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Go to Moodle and Take Quiz 2

Opens at 9:30

Time: 8 minutes

Password:

Comp 118: Introduction to Programming

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EDUCATION IS WHAT REMAINS

AFTER you have FORGOTTEN

everything that you LEARNED IN SCHOOL

Wisdom of the Day

Real school is the school of life

Be a lifelong learner

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Weather News

2025 4th warmest year in U.S. history was full of deadly weather extremes

https://www.climatecentral.org/climate-matters/2025-in-review-us-temperatures

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Globally, 2025 was the 3rd warmest on record, after 2023 and 2024

https://www.ecmwf.int/en/about/media-centre/news/2025/2025-third-warmest-year

Global temp in 2025 was only marginally (0.01°C) cooler than 2023, and 0.13°C cooler than 2024, which remains the warmest year on record.
Last three years were three warmest on record, WMO confirms
Average temperature has exceeded 1.5 C for longest period on record
Paris accord temperature goal could be breached this decade

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Heat Wave Fuels Massive Wildfire In Australia

Temperatures rose as much as 34 degrees above average in Victoria, Australia, where wildfires have already destroyed 750,000 acres and more 100 homes and buildings.

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Lessons from Weather/Climate

Look at the big picture
Don’t be fooled by local and temporary conditions
Don’t be selfish
We are all connected
Poor countries suffer more but nobody is immune
The earth is burning, boiling, and sinking both physically and spiritually
We are destroying the planet and the humanity

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Class Norms

https://docs.google.com/document/d/1kaooyF2U1JpqbACbTlxTVbfxhhgjkanAAMeAzPl4fpY/edit?usp=sharing

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Looking Ahead

First History Essay is due Mon, Jan 19 (midnight)
First set of CodeLab exercises due Thu, Jan 22 (midnight).
Lab 0 due Sun, Jan 25 (midnight)
MSSC schedule will be announced soon

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Reminders

No make-up for quizzes
AI not allowed
For labs, do not use anything we have not learned in class. If you do, you will be required to give an oral explanation of your code

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Today’s Agenda

Quick logistics review: course website,Moodle, textbook, CodeLab, onlineGDB
POGIL activity on Intro to Python.

Go to https://csits.kenyon.edu/

Come back and go over as a group
Discuss some general concepts about programming
For next Tuesday, read sections 2.1-2.7 in the textbook
Quiz 3 will include questions from today and next reading

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Main Goal of the Course

Learn algorithmic and computational modes of thinking
Introduction to the art of computational problem solving
Learn basic principles and elements of programming in the context of two important languages

https://runestone.academy/ns/books/published/KenyonComp118Sp26/GeneralIntro/intro-TheWayoftheProgram.html

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Topics

Python Programming
C++ Programming
Algorithm Design
Debugging
Good programming Practices

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The Python programming language

Python is an example of a high-level language; other high-level languages you might have heard of are C, C++,C#, Java, Pascal, PHP, and many more …
The machine actually executes a low-level language. This is machine code, the actual language of the hardware.
There must be a special program to convert the high-level code into something the machine can execute:

Interpreter - a (low-level) program that reads the high-level code and interpretes it, executing it line by line, alternately reading lines and performing computations. This is what Python does.
Compiler - a program that translates the entire high-level language code into low-level language code that the machine can execute. This is how C++ works.

Which way would be faster?

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Compiler

Convert entire program to machine code
Execute machine code on cpu

Source code (program)

Input x

x= x + 1

output x

Compiler

Machine code (program)

01010010110

CPU

(executes)

Input�data

Output�data

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Translator

Source code (program)

Input x

x= x + 1

output x

Interpreter

CPU

(executes translator)

Input�data

Output�data

Interpreter reads one line at a time and executes the operation.

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Computers are machines

Execute a set of instructions that describe a process
Types:

Fixed Program - always same program

Calculator
Microwave oven
?

Stored Program computer - machine stores programs and executes them

Laptop
Desktop

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Stored Program Computer

sequence of instructions stored inside computer

built from predefined set of primitive instructions�1) arithmetic and logic�2) simple tests�3) moving data

special program (interpreter) executes each instruction in order

use tests to change flow of control through sequence
stop when done�

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WHERE THINGS GO WRONG-3 Types of Errors: T-P-S

Syntax errors

Violation of grammar/structural rules
Common and easily caught (by compiler/interpreter)

Run-time errors

Show up while running program
Program crashes/halts

Logic/Semantic Errors

Program runs and gives an answer but different than expected
Program behaves differently from what the programmer intended�

Car Analogy to explain types of errors

Car won’t start
Car runs but crashes
Car runs and arrives at a place but different from the intended destination

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Foundations of Programming

Alan Turing (1912-1954) showed anything can be computed with only 6 primitive operations: Turing Machine, basic model of computation.

Modern programming languages have many convenient primitives built on basic primitives to make programming easier.

It turns out that anything that you can compute in one language you can compute in any other language.

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Aspects of Programming Languages

Language primitives

English: words�
Programming - numbers, strings, operators (tokens), keywords

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Goal

Learn the syntax and semantics of a PL
Use those elements to translate “recipes” for solving a problem into a form that the computer can use to do the work for us
Learn computational modes of thought to enable us to leverage a suite of methods to solve complex problems
Analogy with human language: Knowing the grammar and syntax for a language is necessary but not sufficient to write meaningful/useful/beautiful essays, articles, books, poems

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Python Programs

a program is a sequence of instructions: definitions and commands

definitions evaluated
commands executed by Python interpreter in a shell

commands (statements) instruct interpreter to do something

can be typed directly in a shell or stored in a file that is read into the shell and evaluated�

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Python Objects

programs manipulate data objects (values)
objects have a type that defines the kinds of things programs can do to them
objects are

scalar (cannot be subdivided, also called literals)
non-scalar (have internal structure that can be accessed)

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Scalar Objects (Literals)

int – represent integers, ex. 5
float – represent real numbers, ex. 3.27
bool – represent Boolean values True and False
NoneType – special and has one value, None
can use type() to see the type of an object� In [1]: type(5)� Out[1]: int�� In [2]: type(3.0)� Out[2]: float

When you type this

The type is shown

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Type Conversions (Casting)

can convert object of one type to another
float(3) converts integer 3 to float 3.0
int(3.9) truncates float 3.9 to integer 3

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Print to console

To show output from code to a user, use print command�

In [11]: 3+2�Out[11]: 5�

In [12]: print(3+2)�5

No “out” because nothing in returned,

Just something printing

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Expressions

combine objects and operators to form expressions
an expression has a value, which has a type
syntax for a simple expression

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Arithmetic OPERATORS on ints and floats

i+j ➞ the sum
i-j ➞ the difference
i*j ➞ the product
i/j ➞ division
i//j ➞ int division
i%j ➞ the remainder when i is divided by j
i**j ➞ i to the power of j

- if both are ints, result is int

- if either or both are floats, result is float

Result is float

result is int, quotient without remainder�

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Simple Operations

parentheses used to tell Python to do these operations first

3*5+1 evaluates to 16
3*(5+1) evaluates to 18�

operator precedence without parentheses

**
*
/
+ and – executed left to right, as appear in expression>

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Variables and Assignments

equal sign is an assignment of a value to a variable name�
pi = 3.14159
pi_approx = 22/7
value stored in computer memory
an assignment binds name to value
retrieve the value by invoking the variable name

variable

value

If we use 22//7, value of expression is 3

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