Introduction to the Course

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1 Introduction to the Course Nick Maclaren courses/cplusplus Some of the slides in this lecture are the copyright of Bjarne Stroustrup, but they are not marked specially

2 Acknowledgement We are grateful for Bjarne Stroustrup for making his source materials available, and this course is based on them. Their copyright remains with Bjarne Stroustrup. You may use them only when doing this course; for other purposes, the originals are available from his Web site, under his (liberal) conditions. 2

3 This lecture This first lecture is mostly my (nmm's) material, because this course is intended for a very different audience and a somewhat different purpose, but I have included some of Bjarne Stroustrup's slides, which remain his copyright. I have tried to not misrepresent Bjarne Stroustrup's views when editing those slides, but may have made a mistake and done so. You must look at his original first lecture slides to see what he really said. Additional material in subsequent lectures has been marked (nmm) to distinguish it. 3

4 Abstract Here, we ll outline the aims for this course and present a rough course plan. Finally, we ll present the simplest possible C++ program and outline how it can be made into running code. 4

5 Overview Course aims and outline Programming Hello, world! Compilation 5

6 This is a course In Programming For beginners in C++ who want to become professionals i.e., people who can produce reliable and portable software who are assumed to be bright Though not (necessarily) geniuses who are willing to work hard Though do need sleep occasionally Using the C++ programming language 6

7 The Original Aims Teach/learn Fundamental programming concepts Key useful techniques Basic Standard C++ facilities After the course, you ll be able to Write small colloquial C++ programs Read much larger programs Learn the basics of many other languages by yourself Proceed with an advanced C++ programming course After the course, you will not (yet) be An expert programmer A C++ language expert An expert user of advanced libraries 7

8 The Aims (Cambridge) Very much the same, but also very different The target audience is graduates who have done some programming (say, in Python), not undergraduates who have done none It is assumed to be academics who want to program, not people who want to become programming professionals It is being given in half the time the book recommends for newcomers to programming But not just physical scientists, or even engineers Equally relevant to biologists, social scientists, and the scientific work of the arts and humanities The mathematics is elementary but, for example, you do need to know what matrices are 8

9 The Aims (cont) After the course, you ll also be able to Write serious and efficient scientific and other programs using simplistic but functional C++ Know something about the difficult areas around what you are using and why not to go there After the course, you will not (yet) be Someone who knows how to optimise C++ for HPC (high performance programming) Someone who knows how to use C++ for parallel programming (except perhaps for very simple MPI) An expert on C++ :-) 9

10 What This Course is NOT It is not C++ for CVs or Simple Recipes in C++ Simple Recipes in C++ Such courses teach you just enough to get into trouble You often need to unlearn them before going further The C Subset of C++ It is not C C with a C++ Flavour or The C Subset of C++ You then get all of the disadvantages of C C is a high-level, semi-portable assembler It is not C++ for C Programmers or C++ for Computer Scientists C++ for Computer Scientists Knowing C is not an advantage It teaches practical use, not programming for its own sake C++ for Microsoft Windows It is not C++ under Linux or C++ for Microsoft Windows Most of it will work on any system 10

11 Why this course? It ain't what you don't know that causes the trouble; it's what you know for sure that ain't so. Probably first said by either Josh Billings or Samuel Clemens (Mark Twain) This is the cause of 80% of hard-to-solve problems when using C and C++ - that figure is based on experience with user's problems Most books, Web pages and courses teach you how to use the facilities but not how to avoid problems Bjarne Stroustrup's course is much better Often things work fine when you are following recipes, but blow up when you need to do something very slightly different this course teaches understanding not recipes 11

12 Why this course? (cont) Scientific programmers aren't computer scientists This book and course are better oriented for scientists than most many others are useful only for ''computer science'' purposes It has been selected and extended to help with that There were a lot of useful materials Including these lectures Also the author didn't impose impossible constraints on their use, as some commercial ones do I found this course fairly ''natural'' My own courses also concentrate on good programming practice and writing reliable and portable code 12

13 Key to Success The key to success is ''Thinking in C++ terms'' And not just in by using ''object orientation'' etc. The main way is in the choice of which way to write code And that is precisely what this course teaches It was also written by the designer of the language Not just someone who thinks he understands C++ I have learnt a huge amount from working through it 13

14 The Problem C++ is a huge language, by any standards ISO Fortran 90 is 253 pages; Fortran 2003 is 422 pages ISO C++98 is 680, and C++03 is 709, but that is deceptive They include a lot of C90 by reference (176 pages) The library section is underspecified, and has few examples, though you need only a little of it Realistically, C++ is over 3 times as complicated as Fortran, with over 10 times as many ambiguities and 'gotchas' gotchas' This makes it much harder to learn There is just no comparison with Pascal, Python etc. 14

15 So Just Learn a Subset? You can't learn every wrinkle of the whole language The same is true of every powerful language The first problem is selecting a subset to learn And the second is staying within that subset Every book and course uses its own preferred subset That also applies to every large program It makes it extremely hard to read other people's code It is easy to make errors when working on such code Not all constructs work in all circumstances 15

16 Other C++ Courses Several other people give C++ courses at Cambridge University They are all shorter, but not necessarily easier Your understanding will be pro rata to your effort Their focus is different, and they may not be open to everyone check first Computer Laboratory (8 lectures) Engineering There isn't a simple reference, and the courses are very specialised if relevant, check them out And others. 16

17 Beware of Recipes! C++ is not a good language to learn from recipes You rarely want to follow a recipe exactly,, and even a simple change may cause weird failures Worse, a recipe may work when you are testing it but not when you put it into actual use Even worse, an apparently unrelated change (possibly even in the standard library) can cause such failures There is no substitute for understanding the language And this course teaches understanding, not recipes! 17

18 Towards a Solution Learning C++ takes time there is no magic bullet The book advises 210 hours' work, for complete newcomers That might be whole days for the target audience We are aiming for 12 afternoons of lecturing Even a specially targetted course would be 10 days And I am not convinced that would be enough :-( No other CS course exceeds 3 whole days 18

19 Towards a Solution We are trying a different approach There will be 12 afternoons of lecturing These will be followed by a practical class There will also be some assistance by and (by arrangement) telephone We also hope to experiment with desktop conferencing for such assistance You will need to do a lot of practical work on your own This includes reading the book and doing the drills and exercises If you genuinely know the material, and can do the exercises, it is reasonable to skip a lecture and practical class 19

20 Prerequisites It is critical to know what this course covers ''Unix: Introduction to the Command Line Interface'' If you don't, you will have trouble even getting started And you must be able to use a Unix plain text editor (e.g. emacs, gedit, pico or vi) If you want to use a Microsoft or Macintosh system, you need the equivalent skills But you won't be able to get much help with them It may also make it trickier to get help in the practical classes 20

21 Prerequisites Unless you are already a programmer, you are very strongly advised to attend this first ''Python: Introduction for Absolute Beginners'' ''Programmer'' does not mean Visual Basic, Excel or even most uses of Matlab It means Python, Fortran, C, Pascal etc. There is more that you need, but not until Chapter 12 21

22 Corequisites Not needed before you start, though it helps You need to know them before you finish And you will need them for real programming ''Building, installing and running software'' ''How Computers Handle Numbers'' There are a lot more that will or may be useful Some are mentioned later, when relevant See See notes/unix courses 22

23 The Author Bjarne Stroustrup The Book Course Reference Programming Principles and Practice Using C++ Addison-Wesley 2009, ISBN The Web Site The known mistakes (fixed in the second printing) 23

24 The Local Site Local Materials notes/unix courses/cplusplus Modified versions of these lecture slides, containing important extra information (Slightly bug-fixed) sources of the FLTK toolkit and course headers The answers I wrote to many of the drills and exercises (incomplete and probably buggy) And possibly other relevant files 24

25 The Problem The biggest problem with teaching the use of C and C++ is correcting false beliefs (''unteaching'') Why? It ain't what you don't know that causes the trouble; it's what you know for sure that ain't so. The languages are solid with arcane 'gotchas' gotchas' Most people hit them, often, and hack around them They often make wrong deductions, and tell others They even write books and Web pages based on such false beliefs :-( I really do mean that such misbeliefs are the cause of the majority of the nastiest bugs in C and C++ 25

26 The Means Starting Buy the book you will need your own copy Start reading the book, in chapter order After each chapter, review all of the Terms, and check you know what they mean At least starting with chapter 3, do the TRY THIS sections and drills Use only the facilities taught up to that point to do them Why? The course teaches a particular approach to C++ that will lead to portable and reliable code 26

27 The Means (cont) But please be honest with yourself Do not skip the drills and exercises, even if you are sure that you don't need to do them Use only the facilities taught up to that point to do them they are intended to teach specific points Do at least a third of them 'for real', including all of them that you are even slightly unsure about Don't skip any exercises that look as if they might need something introduced in the chapter As soon as you start to have trouble, or even before, attend the practical classes 27

28 Moving on The Means (cont) Read the chapters and review the Terms ahead of the next lecture Do the drills, before starting the exercises Read the chapters again after each lecture Ask about any problems in the practical classes Then complete doing all of the drills and exercises that you are in the slightest doubt about Ask for any other advice on C++ or programming Feedback is welcome (typos, suggestions, etc.) 28

29 Using the MCS (a.k.a.( PWF) You need to apply for a MCS account for Linux Do that at Computing Service Reception You will need to download and build the materials There are full instructions and a script to do that You can log in remotely (that's what I do) ssh <MCSid>@linux.pwf.cam.ac.uk You can't use SSH keys to login, unfortunately I don't recommend using the Microsoft system There is no supported C++ system 29

30 Using Your Own Computer You do not n need d to use the MCS You can use a departmental system You can use your own desktop or laptop You will have to install the materials yourself They have build scripts for Linux (both the MCS and generic) The base course has them for Microsoft, but I have not tested them, and you may need to merge in my fixes For other systems, you may need help (but I can advise only in generic terms) 30

31 System and Compiler You can use anything plausible Linux, Macintosh and Microsoft are all suitable, and so are many other systems you won't have heard of gcc (g++ g++), Intel icpc,, Sun/Oracle Studio, Microsoft Visual Studio and any many other compilers are all fine But you will have to install them yourself! The practical classes will use g++ under Linux You will need an MCS account You will need to download and built the materials yourself (which should be trivial) 31

32 Beyond the Course The author has written several books, including: The C++ Programming Language Addison-Wesley 1997, ISBN It is in a similar style, but covers much more, is much more concise, but still covers nowhere near the whole language It is for experienced programmers only and, even so, doing its exercises are still essential to understanding it We give many other relevant courses I give several on practical program design, Fortran, parallel programming etc. 32

33 Beyond the Course C++ is the hardest language to learn that I have met I have used over a hundred, and been an expert on a dozen I usually learn from the language standard I don't find it hard to use it's avoiding the gotchas that is the problem It isn't always easy to distinguish between A simple bug in your program When you are using the wrong construct for a task A restriction of your compiler or a library Something that C++ doesn't make possible 33

34 Rough course outline Part I: The basics Types, variables, strings, console I/O, computations, errors Vectors, classes, functions, source files Part II: Input and Output File I/O, I/O streams Graphical output Graphical User Interface Part III: Data structures and algorithms Free store, pointers, and arrays Lists, maps, sorting and searching, vectors, templates String handling More details on scientific uses 34

35 Rough course outline (cont.) Throughout Program design and development techniques C++ language features Background and related fields, topics, and languages Practical points related to real scientific programming Information about portability, reliability etc. 35

36 Planned Schedule All of these use the programming tasks as a way of teaching C++ in a realistic context. Do not skip a lecture because you don't need the facility, but only if you can do all of the drills and exercises using only the facilities taught so far. Note that the first session is the only one that will be repeated and the only one that is not followed by a practical class There is no point in attending both repetitions Introduction and basics session 1 Chapters 1 and 2: Programming and ''Hello World'' Chapter 3: Objects, Types and Values 36

37 Planned Schedule (cont.) Computation and Errors session 2 Chapter 4: Computation Chapter 5: Errors It is very important to read these carefully, and do many of the drills and exercises 'for real', even if you think they are easy, as they teach the subset of C++ being used in this course Writing a program session 3 Chapter 6: Writing a program Chapter 7: Completing a program The techniques taught are also useful for decoding non-trivial data formats, as are commonly used as input to scientific programs; in the book, they are used as a way of introducing some more C++ concepts, and as getting practice in using the language as it is taught 37

38 Planned Schedule (cont.) Even if you know some C++, and can do the previous exercises, you are recommended to start attending lectures here, as there is a significant increase in complexity at this stage Functions and classes session 4 Chapter 8: Technicalities: Functions, etc. Chapter 9: Technicalities: Classes, etc. Existing C++ programmers need to pay special attention to the second lecture, as it teaches a particular way of using classes, but both lectures are important 38

39 Planned Schedule (cont.) Basics of C++ input/output session 5 Chapter 10: Input/Output streams Chapter 11: Customizing I/O 'Chapter 11a': Other Approaches to I/O These covers the basics of what most programmers need to know about text (i.e. human-readable) I/O in C++ I have extended it with warnings about what you can assume safely, once you start to need the non-trivial I/O usage and files needed for real scientific programming 39

40 Planned Schedule (cont.) Graphics - lectures 6 and 7 Chapter 12: A Display Model Chapter 13: Graphics Classes Chapter 14: Graphics Class Design Chapter 15: Graphing Functions and Data Graphics is useful in itself, but the book uses it mainly for how to use classes, so it is important to do these even if you will never use graphics Chapter 12 is mainly practice in using previous techniques, so can be covered fairly quickly Chapters 13 and 14 teach several major new class facilities, so read them and do the exercises thoroughly doing their exercises and drills is important,, especially in chapter 14 Chapter 15 introduces how to use function and default arguments, and I have extended it slightly to cover simple numerical coding 40

41 Planned Schedule (cont.) Graphical User Interfaces (omitted) Chapter 16 will be omitted, but the chapter is still worth reading as an introduction to GUIs There is no need to do the drills and exercises, unless you need to use GUI interfaces or callback functions in parallel code But please note that chapter 16 is an introduction only,, and does not describe any of the fundamental problems with modern GUI designs; understanding those is critical to writing even half-decent GUI interfaces. In particular, event delivery is seriously misdesigned at a fundamental level, leading to FOUL race conditions, even if you try to defend yourself against them. If you want to know the techno-political history that led to this sorry situation, please ask I was peripherally involved with several aspects of it, as well as knowing a few areas in depth 41

42 Planned Schedule (cont.) Memory, Arrays, Vectors and Matrices - lectures 8 and 9 Chapter 17: Vector and Free Store Chapter 18: Vectors and Arrays Chapter 19: Vector, Template and Exceptions Other libraries with array facilities This covers the basics of what most programmers need to know about using arrays and pointers in simple ways in C++ The STL and other libraries lecture 10 Chapter 20: Containers and Iterators Chapter 21: Algorithms and Maps Some more on other libraries This covers the basics of the design and use of the STL 42

43 Planned Schedule (cont.) Ideals and History (omitted) Chapter 22 will be omitted, but you are strongly advised to read it, especially what it says about ideals See also later remarks under Testing Text Manipulation (omitted) Chapter 23 will be omitted; if you need to do any non-trivial text manipulation, you are strongly advised to read it, and do the drills and exercises If you want to use regular expressions, I give a course on them, but do this chapter first Numerics etc. - lectures 11 and 12 I (nmm) haven't yet decided what to put here, as it will depend on how much I haven't covered earlier 43

44 Planned Schedule (cont.) Embedded System Programming (omitted) Chapter 25 will be omitted, but it is relevant to advanced HPC programming; you may want to read it later Testing (omitted) Chapter 26 will be omitted, but you are strongly advised to read it The CS course How to Help Programs Debug Themselves includes some more details on how to do this effectively The C Programming Language (omitted) Chapter 27 will be omitted Note that this is one area where I (nmm) disagree with Bjarne Stroustrup; there are much more serious problem areas in C than the ones he describes (which are still serious) You are strongly advised to be very cautious when using the C subset of C++, which includes any of the headers like <cstdlib>, <ctype>, <cmath> and so on 44

45 Promises Detail: : We will try to explain every construct used in this course in sufficient detail for real understanding There is no magic Utility: : We will try to explain only useful concepts, constructs, and techniques We will not try to explain every obscure detail Completeness: : The concepts, constructs, and techniques can be used in combination to construct useful programs There are, of course, many useful concepts, constructs, and techniques beyond what is taught here 45

46 More Promises Realism: : the concepts, constructs, and techniques can be used to build industrial strength programs i.e., they have been used to Simplicity: : The examples used are among the simplest realistic ones that illustrate the concepts, constructs, and techniques Your exercises and projects will provide more complex examples Scalability: : The concepts, constructs, and techniques can be used to construct large, reliable, and efficient programs i.e., they have been used to Reliability and portability: (nmm) I have added quite a lot of warnings about problems that you may encounter later when you write real applications (especially in HPC) Just note them and remember not to push the boundaries too far You won't (or shouldn't) encounter them while doing the exercises 46

47 Feedback request Please mail questions and constructive comments to scientific Please fill in a feedback form Other feedback would also be appreciated On style, contents, detail, examples, clarity, conceptual problems, exercises, missing information, depth, etc. Book support website ( Local site ( ( notes/unix courses/cplusplus) 47

48 A first program just the guts // int main() // main() is where a C++ program starts { cout << "Hello, world!\n"; // output the 13 characters Hello, world! // followed by a new line return 0; // return a value indicating success } // quotes delimit a string literal // NOTE: smart quotes // so make sure your quotes are of the style " " // \n is a notation for a new line quotes will cause compiler problems. 48

49 // a first program: A first program complete #include "std_lib_facilities.h" // get the library facilities needed for now int main() // main() is where a C++ program starts { cout << "Hello, world!\n"; // output the 13 characters Hello, world! // followed by a new line return 0; // return a value indicating success } // note the semicolons; they terminate statements // curly brackets { } group statements into a block // main( ) is a function that takes no arguments ( ) // and returns an int (integer value) to indicate success or failure 49

50 Hello, world! Hello world is a very important program Its purpose is to help you get used to your tools Compiler Program development environment Program execution environment Type in the program carefully After you get it to work, please make a few mistakes to see how the tools respond; for example Forget the header Forget to terminate the string Misspell return (e.g. retrun) Forget a semicolon Forget { or } 50

51 The next lecture Will talk about types, values, variables, declarations, simple input and output, very simple computations, and type safety. Now let's take a look at the local support site 51

Chapters 1 & 2 Programming and Programs

Chapters 1 & 2 Programming and Programs Instructor: Dr. Hyunyoung Lee Based on slides by Dr. Bjarne Stroustrup www.stroustrup.com/programming Abstract Today, we ll outline the aims for this course and