High School level (years 9-10 in Australia, ages 14-16) introduction to programming course, based on the language Processing, includes class material, exercises, examples, and tests. Course ran for 2 terms in 2014. Feel free to use as is, borrow ideas, etc.

1. Introduction to Programming
Class 1
Paul Brebner
Paul.Brebner@nicta.com.au
CTO Performance Assurance Pty Ltd

2. Notes
• Slides, exercises, example programs, etc for an Introductory
High School Programming Elective (Years 9 and 10)
• No prior experience assumed
• Ran for 2 school terms
• Required 1 computer per 2 students, a computer and
projector for the presenter
• Based on the language Processing, www.processing.org
• Each class was about 1.5 hours long, included talk and
supervised exercises, there was also another 45 minute
class per week which was just for practical exercises
• Assumes that there is reasonable IT support, that students
can download and run things from the internet, and that
they can save, share, and load programs

3. Who am I?
• Computer Scientist
– Study of computers and computing
– The theory of computing
• What is a
– Programmer? Software Architect? Software
Engineer? IT person?
• History of computers (mine)

4. Colossus – 70 years old, 1st programmable
electronic (valve) computer

5. “My” computers
• 1978, Burroughs B6700, > $1M
• Mainframe Bank computer with “punch cards”

6. 2 = Card reader

7. First home made
• Mini-scamp microcomputer – 1979, $200
• Microprocessor (Computer on a single chip)
• 256 Bytes RAM, 1MHz CPU, Input = switches,
output = LEDs

8. VAX 11/780 (1980)

9. VAX specs
• 1MByte RAM (Core memory)
• 1MHz CPU, $250,000, lots of circuit boards

10. Home designed & made
• 1984
• $1,000, 64KBytes RAM
• 6809 CPU (2 MHz)
• 8” floppy disc
• Programmed for
– music synthesiser

11. Amiga 500
• Game machine!
– 1987, $1,000
– 0.5MByte RAM
– 7MHz CPU
– Colour graphics and sound
– Mouse
– 3.5 inch floppy disk

13. Intel 486
• 1993, homebuilt, 50MHz CPU, $3,000

14. Basic computer architecture
Address 0
Address 1
Address 2
Address 3
MEMORY
CPU
BUS
Address 100
Address 101
DISPLAY
1 FETCH
PC
IR 2 DECODE
3 EXECUTE
LOADR1
LOADR2
STORE
ADDER
END
Registers
R1
R2

15. Simulation game
• Everyone has a role:
– Fetch
– Decode
– Execute
• LOADR1, LOADR2, STORE, ADDER, END
– BUS
– MEMORY
– DISPLAY
• Explain Registers and roles

16. Simulation
• Here’s the program in “binary”
– 0101
– 1000
– 0110
– 100
– 1010
– 0101
– 1001
– 1101
– 1010
– 1111

17. Simulation: What will it do? Displays
two characters...
• Here’s the program in “English” (some hidden)
– LOADR1
– ?
– LOADR2
– 100
– STORE
– LOADR1
– ?
– INCR2
– STORE
– END

19. Problem!
• Machine code programs
– In binary – too hard to read/write
– Hard to write large (> 1000 lines?) programs
– Only processes binary numbers – what about decimals?
text? Images?
– Error prone
– Not portable – every CPU type has a different instruction
set, have to rewrite the program for every CPU type.
– Solution
• High level programming languages
– E.g. Fortran, COBOL, LISP, Prolog, Pascal, C, C++, C#, Java, Javascript,
Processing

20. High level languages
• High level programming language
– e.g. Print(“hi”)
– Translated (Compiled) into machine code
– Or run on a “Virtual machine”
– Java “write once, run everywhere”
• Runs on a JVM (Java Virtual Machine).
• Can run on anything from a mobile phone to a super-
computer
– “Processing” – a high level graphics language
running on top of Java!

21. Processing layers
• Processing
– Runs on
• Java
– Runs on
• JVM
– Runs on
• Actual CPU

22. Lines of Code
• How big are programs? 1 LOC – 100M LOC
• How many lines of code a day is normal?
– 10 LOC a day per programmer (famous figure)
– As programs get bigger it gets harder to get them to work correctly
• Programming includes other critical tasks
– Management (planning for what needs doing when by who)
– Specification (what should the program do?)
– Design (how should the program do it?)
– Programming (writing the program)
– Reviewing (reading the program – often someone else’s program – to check it)
– Integration (getting your part of the program working with other parts)
– Testing (does the program do what is should do? Does it have bugs?)
– Debugging (getting rid of the bugs – no program is ever bug free)
– Deployment (putting the program where it needs to be to run)
– Maintenance (keeping it running, upgrading it)
– Retirement (removing the program once it is no longer needed)
– Documentation (describing how the program works so someone else can understand it)

28. Processing Example: Patterns
// Move the mouse around. The faster you go the bigger the ellipse
// This is a COMMENT
// Primitive processing function: setup() is called once to create screen size and colour
void setup() {
size(640, 360);
background(102);
}
// Primitive processing function: draw() repeats forever
void draw() {
variableEllipse(mouseX, mouseY, pmouseX, pmouseY);
}
// a new function! draws a LARGER ellipse the fasterrrrrrrrrrrrrrrr the mouse speed
// speed is computed as the distance between current and previous positions
void variableEllipse(int x, int y, int px, int py) {
float speed = abs(x-px) + abs(y-py);
stroke(speed); // primitive – sets the drawing colour (float type = white to black)
ellipse(x, y, speed, speed); // primitive – draws an oval at position x, y, and height and width
}