Programming Week 6 LBSC 690 Information Technology

Software Software models aspects of reality –Input and output represent the state of the world –Software describes how the two are related Examples –Ballistic computations –Google –Microsoft Word

Types of Software Application programs (e.g., Powerpoint) –What you normally think of as a “program’’ Compilers and interpreters –Programs used to write other programs Operating system (e.g., Windows XP) –M anages display, CPU, memory, disk, tape, E mbedded program (e.g., BIOS) –P ermanent software inside some device

Programming Languages Used to specify every detail of the model Special purpose –Able to specify an entire class of models Spreadsheets (Excel,...) Databases (Access, Oracle,...) General purpose –Able to specify any possible model JavaScript, Java, Perl, C, C++,...

History of Programming Machine language –Language that machine can understand Assembly language –Assembler changes names to machine code High-level languages –Compiler/Interpreter translates to machine language –FORTRAN, COBOL, C, C++, Javascript Visual programming language –Visually arrange the interface components –Visual Basic, …

Machine Language Everything is a binary number –Operations –Data For instance ADD first number (21) second number (86)

Assembly Language Symbolic instruction codes and addresses –Symbolic instruction code “ADD” –Symbolic address “SUM1” For instance ADD 21, SUM1

High level Languages Procedural (modular) Programming –Group instructions into meaningful abstractions –C, Pascal, Perl Object oriented programming –Group “data” and “methods” into “objects” –Naturally represents the world around us –C++, Java, JavaScript

Object Models Represent things in the world as “objects” –Simplest objects are “variables” Represented with a name (n, teacher, …) May be assigned a value (n=4, teacher=“Doug”, …) Represent actions with “methods” –Simplest methods are “operations” Represented with a symbol (+, -, *, /, ^, …) “Classes” group objects with methods –Models how kinds of things behave Objects are instances of classes

Basic Data Types Boolean: true, false Number: 5, 9, String: “Hello World”

Operations and Assignments -xreverse the sign of x (negation) 6+5Add 6 and 5 (numeric) “Hello” + “World” Concatenate two strings 2.1 * 3 Multiply two values x++increase value of x by 1 x = 5set the value of x to be 5 x += yx = x + y x *= 5x = x * 5

Statements Simple assignment statements celsius = 5/9 * (f-32) Statements that invoke a method Temperature.toCelsius(104) Return a value from a method return celsius

Methods Reusable code for achieving a single task function toCelsius(f) { celsius = 5/9 * (f-32) return celsius }

Basic Control Structures Sequential Conditional Repetition

Sequential Control Structure a = 2 b = 3 c = a * b

Conditional Selection Control Structure if (gender == “male”) { greeting = “Hello, Sir” } else { greeting = “Hello, Madam” }

Generating Boolean Results x == y true if x and y are equal x != y true if x and y are not equal x > ytrue if x is greater than y x <= y true if x is smaller than or equal to y x && ytrue if both x and y are true x || ytrue if either x or y is true !xtrue if x is false

Repetition Control Structure Program Example 1: n = 1 while ( n <= 10) { document.writeln(n) n++ } Program 2: For (n = 1; n <= 10; n++) { document.writeln(n) }

Arrays A set of elements –For example, the number of days in each month Each element is assigned an index –A number used to refer to that element For example, x[4] is the fifth element (count from zero!) –Arrays and repetitions work naturally together

Programming for the Web Common Gateway Interface (CGI) [Server side] –Forms encode field values into a URL –CGI passes field values to a Perl program –Program generates a web page as a response JavaScript [Client-side, interpreted] –Human-readable “source code” sent to the browser –Web browser runs the program Java applets [Client-side, compiled] –Machine-readable “bytecode” sent to browser –Web browser runs the program

JavaScript My first script document.write("Hello, world!") Try it at

Handling Events Events: –actions that users perform while visiting the page –Embedded in modern GUI Use event handlers to response events –Event handlers triggered by events –Examples of event handlers in Javascript onMouseover: the mouse moved over an object onMouseout: the mouse moved off an object onClick: the user clicked on an object

Hands On: Adopt a JavaScript Program Launch a Web browser – See how it behaves if you are 13 (or 65) View source and read the program Save a local copy Make some changes and see how it works

JavaScript Resources Google “javascript” –Tutorials: to learn to write programs –Code: to do things you want to do Engineering and Physical Sciences Library –Books in locked case near circulation desk

Aural Perception We respond to sounds without prior focus –Lack of focus limits simultaneous stimuli Absolute amplitude & pitch hard to interpret –But changes stand out clearly Stereo effect provides a sense of direction –Relative amplitude, phase difference

Speech Output Replay of digitized speech clips –High fidelity, but limited vocabulary Speech Synthesis –Generate spoken output from unrestricted input Based on pronunciation rules and lists of exceptions –Sounds unnatural due to misplaced emphasis Prosody-guided speech synthesis –Use pronunciation of similar words as a guide

Auditory Display Nonspeech audio output for user interfaces Same objectives as graphical output: –Alert the user to exceptional conditions –Provide ubiquitous feedback –Present information But different characteristics –Effective even without focus –Fairly low resolution

Auditory Display Design Need a metaphor –Clock ticking, alarm bells, keyboard clicks, etc. Channel is easily overloaded –Focus helps manage cognitive load Changes are more useful than values –Pitch, amplitude, position, harmonics, etc.

An Auditory Image Display Display 2-D images using only sound –Sweep from left to right every second Audible pause and click between sweeps –Top pixels are high frequency, bottom are low Blind users can detect objects and motion –Time indicates horizontal position –Pitch indicates vertical position –Sweep-to-sweep differences indicate motion

Interactive Voice Response Systems Operate without graphical interfaces –Hands-free operation (e.g., driving) –Telephone access Built on three technologies –Speech recognition (input) –Text-to-speech (output) –Dialog management (control) Example: TellMe ( TELL)

Dialogue Management User initiative System initiative –Allows a smaller vocabulary Mixed initiative (e.g., barge in)

Interaction Design Where are you departing from? Where do you want to go? What day do you want to travel? VerificationGoodbye Wrong Confirmed Baltimore National Dulles San Francisco Oakland San Jose Anywhere else Day when there are flights Not a day Sorry Another day Anywhere else

Evaluation Measures Time to learn Speed of performance Error rate Retention over time Subjective satisfaction

Evaluation Approaches Extrinsic vs. intrinsic Formative vs. summative Human subjects vs. simulated users Deductive vs. abductive

Summary HCI design starts with user needs + abilities –Users have a wide range of both Users must understand their tools –And these tools can learn about their user! Many techniques are available –Direct manipulation, languages, menus, etc. –Choosing the right technique is important LBSC 795 in Spring 2006 has this focus