91074 – Algorithm Languages and User Interfaces

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91074 – Algorithm Languages and User Interfaces. Sorting: Bubble Sort, Selection Sort, Insertion Sort, Quick Sort. Comparisons, Cost of an Algorithm. Contents. Sorting Algorithms Informal Instructions, Algorithms and Programs High and Low Level Languages Translating Between Languages

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### 91074 – Algorithm Languages and User Interfaces

Sorting: Bubble Sort, Selection Sort, Insertion Sort, Quick Sort. Comparisons, Cost of an Algorithm.

Contents
• Sorting Algorithms
• Informal Instructions, Algorithms and Programs
• High and Low Level Languages
• Translating Between Languages
• User Interfaces

### Sorting Algorithms

Sorting: Bubble Sort, Selection Sort, Insertion Sort, Quick Sort. Comparisons, Cost of an Algorithm.

Activity
• In groups, sort a small number of cards numerically
• New Rules: only allowed to look at two cards at a time, only allowed to swap two, no other moves.
Notes

Sorting Algorithms: There are lots of ways computers sort lists. In this course we will look at Bubble sort, Selection Sort, Insertion Sort and Quick Sort.

Cost of an Algorithm: For sorting giant lists (like a phone book) on a computer, speed is important. We call this the ‘cost of the algorithm’ and we measure it by how many comparisons the algorithm has to make for a set list size.

Bubble Sort Instructions
• Compare the first two
• If out of order swap them
• Look at the next two,
• Repeat Steps 2 and 3 until the (new) end of the list.
• Repeat steps 1 – 4 until the list is sorted

Called Bubble Sort because like bubbles in a glass, the next one makes it way to the top

Bubble Sort Cost

E4E: Formula?

Example Bubble Sort Video

Bubble Sort and Cost Video (sorting by height)

Selection Sort
• Compare the first two and find the biggest
• Then compare the biggest with the next one
• Remember which is the (new) biggest
• Repeat steps 2 and 3 until the end
• Swap the biggest one with the (new) last one
• Repeat steps 1 to 5 until the list sorted

Called Selection, because you are selecting the biggest one and swapping it to the end.

Selection Sort Cost

E4E: Formula?

Insertion Sort
• Compare the first two, and put them in order in a new list
• Insert the next item into the right place in the new list by comparing it with each item until you find it’s place.
• Repeat step 2 until the new list is sorted, and the old list is empty.

Called Insertion, because you’re inserting into the correct position in a new list.

Insertion Sort Cost

E4E: Formula?

Quick Sort (pivot)
• Select the next (first) item and make it a pivot
• Compare each item with the pivot, creating a list of smaller items and a list of bigger items.
• Repeat steps 1 and 2 for each sublist, until the list is sorted

Is one of a group of “divide and conquer” sorting algorithms

Called Pivot, because you separate the list into smaller lists based on a pivot.

Quick Sort Cost

E4E4E: Formula?

Some Comparisons

Which one is fastest, which is second fastest?Sorting lists of 20

Bubble Selection Insertion Quick

Click to see them race

Some Comparisons

Which one is fastest, which is second fastest?Sorting lists of 20

Bubble Selection Insertion Quick

Some Comparisons

Bubble Sort vs Quick Sort (Youtube) Lists of 30 coloured blocks, Comparing swaps, not Comparisons

• Which has the least comparisons?
• Which has the least swaps?
• Is comparisons or swaps the best way to measure “Cost of Algorithm?”
Comparing Sorting Comparisons

Part A) Pick a sort, and six items. Step by step talk through sorting six items. E.g Carrot, Apple, Grape, Banana, Eggplant, Feijoa, - compare Carrot and Apple. (Out of order, so swap)

• Compare Carrot and Grape (in order)
• Compare Grape and …

Part B) Do an insertion sort for 5, 6, 7 and 8 items, recording the cost.

Part C) Explain how you calculated the cost and say why that is the cost.

Getting sort data quickly

http://www.mundayweb.com/progs/applets/saas/Or search “MundaySaas”

http://www.sorting-algorithms.com/Has eight common sorts

### Informal Instructions Algorithms and Programs

Their Characteristics and Roles

Algorithm Notes
• An algorithm is a precise unambiguous specification of how to accomplish some computational task in a finite number of well-defined steps.
• An algorithm is distinct from a computer program.
• An algorithmhas a cost (the number of steps it will perform) for a task.
• Different algorithms for the same task may have different costs.
Informal Instructions, Algorithms and Programs

Informal Instructions: Vague, Imprecise, easy to read/create, interpreted many ways

May have: gaps, bad spelling, incomplete

Form: oral or written,

Algorithms: Precise, single task, has inputs/outputs, made up of steps, has a cost,

Form: code, flow chart, text

When are they used (Roles)Informal Instructions, Algorithms, & Programs

Informal Instructions: Humans, communication, ease,

Algorithms: code, computer, part /functions in prog,

Programs: a variety of functions, self contained

Programming Concepts

Informal Instructions:

Algorithms:

Programs:

### High and Low Level Languages

Characteristics

High and Low Level Languages Video

Low Level Languages Machine Code (1GL)
• 1st Generation Language (1GL)
• Numbering system called “Binary”
• Also called “Machine Code”
• The only way to Program computers in the 1960s and 70s
• Old Explanation of Binary (before 3GL)
Low Level Languages Machine Code (1GL)

Flight of the Conchords

• Binary Solo

Big Bang Theory

• Chuck Norris of Numbers
• Palindrome = Reverse , 1001001  1001001
Low Level Languages Machine Code (1GL)

Characteristics

• Lowest Level Language
• Very Hard for humans to understand
• Very slow to create code
• No abstraction: Human knows exactly what’s going on
• Directly interacting with hardware
• Doesn’t need translating or compiling
• Native Language of Computer
Low Level Languages Assembly (2GL)
• 2nd Generation Language (2GL)
• One step up from Binary/Machine code
• Has functions like Move (MOV), Compare (CMP), Increment (INC), Jump(JMP)
• Uses Hexadecimal (like web colours #ffffff )
• Has no Compound functions like “If (this, then do this)” or “Loop (3 times)”
• At the end it is “Assembled” into Binary
• Used when you need exact control over code (e.g very small microchip, efficient code needed)
Low Level Languages Assembly (2GL)

Assembler Example

Hello World

Ignore music and second half

“The main problem with “assembler” jokes is, they are difficult to read”— scapegrace

Low Level Languages Assembly (2GL)

Characteristics

• Second Lowest Level Language
• Hard for humans to understand
• Slow to create code
• Little abstraction: Human knows almost exactly what’s going on
• Needs Assembling into Binary / Machine Code / 1GL translating or
High Level Languages (3GL)

Common Programming Languages

Like Basic, C, Java, C# and Scratch

High Level Languages (3GL)

Features

• Easier to Read and Write (and maintain)
• Portable across different CPU families
• Written as Text
• Many High Level Languages, each with their own Syntax
High Level Languages (3GL)

Brief History of 3GLs

• 1957 Fortran (punch cards)
• 1964 Basic  MS Visual Basic
• 1972 C (text colouring)  C++
• 1995 Java (Object Oriented)
• 2001 C# (OO, components)
• 2007 Scratch (Drag n Drop)
High Level Languages (3GL)

Characteristics

• High Level Language
• Lots of Abstraction into easily readable code
• Easy for humans to understand
• Quick to create code
• Needs Translating into Machine code
HighLevel Languages (4GL)

Lots of Abstraction

High Level Languages (4GL)

Features

• Flow charts and modules
• 4GL creates the code for you
• Often for a specific task e.g Managing a tax database
High Level Languages (4GL)

Characteristics

• Examples: Ruby on Rails, Oracle, Powerbuilder
• High Level Language
• Lots of Abstraction sometimes not even looking at code
• Very Quick to create code
• Needs Translating into Machine code

“All 4GLs are designed to reduce programming effort, the time it takes to develop software, and the cost of software development. They are not always successful in this task, sometimes resulting in inelegant and unmaintainable code.” (wikipedia)

Low and High Levels

Invention of High Level Languages (3GL)

High Level and Translators

• 1983 Educational Cartoon

BASIC

Java

C

### Translating between High and Low Level Languages

Compilers, and Interpreters

Translating (Compiling) Video

Translating between Levels

Why do we need to Translate high level languages into low ones?

• Because Binary is the only language the computer understands
• Creates precise code rather than abstract
• So code is portable
Translating between Levels

Interpreters and Compilerson Planet Gooble De Gook

Two types of Translator

• CompilersDo the whole program at once at the endCan save program down as an .exe file
• InterpretersTranslate the whole program one line at a timeCan cause errors or refuse to run

### User Interfaces

Heuristics

User Interface Video

Mr Bell’s New Home Nightmare

Accidentally open Garage door

Mr Bell’s New Home Nightmare

Door bell is locked behind front door

User Interfaces

We measure the usability of a user interface through a series of tests called “Heuristics”.

What is a User Interface?/ What is a User Interface’s role?

• Communication between user and computer/machine
• Makes the program do what user wants it to
• Inputs like, Button, key, wheel, mouse, handle, Switch,
• Outputs like, lights, sound, speakers, visual, screen, heat, display
• Manages/ Controls interactions
Heuristics (tests for User Interfaces)
• Visibility of system status
• Match between system and the real world
• User control and freedom
• Consistency and standards
• Error prevention
• Recognition rather than recall
• Flexibility and efficiency of use
• Aesthetic and minimalist design
• Help users recognize, diagnose, and recover from errors
• Help and documentation

Look these up online – JakobNeilsenmade them up.

User Interfaces

50 different things that have a user interface

Playstation, Door, Computer, Toaster, Phone, Drill, Bike, Car, Clock, Gun, Printer, Office Chair, Distortion pedal, Ipod, TV, Stereo, Projector, Websites, lightbulb, Scissors, Pen, Power Plug, Window, Air Conditioning, Curtain, Fridge, Stove, Watch, Jacket zip, car jack, shoe, toilet, shower, cap, tap, tack, cat door, badge, earring, glasses,

Potato peeler, Cheese Grater, knitting needles, sewing machine, watter bottle, knife, vhs, can opener, Milk bottle, Towel, chop sticks, light, calculator, filing cabinet, Microwave, elevator,

.

User Interfaces