inheritance in C++ - an easy start - (2010-07-01)
  [3056] C++ - a complete example with polymorphism, and how to split it into project files - (2010-11-16)
  [3123] C++ objects - some short, single file demonstrations - (2011-01-07)
  [3124] C++ - putting the language elements together into a program - (2011-01-08)
  [3142] Private and Public - and things between - (2011-01-22)
  [3244] C and C++ - preprocess, compile, load, run - what each step is for - (2011-04-12)
  [3251] C++ - objects that are based on other objects, saving coding and adding robustness - (2011-04-17)
  [3508] Destructor methods in C++ - a primer - (2011-11-05)
  [3811] Associated Classes - using objects of one class within another - (2012-07-21)
  [3979] Extended and Associated objects - what is the difference - C++ example - (2013-01-18)
  [4356] Object factories in C++, Python, PHP and Perl - (2014-12-19)
  [4375] Final examples for 2014 - and a look at our 2015 training course options - (2014-12-31)
  [4377] Designing a base class and subclasses, and their extension, in C++ - (2015-01-01)
  [4559] When do I use the this keyword in C++? - (2015-10-29)
  [4560] Variables, Pointers and References - C and C++ - (2015-10-29)


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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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