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

Questions?

Course structure Concepts “Turtle”

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

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

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

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

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

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

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

Do this Repeat 2 times: stand clap sit

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

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

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

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

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

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

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.

“Homework”