CS 101

Introduction to Computers

reading: Syllabus

Plan for Today

  • Course Overview
  • Computer Code
  • Computer Hardware

Course Goals

  • Demystifying Technology
  • Technical Literacy
  • Communication with Software Engineers

Course Overview

  • Computer Hardware (~3 lectures)
  • Introduction to Code (~7 lectures)
  • Artificial Intelligence (~1 lecture)
  • Wifi and the Internet (~3 lectures)
  • Security (~3 lectures)
  • How the Web Makes Money (~1 lecture)

Course Policies: Grade Breakdown


Course Policies: HW

  • Weekly homework, out Tuesday, due following Monday
  • Combination of written questions and code exercises
  • Two free 24-hour late days (pre-approved extensions)
    • Each late day covers 1 second to 24 hours late
  • Submit on Canvas
  • Short response paper on Artificial Intelligence
    • released week 6, due Thursday, May 31
  • Work should be individual (Stanford Honor Code)

Course Policies: Exams


  • Thursday, May 10 in class
  • Covers first five weeks of lecture
  • Closed note, closed book, reference sheet will be provided


  • Friday, June 8, 8:30-11:30AM
  • Closed note, closed book, reference sheet will be provided
No alternate exams will be offered except for OAE and athletic conflicts.

Introduction to Code

Strengths of Computers

  • Very fast (billions of operations per second)
  • Very accurate

Weaknesses of Computers

  • Literal
  • Only simple operations
    • Addition
    • Comparison
    • Equality
  • No insight

Introduction to Code:
How Computers Work

  • Code is a series of instructions
  • Each instruction is an operation
  • Computer follows each instruction, one after another

Introduction to Code:
The Programmer

  • Computers are hugely useful
    • Messaging
    • Image editing
  • Programmers convert human ingenuity into computer code
  • Develop algorithms (which we'll see later in the course!)

Introduction to Code:
Tips and Previews

  • Code is like Legos - small bricks to big structures
  • Patience :)
  • Computers do exactly what you tell them
    (no interpretive power)
  • We'll be doing green screen soon!

Introduction to Code:
First Code Operation

  • Using Javascript (plus some extensions for 101)
  • Each line of code is small
  • First line: print!



Introduction to Code: Bugs

Story: named after a moth

Two types: syntax and logic errors


Introduction to Code: ASCII Art

We can use print statements to make art


Introduction to Hardware:
Hardware vs. Software

  • Code is the software
  • Physical part of the computer is the hardware
  • Like piano (hardware) vs. music (software)
  • Hardware interprets the code

Introduction to Hardware:
The Transistor

Source: https://pixabay.com/en/transistor-electronics-science-24529/
  • Building block of electronics
  • No moving parts ("solid state")
  • Essentially acts as an on/off switch controlled with electric current

Introduction to Hardware:
Silicon Chips

Source: https://en.wikipedia.org/wiki/Integrated_circuit#/media/File:EPROM_Microchip_SuperMacro.jpg>
  • Transistors grouped together on silicon chips
  • Very small (size of a fingernail)
  • Each chip has billions of transistors
  • Metal legs connect the chip to the outside.

Moore's Law

Transistors get twice as small every two years

Source: https://upload.wikimedia.org/wikipedia/commons/0/00/Transistor_Count_and_Moore%27s_Law_-_2011.svg>
  • Observation not a scientific law
  • Implications:
    • Chips of the same size have twice the capacity every two years
    • Keeping capacity constant, chips get smaller and cheaper every 2 years
  • Not indefinite
  • Allows chips in anything with a control system

Introduction to Hardware:
Parts of a Computer

Introduction to Hardware: CPU

CPU: Central Processing Unit

  • The "brain" of the computer
  • Follows the code's "instructions"
  • Performs computations (changes data)
  • Measured in "hertz": operations per second
  • CPU Cores: each core is like a mini CPU
    • 4 cores is NOT 4x faster than 1 core
  • GPU: Graphics Processing Unit
    • CPU that specializes in image processing (video games use GPU)

Introduction to Hardware: RAM

RAM is temporary storage

  • Random Access Memory
  • Used as a workspace (computer's whiteboard)
  • Stores code and data (temporarily)
  • Calculations are performed in RAM
  • Not "persistent"
    • Unplug a computer, and an unsaved document disappears
    • State disappears when power is turned off
  • VERY fast
  • Examples?

Introduction to Hardware: Persistent Storage

  • Long term storage
  • Data is preserved even without power
  • Organized in a file system
    • File is a name to a piece of memory

Hard Drive Flash
Moving parts No moving parts (solid state)
Cheaper Faster, requires less power
Generally more capacity Works quickly with files of all kinds


  • Connects all the parts of a computer
  • Lets various components communicate
  • CPU metal package is in the center


Each gold pad is connected to a part of the silicon chip (connection to outside world)


Comprised of multiple chips, and plugs into the motherboard.

Hard Drive

  • 3.5"
  • Connects to motherboard via cable
  • Spinning hard drive inside

Flash Drive