01 Introduction

The Speaker The Course Introduction Development Workflow

1. Introduction

June 7, 2010

1. Introduction

Introduction to C/C++, Tobias Weinzierl page 1 of 27


Outline

The Speaker The Course

Concept Calendar Literature

The Introduction What is a computer?

von-Neuman architecture What is a high-level language?

bytecode, intermediatelanguages, and the real world

Where does it all come from?historic overview & the softwarecrisis

The Development Workflow:Tools and Activities

1. Introduction



1.1. The Speaker

Excerp From my CV

19971999 Ringeisen Gymnasium Ursberg:3D software renderer (Pascal/C)

June 2000October 2000 sd&m AG, Munich:Stock exchange (C++)

March 2001September 2001 Chair of Systems & Software Engineering:Ubungen zur Einfuhrung in die Informatik(Java)

September 2002February 2003 sd&m AG, Munich:Financial services (Java)TUMLots of Mathematics and Scientific Computing

July 2009 Ph.D. DefenseA Framework for Parallel PDE Solvers onMultiscale Adaptive Cartesian Grids (C++)

October 2009now KAUST-TUM Scientific Project ManagerPeano frameworkSoftware Engineering, coding best practices,and domain-specific languages inHigh Performance Computing

1. Introduction



The Scientific Workflowan Iterative Scheme

Modelling NumericalTreatment Design of

Software

Implementation

NumericalExperiments

Postprocessing

Visualisation Tests

1. Introduction



Scientific Software Crisis

PITAC report 2005

PITAC report 2005: TodaysCSE ecosystem is unbalan-ced, with a software basethat is inadequate to keeppace with and support evol-ving hardware and applicati-on needs.

It is consequently of uttermost importanceto have skilled and trained programmers.Programming comprises both a craft and anart, and, hence, coding is not just an unim-portant task which can be left to less intel-ligent henchmen.

1. Introduction



However . . .

PITAC report 2005: Todays CSE ecosystem is unbalanced, witha software base that is inadequate to keep pace with and supportevolving hardware and application needs.

It is consequently of uttermost importance to have skilled and trained programmers.Programming comprises both a craft and an art, and, hence, coding is not just anunimportant task which can be left to less intelligent henchmen.

Almost everybody almost all the time: I agree but in my caseits different. I have better/more urgent things to do than to thinkabout software as, before, I have to understand the underlyingphysical/technological/medical principles.

1. Introduction



A Success StorySorry About the Sarcasm

Nature 447: In 2006, data from the array led a team of scientiststo the surprising conclusion that the worlds oceans had cooledduring 2003 exceptionally warm years in terms of global surfacetemperature. The team published its findings in Geophysical Re-search Letters[1]. Such apparent cooling was seized on by peo-ple keen to highlight the uncertainties in forecasts of global war-ming[2].That cooling has now been shown to be an artefact. In someof the buoys they are manufactured in separate batches asoftware glitch caused the temperature and salinity data to beassociated with the wrong depths. When the problem data areexcluded from the analysis, the cooling trend drops below thelevel of statistical significance. (pp. 7140)

http://www5.in.tum.de/~huckle/bugse.html

1. Introduction



1.2. The Course

Concept

Through C/C++ in a rush Programming means training

course cant replace it

Provide a deeper understanding ofunderlying mechanisms

Three slots a 45 minutes per day Provide some exercises Provide some programming support

1. Introduction



After the Course

Temple Church, London

Through C/C++ in a rush Programming means training

course cant replace it

Provide a deeper understanding ofunderlying mechanisms

Content is tailored to Ph.D. students(not undergrads)

Content is aligned with scientificsoftware

Three slots a 45 minutes per day Provide some exercises Provide some programming support

1. Introduction



Callendar

Monday, June 7, 3 slots, 9:3010:15, 10:3011:15, 11:3012:15 Tuesday, June 8, 2 slots, 10:3011:15, 11:3012:15 Wednesday, June 9, 3 slots, 9:3010:15, 10:3011:15, 11:3012:15 Thursday, June 10, 3 slots, 9:3010:15, 10:3011:15, 11:3012:15 Friday, June 11, 3 slots, 9:3010:15, 10:3011:15, 11:3012:15 Monday, June 14, 3 slots, 9:3010:15, 10:3011:15, 11:3012:15 Tuesday, June 15, 2 slots, 10:3011:15, 11:3012:15 Wednesday, June 16, 3 slots, 9:30-10:15, 10:3011:15, 11:3012:15 Thursday, June 17, 2 slots, 9:3010:15, 10:3011:15

I provide an additional hour programming support each day after the lectures. OnTuesday, the lectures start later as I have to do another lecture before. If I dont stay atthe lecture room after the course for the programming support, feel free to write me anemail ([email protected]).

1. Introduction



Literature

Martin Fowler: Refactoring Erich Gamma, Richard Helm, Ralph Johnson, John M. Vlissides. Design Patterns:

Elements of Reusable Software Randall Hyde: Write Great Code I: Understanding the machine Randall Hyde: Write Great Code II: Thinking Low-level, Writing High-level Scott Meyers. Effective C++ Scott Meyers. More Effective C++ Walter Savitch. Absolute C++ Bjarne Stroustrup. The C++ Programming Language

1. Introduction



1.3. Introduction

A Turing Machine

MemoryALU

IO

If we wanna handle a car/machine(efficiently), we have to know how itworks. That doesnt mean that wehave to be able to construct acar/machine ourselves.

Computer (von-Neumannarchitecture): ALU, Memory, IOController, Bus

Processor (Very) simple binary operations

such as add, increment, . . . Takes one or two numbers,

combines them, and writes backresult to memory

Has a program counter holdingone number

Memory

1. Introduction



Memory

Memory

ALU

IO

21:22;23;24; 425; 526;27;28:





Memory Long linear sequence of post its

(storage locations) Sequence of storage locations

holds natural numbers Storage locations are

enumerated Example: Add entry 24 and entry

25 and write result back to entry21

1. Introduction



A First Machine Code

Memory

ALU

IO

21:22;23;24; 425; 526;27;28:



combines them, and writesback result to memory


Memory Long linear sequence of post its

(storage locations) Sequence of storage locations

holds natural numbers Storage locations are

enumerated Example: Add entry 24 and entry

25 and write result back to entry21

1. Introduction



Program Counter

Memory

ALU 21:22;23;24; 425; 526;27;28:

113: add114; 24115; 25116; 21

PC: 113





Memory Computer program is a sequence

of natural numbers Each number equals command

(code) Program counter tells ALU which

command to execute next Program counter incremented

after each command Random access memory

machineRAM machine

1. Introduction



Instruction Streams

Memory

ALU 21:22;23;24; 425; 526;27;28:

113: add114; 24115; 25116; 21

PC: 113

Properties of machine instructions Code, i.e. number-to-command

mapping, is machine-specific Set of available commands is

machine-specific Constraints on codes (which

codes are allowed when) aremachine-specific

Performance of a command ismachine-specific

Writing machine code Cumbersome (small number of

directives) Error-prone Not portable

We need a more abstract program description (programming language).

1. Introduction



Translation Concepts

Algorithm

Machine Code Intermediate Code

To be done for each architectureSell/give it to the customerInstall it on the computer

To be done once

Compiler(Translator)

Compiler(Translator)

Machine Code

Interpreter(Simultan Translator)

Sell/give it to the customerInstall it on the computer

1. Introduction



A Compiler . . .

. . . is a big translation table, i.e. a = 4; b = 5; c = a + b becomes

move4to 24move5to 25add2425to 21

. . . does all the management and linearisation of the memory stream . . . provides more abstract commands than the machine language can do . . . manages the program counter . . . and does a lot more

Each real computer scientist has to invent at least one new language and write thecorresponding compiler once in his/her lifetime!

1. Introduction



History of C

Origins (1970s) Zoo of languages & compilers Among them A and B (Ken Thompson, invented UNIX) Use to write operating systems

History of C 1972, Dennis M. Ritchie, Bell Laboratories, AT&T 1973/74, Brian W. Kernighan Purpose: Write operating systems and compilers

Fundamental concepts of C Powerful to write an operation system Small number of commands Structuredness (no sequences of assembler code)

State of C Used to write UNIX General purpose language Available on all UNIX systems

1. Introduction



History of C++

Bjarne Stroustrup

Software Crisis (80s) Complex systems, difficult to

maintain Lack of abstraction Lack of modelling facilities

Smalltalk and the OOP History of C++

early 80s, Bjarne Stroustrup, BellLaboratories, AT&T

extension of C, i.e. C programsare C++ programs

with new ideas of OOP

1. Introduction



C++State of the Art?

Memory

ALU 21:22;23;24; 425; 526;27;28:

113: add114; 24115; 25116; 21

PC: 113

Popular languages such as Java or C#are C ++

They now adopt concepts of C++formerly deprecated

New paradigms are discussed, buthave to stand the test of time

Next generation C++0x is not yetreleased

Many application areas (in particularHPC and Scientific Computing) havenot yet fully adopted and understoodOOP and C++

This course teaches C++ from scratch. However, it does not follow the historic pathneither does it start directly with sophisticated OOP concepts. It rather follows theacademic path, i.e. introduces one fundamental concept at a time. As OOP (as aconcept) still is considered to be sophisticated in our disciplines, it will be the last thingwe talk about.

1. Introduction



1.4. Development Workflow

Three Tools Coin Our Work

Editor (vi, Emacs) to write simple textfiles

Compiler (g++) invoked on thecommand line

Linker (g++) invoked on the commandline

1. Introduction



If Programming Were Cooking . . .

Editor (vi, Emacs). . . we would write down with the editorthe recipe of one single dish such asthe dessert or the main course. Therecipe then is the algorithm and it iswritten down as source code which istypically a simple text file with theextensions .c, .cpp, and so forth.

Compiler (g++) Linker (g++)

1. Introduction




Editor (vi, Emacs) Compiler (g++)

. . . would take the recipe (sourcecode) and cook it. The results arecalled object code or object files. Theytypically have the extension .o. It isinvoked by g++ -c filename.c.

Linker (g++)

1. Introduction




Editor (vi, Emacs) Compiler (g++) Linker (g++)

. . . would take the individual dishesand combine them into a completemeal with several courses. It isinvoked by g++ filename1.ofilename2.o -o outputfile andproduces an executable.

. . . there would be a menu card given by several header text files as well. They typicallyhave the extension .h or .hpp.

1. Introduction



Standard Workflow

Write down your source codes (files file1.cpp, file2.cpp, ...) into text fileswith an editor of your choice

Write down your descriptions (files file1.h, file2.h, ...) (we will do this lateras it is a matter of style) into text files with an editor of your choice

Open your command line and typeg++ -c file1.cpp . produces file1.og++ -c file2.cpp . produces file2.og++ file1.o file2.o myappl . produces executable myappl./myappl . execute myappl

1. Introduction



Exercise

vi first-appl.cpp

# inc lude i n t main ( ) {s td : : cout

01 Introduction

Documents

tobias weinzierl page

software basethat

thinkabout software

witha software base

scientific computingjuly

sdm ag

trained programmers

coding best practices