Win32 Programming Lesson 3: C++ Refresher

Before We Begin  You can call the Win32 APIs in a lot of different languages (Visual J++, Visual Basic.NET, C#) but we’ll be using C++  Lower-level language, closer to the metal  Don’t mix up Managed C++ with Unmanaged (at least for now!)  Don’t be upset if this all feels basic to you; the class will pick up speed next week

C++ History  Based on the name, we might want to remember C; developed by K&R.  C had one goal: to write operating systems  Downside: procedure-oriented  Then came the OO “revolution”  Added classes (and a number of other features) to C and called it C++ Quiz: shouldn’t it be ++C (and what’s the difference?

Classes  Perhaps the most important difference in C++ is the ability to create Classes, just like in Java (only faster ;)  We’ll cover that on Thursday

Today – everything else  First, we’ll begin with “hello world” #include “stdafx.h” #include int _tmain(int argc, _TCHAR* argv[]) { std::cout << "Hello world" << std::endl; return 0; }

Style  You’ve either got it or you’re going to get it  Style starts with commenting code  Single line: /* Comment */ Or: // Comment  Multi-line: /* * Multi-line comment */

Declarations  Also useful to comment  And name intelligently  Hungarian Notation? See: url=/library/en- us/dnvs600/html/HungaNotat.asp url=/library/en- us/dnvs600/html/HungaNotat.asp int iMyCounter; // index for counting through array…

Layout  C++ doesn’t care about indentations…  But I do.  Indenting code makes it readable: if (total <0) { std::cout << “You owe nothing\n”; } else { std::cout << “You owe ” << total << endl; } Clarity (story)

Writing Good Code  You start by deciding what it is you want to write  So many programmers here at FIT start by opening up Visual Studio  I start programming on a whiteboard

Common C++ gotcha  Variable assignment: Variable = Expression  Variable comparison: Variable == Expression  int iData_list[3] Has valid members 0-2 Remember, real programmers count from zero

Scope  Beware of scope errors…  int total; int count; int main() { total = 0; count = 0; { int count; count = 12345; } ++count; return(0); }

Namespaces  Remember I keep using std::cout to print?  That is because the cout variable is part of the std namespace  There’s lots to know about namespaces… for this class, recognize the using keyword using namespace std; What is the downside of this?

References  Ahh, approaching the dreaded pointer  But I promise that pointers really are very simple – once you understand them  Let’s look at some code

Pass by Value  #include void inc_counter(int counter) { ++counter; } int main() { int a_count = 0; inc_counter(a_count); std::cout << a_count << “\n”; return(0); }

Pass by Reference  #include void inc_counter(int& counter) { ++counter; } int main() { int a_count = 0; inc_counter(a_count); std::cout << a_count << “\n”; return(0); }  Beware the “dangling reference”… you’ll see

Pass by Reference – Pt 2  #include void inc_counter(int *counter) { ++(*counter); } int main() { int a_count = 0; inc_counter(&a_count); std::cout << a_count << “\n”; return(0); }  Beware the “dangling reference”… you’ll see

Structures and Unions  A simple way of grouping things together  Used in the Win32 APIs a great deal, so you better get comfortable with them!  struct structure-name { member-type member-name; // Comment member-type member-name; // Comment … };  A union is similar, but members overlap

Pointers  “There are things, and there are pointers to things…”  A thing, we already know about… like an int… This consists of a chunk of memory of particular size  However, we can also create a pointer to something, like a pointer to an int This consists of a value which “points to” (stores the memory location of) a thing in memory. It doesn’t create the thing in memory.

Consider  int thing; // Define “thing” int *piThing; // Create a pointer to an int thing = 4; // Put the value for in thing piThing = &thing; // & == Address of… *piThing = 5; // thing now equals five  * is the dereference operator (the thing pointed to)  & is the address operator (the address of)

Practical Example  Imagine this struct: struct foo { std::string name; std:string instrument; std::string city; int skill_level; } mylist[LENGTH];  How can we sort mylist most effectively? Write me some p-code…

Classic Example  Command line arguments… int main(int argc, char *argv[]) argc is the number of arguments on the command line argv contains the arguments; it’s a pointer to an array…

Dangling Reference Example  int *iFunc() { int x;... return &x; } main() { int a = *iFunc(); }

Next Class  Simple Object Refresher, and Assignment 1