C++ For Physics S. Brisbane Based on original slides I. Miller

1. C++ For Physics S. BrisbaneBased on original slidesI. Miller IT Learning Group

2. What you know already… • Nothing is assumed

3. What you should have • Now: • Setup instructions for the computers in today’s teaching labs • At least the first part of the C++ generic workbook through to chapter 10 • A copy of these slides • The teaching materials are available from: • http://www-pnp.physics.ox.ac.uk/~brisbane/cplusplus_latest/

4. C++ and OOP? Compilers ISO and ANSI Standard C++ Library The Standard Template Library (STL ) Dev-C++/Eclipse Today's Topics First Program Fundamental data types Functions References Overloading functions Classes

5. What is OOP? • Object Oriented Programming • A way of modelling individual objects in the real world • Students • Vehicles • Buildings • ATM’s • etc, etc

6. So, what is OOP? • Natural thinking – making our C++ code do what we expect something to do in real life. • Class • Member functions/methodsrepresent real object - behaviour • Member variables/data membersrepresent real object - state

7. Editor Disk Add source Code Pre-processor Disk Directives allow add contents from ext files or constants Compiler Disk Convert the high level language into object code Linker Disk Link object code to library code & create exec code Memory Load from disk into memory Loader Disk Execution, CPU executes the program CPU Creating a C/C++ program

8. Why Compile? English talk “Add 17 and 9 please” “Johann Strauss” I’m sorry but I don’t understand English just binary talk, 1’s and 0’s. 001010100111 011011000110 100110110011 111100100000 100000111110

9. Why Compile? C++ Talk C O M P I L E R cout<<"Enter the first number: "; cin >>Num1; cout<<"Enter the second number: "; cin >>Num2; cout<<"The two numbers added = "<<Num1 + Num2; Binary Talk Enter the first number: 17 111001101111 001010100111 011011000110 100110110011 111101011111 Enter the second number: 9 The two numbers added = 26 Monitor

10. C++ Compilers • Many and varied • Sun Studio 10 Solaris, Linux • VisualAge C++ Linux • GCC Multi-platform • Microsoft Visual C++ Windows • Cygwin Linux • Dev-C++ Windows • Xcode Apple

11. C++ standard • Specification for the core C++ language • Types • Syntax • In addition to the core language, C++ has the “STL” • Class definitions for standard data structures • Collection of algorithms used to manipulate these and other structures • A compiler should support the standard

12. Compiler Conformance • There is no C++ compiler or library today that implements the Standard perfectly. • GCC >=4.8 is very close. * • Nothing in this course require the extra features introduced in C++11. • *GCC is mostly language-complete, but the standard library is missing a few aspects. • *https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.2011

13. Working environment • I will use an Integrated Development Environment • Concentrate on the language rather than managing the environment • Speed up error checking • Makes creation of some template projects rather straightforward • Use of eclipse as IDE Focus on writing code and not managing code

14. Other Resources • There are other things to think about besides writing code • Manage the various versions of source code, see: • http://www2.physics.ox.ac.uk/it-services/svn-for-beginners • Which libraries and headers to build and include in your program • A tutorial I used to give going into more detail around libraries, objects headers and compilers • Take you through the basics • Finish with creating a small program from scratch that integrates with the root libraries and is managed by a “Makefile” • http://www-pnp.physics.ox.ac.uk/~brisbane/Teaching/Makefiles/index.html

15. Questions so far?

16. First Program #include <iostream> using namespace std; intmain() { intaNum= 0; cin>> n; cout<< “Your number is: ” << n << endl; return 0; }

17. First Program #include <iostream> • Include contents of the header file in the program using namespace std; • cinis standard input stream object of istream class that allows input from keyboard • coutis standard output stream object, output to screen intmain() • In every C++ program, function

18. First Program intaNum= 0; • variable (memory location called aNum) to hold number of type integer (int) << (the stream insertion operator) cout<<“Enter a number:- ”; >> (the stream extraction operator ) cin>> aNum; First program

19. Comments • In C++, any text prefixed with the comment symbol (//) is an instruction to the pre-processor not to include code following the comment in the program. • It acts until the next line break • int main() //This is a comment about main • Multi-line comments use the /* to open a comment and */ to close

20. Basic Types • int//integer • char // ASCII character or 8–bit signed integer • float //single precision floating point number • double //double precision floating point number • bool // boolean – either true of false • unsigned float/int/char unsigned version of the above • void something with no type or return value

21. Basic Control Flow • Sequence • What we have been doing already • Selection • if…else statements • Two possible marks, 49 or 50 stored in score if(condition is true)if(score>50) cout<<“Passed”;cout<<“Passed”; elseelse cout<<“Failed”;cout<<“Failed”;

22. Basic Control Flow • Selection • switch multiple selection statements • Test must be constant integer value, 1, 10, ‘A’, ‘x’. Not 10.56, 5.2. switch (Test) { case1: cout<<“Number1”; break; default: cout<<“NOT Number1”; } IfSwitchproject

23. Basic Control Flow • Repetition • The ‘for’ loop for (i = 1; i<= 5; i++) { do this statement; now do this statement; } • Note: = is an assignment <= is a relational operator == is an equality operator

24. Basic Control Flow • Repetition • while statement while(some condition is true) do the statements; while (counter < 4) { cout<<"Enter mark "; cin >> mark; total = total + mark; counter ++; }

25. Basic Control Flow • Repetition • do…while loop do { statements } while(the condition is true) • do { cout<<“Mark number " <<mark <<endl; mark ++; } while (mark <=10); DoWhile project

26. Functions • Used to encapsulate data and operations • Can simplify coding • Functions for discrete tasks • Not hundreds of lines of code • Compiler only needs to know • Input data • Output data • Functions can be reused

27. Functions • Need a prototype • Tells the compiler what is coming • Return type • Function name • Parameter list (what is being passed in) voidreadChar(); intgetNumber(); doublenumDoubled(int);

28. Functions • Defining a function (no return value) voidreadChar() { char aChar; cout << "Enter a CHARACTER: " ; cin >> aChar; cout << "Character is " << aChar << endl; return; }

29. Functions • Calling a function • With no return type • readChar(); • With return type “int” intreadNumber(); • intmyNum = 0; • myNum = readNumber(); • cout << “The integer returned is “<< myNum; Funcproject

30. Scopes • The syntax { and } means that you are opening and closing a scope. • It is a way of grouping statements together • Variables declared within the scope have no meaning outside the scope • Function scope (most languages have this) • Block scope (java/python programmers beware!) • class scope (later) • File scope (later)

31. Scope • intmyfunction () • { //open ‘function’ scope • if (true ) • { //open if block • intmynumber=10; //declare and initialize //mynumber variable inside the ‘if’ block scope • } //close if block • return mynumber; //error! • } //close funciton scope

32. Questions so far?

33. Functions – passing data • Pass by Value • Copy of value passed to function • Pass by Reference • Address of value passed to function FuncRef project

34. Functions – pass by Value • Function arguments have been passed as value (copy) • Value outside function not changed • intsquareByValue (intnum) • { • return num*num; • } • “num” only exists inside function scope

35. Functions – pass by Reference • Function argument is the address of the variable • Function works with the variable • Value outside function is changed • intsquareByReference(int &numberRef) • { • numberRef *= numberRef; • } • numberRef is passed as a reference to some integer in the calling scope

36. Declaring References • Must be initialised when declared • Cannot be reassigned • int & xRef = z; initialised • int & yRef; not initialised • xRef = &w;  cannot assign • Another c++ context dependency “=“ acts differently at initialization and assignment.

37. Overloading Functions • Two or more functions with the same name • Must have different parameters • Different number • Different kind • Combination of the two • Compiler determines which function to use, depending on the parameters OverloadingFunctions project

38. Classes and Objects • A class is a definition of a compound variable type • An object is an instance of that class • From a student class • Create many objects of type student • Peter Hain • Sarah Jones • Thomas carlyle • Jane Seymour • Create an instance (object) of class student studentPeter; studentSarah;

39. So, what is OOP? • Natural thinking – making our C++ code do what we expect something to do in real life. • Class • Member functions/methodsrepresent real object - behaviour • Member variables/data membersrepresent real object - state

40. Classes and Objects • Member functions • Called by objectName.functionName() Peter.displayName(); Peter.setCourseName(); • Data Members (variables of object) • Member functions used to access the data members • Peter.name;

41. Standard C++ Library • Collection of classes and functions • Result of conformance to ISO standard • Incorporates what was STL • Class definitions for standard data structures • Collection of algorithms used to manipulate these and other structures

42. Operator precedence Note: Abridged version :- Full table in workbook

43. Exercises • Suggested exercises: • Set up working environment for today/next week • The “Getting Started” hand-out • Ex1, Ex2(a+b), Ex3 tasks 1-4, Ex4 • Those new to C/C++ please try to complete at least the starred(*) exercises today: • Ex5*, 6, 7*, 8*, 9*, 10*, 11*, 12*, 13*, • Ex14 task1-3, Ex15 task1, Ex16 task 1, ex17 task2 only, Ex22 T1&2, 23 T1&2 • It doesn’t matter which seat you pick today. Your account settings are automatically shared across all machines • Please sit in the same seat as last week

44. C++ for Physics - Day Two

45. Creating classes Member functions and Data members Access specifiers Function Templates Pointers Interfaces Dynamic memory (a bit) Today’s Topics

46. Reminder, What is OOP? • Object Oriented Programming • A way of modelling individual objects in the real world • Students • Vehicles • Buildings • ATM’s • etc, etc

47. Reminder, what is OOP? • Natural thinking – making our C++ code do what we expect something to do in real life. • Class • Member functions/methodsrepresent real object - behaviour • Member variables/data membersrepresent real object - state

48. Classes and Objects • A class is a definition of a compound variable type • An object is an instance of that class • From a string class • Create many objects of type string • My Address • My Name • Create an instance (object) of class string • stringmyname; • stringmyaddress; • Or your own class ‘student’ i.e. studentpeter;

49. Classes and Inheritance • Allows creation of hierarchy of classes. • Start with abstract ideas • Detail specific classes • Allows reuse of code • Inherit properties • Base and derived classes • Encapsulation of data

50. Inheritance