1. Algorithms 1 (Lecture 2 of CSE1301)
Dr Damian Conway
Room 132, Building 26
(Consult hours on the door)

2. Notice
Thursday 9am-12pm prac in G13 has been moved to 10am-1pm in the same room.
ALLOCATE+ will continue to show 9am, but it actually starts at 10am.
If you need to be in the prac (e.g. Sci/Eng students), allocate yourself into the 9am G13 prac, but turn up at 10am.

3. Topics
Solving problems
Algorithms
Values and variables

4. The Problem-solving Process
How do we solve problems?
We "just do".
Guesswork-and-luck
Trial-and-error
Experience (possibly someone else's)
"Scientifically"

5. The Problem-solving Process
"Doctor, my head hurts"
Analysis
Patient has elevated pressure in anterior parietal lobe.
Problem specification
Design
1. Sterilize cranial saw
2. Anaesthetize patient
3. Remove top of skull
4. Get the big spoon...
5. etc., etc.
Algorithm
Implementation
sterilize(saw, alcohol);
raise_hammer();
lower hammer(fast);
start(saw);
/* etc. etc. */
Program
Compilation
Executable (solution)

6. Algorithm
A set of instructions specifying the steps required to accomplish some task

7. Algorithm Named after: Muhammad ibn Musa al-Khwarizmi
circa AH ( CE)
Wrote books on arithmetic (especially decimal numbers) and algebra

8. Algorithm
Named after: Muhammad ibn Musa al-Khwarizmi

9. Algorithm Examples: A cooking recipe Assembly instructions for a model
The rules of how to play a game
VCR instructions
Description of a martial arts technique
Directions for driving from A to B
A knitting pattern
A car repair manual

10. Algorithm Examples: A cooking recipe Assembly instructions for a model
The rules of how to play a game
VCR instructions
Description of a martial arts technique
Directions for driving from A to B
A knitting pattern
A car repair manual

11. Algorithm
Examples:
Arroz con pollo
Almond and honey slice

12. Components of an algorithm
Variables and values
Instructions
Sequences
Procedures
Selections
Repetitions

13. Values Represent quantities, amounts, or measurements
May be numerical or alphabetic (or other more mysterious things)
Often has a unit related to their purpose
Examples:
Recipe ingredients
Hardware requirements

14. Variables Are containers for values
Places to store values when we're not using them.
May be restricted to containing a specific type of value (i.e. only stores integers)
Examples:
Little black book
Cricket team

15. Reading Deitel & Deitel, C: How to program
Chapter 1, Sections 1.1 to 1.10
Chapter 3, Sections 3.1 to 3.3