1. Nate Brunelle Today: Pseudo-Code, Party
CS1110
Nate Brunelle
Today: Pseudo-Code, Party

2. Questions?

3. Course structure
Concepts
“Turtle”

4. Ambiguity “Put the pot in the dishwasher”
What we say to computers: Instructions
How to wash your hair?
How to wash your hair:
Lather
rinse
repeat

5. How to wash you hair: repeat: lather rinse Lather Repeat:

6. How to wash you hair: repeat 3 times: lather rinse How to lather: wet your hair put shampoo in your hand repeat until hair is foamy: rub your hand through you hair

7. Pseudo-Code Code: write things in a way a computer can understand
Pseudo- Not quite
Pseudo-Code:
Not quit write so that a computer can understand
Good for expressing things unambiguously
But still using English to gloss over the details

8. Conditionals What if I’m out of shampoo? How to wash hair:
if you are out of shampoo:
get more shampoo
repeat:
lather
rinse

9. Rules of Pseudo-Code
Sequence = Do the highest line first, then perform them in order from top to bottom
Line = one “thing” to do
Repetition = repeat something
Fixed number of times : e.g. “repeat 3 times”
Until something happens: e.g. “until hair is foamy”
Conditions/Decisions = maybe do something
Check something first
If there is no more shampoo, then get more
Named actions = two parts: definition, use
Definition = how to do a thing
Use = when to do the thing defined

10. Party
Repeat 2 times: Sing “Happy Birthday to you” Sing “Happy Birthday to Nathan” Sing “Happy Birthday to You” Clap

11. Do this
Repeat 2 times: stand clap sit

12. Brush your teeth
Write pseudo-code instructions for brushing your teeth
Share with your neighbor, who will try to find a problem with it
Remember:
Sequence
Repetition
Conditionals
Named Actions

13. 3x+1
Let x be your age in years let count start as 0 Repeat as long as x is not 1: add 1 to count if x is even: divide x by 2 otherwise: multiply x by 3 and add 1 Clap “the count” many times

14. Variables In Math: In Statistics: In Programming:
A name that refers to a particular value
In Statistics:
A name for a thing that has one value, but we don’t know what it is
In Programming:
A named value that can vary over the course of doing something
x is a variable in the previous slide

15. Problem Programs cannot “reflect” on what they did
Let x be your age in years
Let “count” = 0
Repeat as long as x is not 1:
add 1 to “count”
if x is even:
divide x by 2
otherwise:
multiply x by 3 and add 1
Clap “count” many times

16. Bugs Syntax Semantic Logical Understandability
Statement does not “parse”
Semantic
Grammatically correct, but nonsense
Logical
Means something, but not what you meant
Understandability
I said it, it makes sense, and it means what I meant, but no one else can understand it

17. Syntax Semantic Statement does not “parse”
Dog of by chicken for running video the
W202dkdljdkla9**ls
Semantic
Grammatically correct, but nonsense
Colorless green ideas sleep furiously
Park your car upon the cloud.
3  0

18. Logical Understandability Means something, but not what you meant
“double 5” vs “5+2”
Understandability
I said it, it makes sense, and it means what I meant, but no one else can understand it
The sign should have dashes between fish and and and and and and and and and chips.
Prandial soleation is gauche.

19. “Homework”