[PPT] - CS 105: Intro to Computing, Non-technical Craig Zilles (Computer PowerPoint Presentation

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CS 105: Intro to Computing, Non-technical

Craig Zilles (Computer Science) January 27, 2020 https://go.illinois.edu/cs105sp20

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To Today

1. Goals of this course (and why)
2. Structure of this course (and why)
3. Some Computer Basics
4. Programming Language & Python Basics
5. Muddiest Points
input/print, types, type conversion, syntax and
ther errors
6. Challenge questions

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Wh What is Comp mputer Science?

“Computers are to Computer Science what telescopes are to astronomy”

Edsger Dijkstra

Computer Science is concerned with understanding:

what is computable,
how to [specify computations, perform computations,

communicate between computers] in the [fastest, most reliable, most secure, cheapest/lowest power] way,

how to help humans solve problems with computers

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Th The lear arning objectives s for this s course se

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Wh What is “Programmi mming”?

A series of instructions that can

be carried out by a computer

A really useful skill for many

people

Useful to even know what is

possible

http://www.programmingbasics.org/en/beginner/img/commands4.png

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Al Altern rnate Term rms

“Programs” “Software” “Application” “Code”

But not "Codes" – it's always singular!

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Pr Programs are eve verywhere

https://openclipart.org/

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Pr Programs do many things

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Th Three par arts s of writing a a program am

Algorithms:

A step-by-step process for achieving a result
Often expressed in pseudo-code (instead of a prog. language)
Avoid distraction of details
Increases generality

Programming:

Expressing commands in a form that the computer

understands Testing and Debugging:

Making sure that the program (always) does what is intended

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Ma Making a Peanut Butter & Jelly Sandwich (a randomly selected student algorithm)

Gather your supplies such as bread, a spreading knife,

peanut butter and jelly.

Spread peanut butter on one slice of bread using the

knife.

Spread Jelly on another slice of bread.
Take the two slices and put them in a sandwich form

with the peanut butter and jelly facing eachother.

Enjoy.

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Na Natural language (English) is too ambiguous

“I saw the man in the park with the telescope”
Who had the telescope?
Who was in the park?

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Step 1) Gather Materials Step 2) Lay the two pieces of bread about 8” apart flat on their faces on your working surface. Step 3) Using the knife, scoop a dollop of peanut butter out of the jar roughly 1” in diameter. Spread the dollop evenly on the face of one slice of bread until there is an even layer of peanut butter roughly 1/8” thick. Step 4) Rinse the excess peanut butter off the Knife. Then dry with towel. Step 5) Repeat Step 3 on the other slice of bread replacing the peanut butter with the jelly or jam. Step 6) Place one slice of bread on the plate, jelly side up. Then place the other slice of bread on top of the slice on the plate peanut butter side down, ensure the shapes of the bread slices match and their edges are flush. Step 7) Enjoy!

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Ke Key Idea: Pr Programming languages are de designe ned d to be be exact and nd una unambi biguo uous us

Everything in a programming language has a precise

form (syntax) and a precise meaning (semantics)

Syntax: Rules of what are acceptable programs
Semantics: Rules specifying what a program does
This need for exactness is challenging for many novices.

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Al Also, thi his stuf uff is totally arbi bitrary!

Computers and programming languages are human

made

There is no reason that you should know any of this

stuff if you haven’t seen it before

People in this class that seem “smarter” have probably

seen it before

The easiest bugs to find in your code are the ones that

you made before

There is no short cut around making mistakes

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St Stru ruct cture of

f t

this c cou

urse
The book
Pre-lecture activities
Lecture
Homework
Labs
Quizzes and Exams
Office Hours & Piazza

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Wh What is known about teaching and learning (1

(1)

1. No one can pay attention for 90 continuous minutes
We’ll have a 5 minute break in the middle of lecture
Please try to focus the rest of the time
2. “Time on task” is a primary factor of how much gets

learned.

My job, give you productive things to spend time on
3. One learns much more by doing than by reading or

listening.

You have to expend mental energy or it doesn’t stick

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4. The things you can most efficiently learn are:
Those related to things that you already know
Those that are only slightly harder than the things you

can currently do

5. Long term retention comes from repeated, distributed(in

time) practice

Retention comes from cycles of forgetting and re-

learning

Spaced in time; cramming doesn’t work for long term

retention

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Wh What is known about teaching and learning (2

(2)

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Gr Growth Mindset

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Te Teaching by diminishing deception

Computers (like many things) are too complicated to

understand all at once.

I’m going to glaze over unnecessary details until we’re

ready for them

Feel free to ask questions, but I might defer some for

after class / during break

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St Stru ruct cture of

f t

this c cou

urse
The book
Pre-lecture activities
Lecture
I clickers, participation encouraged, ask questions,

recorded

Homework
Labs
Quizzes and Exams
Office Hours & Piazza

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We Weekly cycle:

each topic covered over a 1.5 week period
Book activities, Pre-lectures have strict deadlines
Homework has late deadline for 70% credit.
Lecture/Lab allows 2 excused/unexcused absences

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Lecture Th F Sa Su M Tu Th W F Sa Su Read Book (Participation) Pre-Lecture Book (Challenge) Homework Lab

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We Weekly cycle:

22 Lecture Th F Sa Su M Tu Th W F Sa Su Read Book (Participation) Pre-Lecture Book (Challenge) Homework Lab Lecture Read Book (Participation) Pre-Lecture Book (Challenge) Homework Lab M Tu Th W F Sa Su Read Book (Participation) Pre-Lecture

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Th The homework plag agiar arism sm/collab aboration po policy in n CS 105 is:

Ic Iclic licker que question: n: select the he be best ans answer

A) It is okay to hire random internet strangers to do all of your homework for you. B) You must do all of your homework alone (not even TAs can help) C) You can get any help you want as long as you type in the answers D) Students can only discuss the homework at a high level; code must not be shown to other students, but you can ask TAs for help E) Assignments can be done in groups of two students

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Fo Formative vs. Summative Assessment

Practice / Formative Assessment:
Primarily intended for learning, self-evaluation
CS 105: Participation/Challenge, Pre-lecture activities,

Homework

You may get help from anyone, but you have to enter

the solution

Summative Assessment:
An evaluation of how much has been learned
CS 105: Quizzes and Exams
To be done by yourself; you may not get help from

anyone

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Qui Quizzes and nd Exams (al

all to be done by yourself)

Four mid-term exams in the Computer-Based Testing

Facility (CBTF):

Sign-up at https://cbtf.engr.illinois.edu/sched
4-day window: Thursday – Sunday
50 minutes
Four quizzes (basically required practice exams)
50 minutes timed, self-proctored, wherever you want

to take them.

3-day window: Thursday – Saturday
One three-hour final exam in the CBTF

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Anno Announc uncements: see cour urse web b pa page

If you didn’t finish the reading/pre-lecture, deadline

extended to Thurs.

Labs begin this week!
If you didn’t get checked off in Lab last week:
Get checked off for it at the end of lab
You can sign up for the first exam now
We’re going to give up to 2% extra credit for the ~20

students that have the most Piazza answers marked as good answers.

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Com Computer b r basics: m : major p

r part

rts

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"I had difficulty understanding computer components such as memory and storage."

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Mo Modern CPUs like those in laptops, ta tablets, and phones execute how many in instructio ions per second:

Ic Iclicker que question: n: se select the he be best ans answer

A) Thousands B) Millions C) Billions D) Trillions E) Quadrillions

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Com Computers a are:

Ic Iclicker que question: n: se select the he be best ans answer

A) Smart B) Not smart

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Co Computers run very low-le level l in instructio ions

Things like:
Move a number from one storage location to another
Add two numbers together
Check if one number is larger than another
Go to a different place in the code
Computers can be programmed at this level, but
It is very tedious and error prone
You have to write a lot of code to do anything

significant

This code isn’t portable across different processor

types (e.g., laptops vs phones)

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Hi High gh-le level l Lan anguag ages (& Pyth thon)

HLLs: productive, safer, portable
Python: very useful language, gentle learning curve
Once you learn one language, much easier to learn
thers (same concepts)
Python2 vs. Python3
Interpreted language
Three ways to run the Python interpreter (at least)
Interpreter, Jupyter notebook, and running scripts

from the command line

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(In In Python) x + y is is:

Ic Iclicker que question: n: se select the he be best ans answer

a) an assignment b) a statement c) a variable d) an expression e) a comment

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Py Python values have ve types

"The most confusing part of this weeks reading

assignment was the difference between string and

integer. "
We’ve met two kinds so far:
Strings: e.g., our string literals like “Hello CS 105!”
Integers: whole numbers of arbitrary precision
You can ask a value what its type is using:

type(expression)

You can convert between them with str() and int()
It is important that you keep track of the types of your

values!

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A E D C B

Wh Where does Python run on the comp mputer?

Ic Iclic licker que question: n: se select the he be best ans nswer

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Th The input() fu function gets user input

Can take a string as an argument to be used as a prompt
Returns a string
I am having a hard time differentiating between the use
f int(), input() and/or int(input())

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The The print() func function

Assuming there is a variable value with the value 7,

which of the following statements prints: count = 7 A) print(“count =” value) B) print(“count =”, end=“value”) C) print(“count =”, value) D) print(“count =” + value) E) print(“count = $value”)

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