PROGRAMMING We create identity 1

INTRODUCTION

The course Lecture Tuesdays 10:45 to 12:30

Tutorial Thursday 8:45 to 12:30 or Fridays 12:45 to 17:30

Blackboard

Textbook: Learning Processing, by Daniel Shiffman

INTRODUCTION

The people Lecturers Ansgar Fehnker (Coordinator) Angelika Mader Marcus Gerhold

Student Assistants Margot Rutgers Oliver Horst Carmen Burghardt Thijs Dortmann Marrit Schellekens Wybe Westra Dennis Vinke Lukas Bos

INTRODUCTION

The students

NASA High Speed Flight Station "Computer Room", Dryden Flight Research Center, 1949

COMPUTING

PresenterPresentation NotesThis is NASA's compter room in the late 1949.Where is the computer? Computer referred until the mid 21st century to humansThey performed calculations.Often followed simple instructions to perform one step in a bigger project.

From: Grier, D.A.; , "The Math Tables Project of the work projects administration: the reluctant start of the computing era," Annals of the History of Computing, IEEE , vol.20, no.3, pp.33-50, Jul-Sep 1998

COMPUTING

PresenterPresentation Notes An example worksheet of the "Math Tables" projectA large project to compute for tables of higher mathematical functions for science and administration.These tables (logarithmic tables) were distributed like dictionaries. The Math Tables project was also employed to compute ballistic trajectories in WWII.

COMPUTING

From: Grier, D.A.; , "The Math Tables Project of the work projects administration: the reluctant start of the computing era," Annals of the History of Computing, IEEE , vol.20, no.3, pp.33-50, Jul-Sep 1998

PresenterPresentation NotesComputing projects were giant undertakingsDifferent task to be performed by different groupsComputingSpecial computing Machine operatorsTypistsClerksBookbindersSupervisors and planning Note, it was a government project.

Need for mechanization.

COMPUTERS

Glen Beck (background) and Betty Snyder (foreground) with ENIAC, 1947 to 1955

PresenterPresentation NotesThe first computer were large machines using first switches, then tubes, later transistors.

They could be "programmed" to perform scientific computations.

"Programming" meant to reconnect the wires of the machine, to suit the task.

"Programming" a computer could take several days.

Planning of the rewiring even weeks or months.

UNIVERSAL TURING MACHINE

Turing's insight:

"It is possible to invent a single machine which can be used to compute any computable sequence.

If this machine U is supplied with a tape on the beginning of which is written the S.D ["standard description"] of some computing machine M, then U will compute the same sequence as M."

Turing 1936

PresenterPresentation NotesThe first insight: Whatever is computable by mechanical means, can be computed by a Turing Machine.Many have tried to disprove this conjecture. They proposed "better" computing machines.All of them have been shown to be equivalent to (or less) to a Turing Machine. The second insight:Whatever you can do with a computer, you can do with a programmable computer.No need to rewire. Use a program (what Turing called "S.D.").Invention of "software".

STORED PROGRAM COMPUTER

EDVAC, 1949

PresenterPresentation NotesTuring idea shaped the ideas of "Stored Program Computers".The program is an input, just like the data. The program is data.Programming determines what a computer does.No wires on the outside necessary.

PROGRAMMING LANGUAGES

Evolution of programming languages

Go to http://www.digibarn.com/collections/posters/tongues/ComputerLanguagesChart-med.png for a full-size copy of this chart.

PresenterPresentation NotesProcessing is only one of many programming languages.

There are many others, some extinct by now, other stil alive, and a few new ones that a growing quickly.

Processing is a dialect of Java, which itself draws on previous languages such a C, C++, and Simula.

http://www.digibarn.com/collections/posters/tongues/ComputerLanguagesChart-med.png

PROGRAMMING

PresenterPresentation NotesThis course teaches you "programming".It  teaches how to start  with a description of a problem, and how to arrive at a solution.It teaches the fundamental concepts of programming.It teaches you how to do it well, safe, and responsibly. 

PROCESSING LANGUAGE

PROCESSING LANGUAGE

Aim and purpose

For electronic arts, new media, and visual design

A dialect of Java

Designed by Casey Reas and Benjamin Fry

Popularized by Processing Foundation (Reas, Fry and Shiffman)

Textbook and additional material Learning Processing (Shiffman)

https://processing.org/http://learningprocessing.com/

SETUP AND DRAW

Setup

This method gets executed once Use it to setup the canvas Use it to create shared data structure Use it for everything you want to do at the

beginning

Draw

This method will be repeated as long as the program runs Use it to deal with interaction and animation

SETUP AND DRAW

Setup

This method gets executed once Use it to setup the canvas Use it to create shared data structure Use it for everything you want to do at the

beginning

Draw

This method will be repeated as long as the program runs Use it to deal with interaction and animation

• mousePressed, called when mouse is pressed• KeyPressed, called when a key is pressed

Other standard methods

VARIABLES

Predefined

mouseX, mouseY pmouseX, pmouseY width, height keyCode keyPressed mousePressed mouseButton

Basic Types

int float double (rarely used in processing) bool char

VARIABLE DECLARTIONS

A variable is used to store information. It can contain one piece of information at a time.

Creating a variable is called declaring a variable.

When declaring variables, the programmer specifies the type of information to be stored.

The compiler will set aside that space in memory and give it the name we choose.

Initialization is putting a value into a variable when the variable is created.

Initialization is not required. But usually a good idea.

PresenterPresentation NotesWhen you declare a variable the ‘name’ with be used for the memory.

Now you can use ‘name’ for the content. You do not need to know the machine code name of the memory location. The compiler does it for you.

The book uses “definition”. It is however more common to call it “declaration”.

VARIABLE DECLARATION

int numSegments;

type

name – use a nice meaningful

one

VARIABLE DECLARATION

int numSegments = 5;

type

name – use a nice meaningful

one

intitialisation

DATATYPES

There are different types of data.

Every variable contains only data of one type.

Common basic types

int integers ….,-1,0,1,2, ….

float floating point numbers 1.0, 3.14, -2.1

char characters a,b,c,…, A,B,C,…,!,@,#,$,...

boolean true and false

PresenterPresentation NotesThere is also a type ‘float’ for floating point numbers. More about this next week.

LITERALS

Literals are specific values used in the program. Like 1, 3.4, true, or ‘z’. They have a type, too. There is for example a difference between

the integer 2

the floating point number 2.0

the character ‘2’.

THE ASSIGNMENT STATEMENT

There is an important difference between a variable definition and an assignment statement:

int numSegments = 6; // Variable definition

...

numSegments = 8; // Assignment statement

The first statement is a declaration of numSegments.

The second statement is an assignment statement.An existing variable’s contents are replaced.

THE ASSIGNMENT STATEMENT

The = in an assignment does not mean the left hand side is equal to the right hand side as it does in math.

= is an instruction to do something:copy the value of the expression on the right

into the variable on the left.

Consider what it would mean, mathematically, to state:

numSegments = numSegments + 2;?

ARITHMETIC

For type float use +, -,*, / with the usual meaning

For type int use +,-,* with the usual meaning.

Division / will be integer division. The result will be integer if numerator and divisor are integer.

Another useful operator is modulo % Computes the remainder of division

Useful for integer values that are bound and repeat.

For other type +,-,*,/ may or may not be defined. Result may be surprising. Check what they mean before using them.

11/4 is 2. Not 2.75.

e.g. 60 minutes

ARITHMETIC

x = (3 + x)*(7 + y) + z;

y = abs(x - z) % 50;

z = (x – y)/2;

computed top to bottom

left of = is variables that gets a new value

right of = the expression to

compute the new value

not all operation

defined for all types

some operations behave different

for different types, e.g.

integer division

VARIABLE NAMES

When you define a variable, you should pick a name that explains its purpose.

For example, it is better to use a descriptive name, such as numSegments,

than a terse name, such as ns.

Use common Java/Processing camelCase style for variables.

You do this for yourself, and your colleagues.

PresenterPresentation NotesA good variable name is not too long, but explains its purpose.

It is common in C++ to use the underscore character _ in the place of blank spaces.

For example page_num would be a name for the page number.

COMMENTS

Comments are explanations for human readers of your code(other programmers).

The compiler ignores comments completely.

float canVolume = 0.355; // Liters in a 12-ounce can

Comment

COMMENTS

Comments can be written in two styles: Single line:

float canVolume = 0.355; // Liters in a 12-ounce can

The compiler ignores everything after // to the end of line

Multiline for longer comments:

/*This program computes the volume (in liters)of a six-pack of soda cans.

*/

CONSTANTS

In Processing you can declare CONSTANTS.

static final int ITEM_SIZE = 20;

Common in Java. Rarely done in Processing.

A good idea, also in Processing

It tells that this value should not/cannot change

It gives an explanatory NAME to a value. Makes code less obscure. Use ALL_CAPS for the name.

Needs initial value

SCOPE

Every pair of curly brackets {} defines a Local Scope. Scopes can be nestedEach variable that is declared exists From the point of declarationUntil the end of the scope

You cannot use a variable outside of its scope.Declarations outside of any {} are in Global Scope.Variables in global scope can be used everywhere.

Which may sound good, but is a bad idea.

a.k.a block

SCOPE

float topX;

float topY;

void setup(){…topX = width/2;topY = height/2;…

}

void draw(){float bottomX;float bottomY;…bottomX = topX + width/10;bottomY = topY + height/10;

…

topX = (topY + 1)% 200;

topY = (topY + 1) % 100;

}

global variables

for shared or persistent

data

local variables

for transient data or values

SCOPE

It is considered good practice to minimize the scope

Few global variables. Except for data that has to be shared. Global constants are ok. Most variables should be local.

Global variables make understanding and debugging difficult.

EXAMPLES

Learning Processing http://learningprocessing.com/exercises/chp03/exercise-03-07-absolute-value http://learningprocessing.com/exercises/chp03/exercise-03-07-absolute-value http://learningprocessing.com/examples/chp03/example-03-06-interactive-zoog http://learningprocessing.com/examples/chp04/example-04-08-zoogvars

http://learningprocessing.com/exercises/chp03/exercise-03-07-absolute-valuehttp://learningprocessing.com/exercises/chp03/exercise-03-07-absolute-valuehttp://learningprocessing.com/examples/chp03/example-03-06-interactive-zooghttp://learningprocessing.com/examples/chp04/example-04-08-zoogvars

STYLE

Programs must be written for people to read, and only incidentally for machines to execute.

- H. Abelson and G. Sussman

STYLE

Great software, likewise, requires a fanatical devotion to beauty.

- Paul Graham

STYLE

A good programUses layout to convey the

structure.Different components are

easily recognized.The code adheres to a given

coding guideline. All output is spelled correctly,

with a proper layout

A poor program The layout is coincidental, It is difficult to identify the

structure. Names are cryptic. No discernible effort. Spelling mistakes, poorly

formatting of output.

STYLE

Make yourself familiar with professional style guides

Using a good IDE will help to program in style.

They will automatically “fix” many problems in your code.

TOPICS COVERED

Getting Started

Setup and draw

Variables mouseX, mouseY other system variables variable declaration types

Arithmetic

Predefined methods abs, max, delay …

Topics Look for examples Look at manual

Programming as communication Style Naming Comments Constants

ADMIN

Lectures: Tuesday 11:45 to 12:39

Tutorials: Thursdays 8:45 to 12:30 or Friday 12:30 to 17:30

Assessment: Week 4 tutorial project assessed in week 5 (1/10)Multiple choice test (3/10) Final project (6/10)

TUTORIAL ETIQUETTE

The tutorial and lab sessions are there for practicing programming

They are an opportunity to get help and advice or to help and advise

Don’t use the lab time for other purposes (like facebook)

Wastes valuable time for multitasking

It is distracting to you, and others

Creates a poor learning environment

If it turns out that your are using lab time and space for non-related issues, you may be asked to leave.

ADVICE

This is (not) a difficult course… Students who do well do these things

Attend lectures regularly Attend tutorials regularly Including doing prep work before tutorial Keep up with the textbook Ask questions Ask for help

Programming is a practical subject. Besides book knowledge you need to learn by doing.

GOOD LUCK

ProgrammingIntroductionIntroductionIntroductionComputing Computing ComputingComputersUniversal Turing MachineStored Program ComputerProgramming LanguagesProgrammingProcessing LanguageProcessing languageSetup and DrawSetup and DrawVariablesVariable DECLARTIONSVariable DeclarationVariable DeclarationData TypesLiteralsThe Assignment StatementThe Assignment StatementArithmeticArithmeticVariable NamesCommentsCommentsConstantsScopeScopeScopeExamplesStyleStyleStyleStyleTopics COVEREDAdminTutorial EtiquetteAdviceGood Luck