Computers and Computing. COS 111 Computers and Computing.

Computers and Computing

COS 111 Computers and Computing

When did you first start to use a computer, and what for?

What do you use a computer for today?

What are some of most important uses of computers, other than your own?

What abilities do you need in a computer?

What are the major changes you’ve observed in the use of computers?

What are the major changes you’ve observed in computers themselves?

What are the major changes you expect to see over the next few years?

What are the major changes you would most like to see over the next few years?

When Was the Computer Invented?

When Was the Transistor Invented?

When was the Microprocessor Invented?

When Was the Internet Invented?

When Was the World Wide Web Invented?

What is the Difference between the Internet and the WWW?

A Brief History of Computer Time

• Harvard MK-I and Colossus: 1943– Colossus designed to crack German coding system– Vacuum valves as “transistors” and punched cards for storage

• ENIAC: completed 1946 (first generation)– Weighed 30 tonnes; contained 18,000 electronic valves; consumed 25KW of power; could

do 100,000 calcs/sec

• Transistor: 1947 (second generation)

• Integrated circuit (third generation: minicomputers)

– 1958; first commercial implementation 1963

• Microprocessor (CPU on a chip)

– First commercial in 1971 (Intel 4004)

– 60,000 instructions/sec (supercomputers like Cray 1 were 150M)

• Personal Computer: MITS Altair 8800 in 1974

– Followed by Apple 1 and II, Commodore, and IBM PC (1981)

A Brief History of Internet Time

• ARPANET: DARPA research project started 1969– First RFC: April 7th, 1969

• Opened to non-military use in 1970s– Big universities

• Opened to international connections 1972– Still no email, web etc; just networking and research

• Domain names etc in mid 80s; standardized email

• World Wide Web 1989– For physicists to share information; usage begins 1991

• Web takes off: Mosaic (1993); Netscape (1994)

Who Invented the Internet?

• Al Gore

• Kleinrock (packet switching theory: 1961)• Roberts (plan for ARPANET: 1969)• TCP Team: 1974• First virus team: 1980

What is the Role of Computers in Cosmology and Astrophysics?

What is the Role of Computers in the Human Genome Project?

Why are You in this Class, and What do You Hope to Get out of it?

The Following is Not a Test …

Some Questions

• What happens between the time I send an email and you receive it?

• What happens between the time you submit a URL to a browser and you see the page returned?

• What happens between the time you submit a query to a search engine and you get results back?

• Where do the data that a search engine returns come from?

Some Questions

• How long does it take for a request to go from NY to San Francisco and back on the Internet?

• How long does it take for light to go from NY to SF and back?

• What is “market cap?”

Some Questions

• What is TCP/IP?• What is IP?• What is TCP?• What is HTTP?• What is HTML?• What is SMTP?• What is MP3?• What is JPEG?• What is the size of a 3 minute audio file?• What is the size of a 3 minute video file?

Some Questions

• What is Java?

• What is C?

• What is a compiler?

• What is Windows?

• What is an operating system?

• What is Linux?

• What is Unix?

• What is the difference between RAM and a hard drive?

• What is a cache?

Some Questions

• What is SETI@Home?• What is Napster?• What is Gnutella?• How are Napster and Gnutella similar and different?• What is the legal implication of the difference

between Napster and Gnutella?

Some Questions

• What does “security” mean in the context of computers?

• What are some key aspects of computer security?• What is DRM?

Should You be Here?

• COS 111 is intended for students from the humanities and social sciences who want a one-course introduction to computers and computer science. Emphasis is on understanding how computers really work, starting with a single switch, and showing step by step how to use just that one kind of part to build the most interesting human-made machine. Also addressed are essential limitations of the computer, such as undecidability, as well as future prospects for artificial intelligence and on-line access to the world's knowledge. The laboratory is complementary to the classroom work and explores a broad spectrum of modern applications.

So is he only going to ask questions, or is he going to teach?

?

What Does a Computer Do?

Whatever I tell it to do

• I say: Add 2 and 3 and show me the result– Computer says: 5

• I say: Multiply that result by 7 and show me the result– Computer says: 35

• I say: Show me the home page of the Princeton CS department– Computer says:

What’s Going On?

The Ghost in the Machine• Read an input and memorize it• Read another input and memorize it• Add the inputs and display result• Read input and memorize it• Multiply input with previous result and display the result

• Hardware does the work• Programmer writes a program for the machine• Program tells hardware what to do at each step

What Programs Look Like

read (a)

read (b)

c = a + b

read (d)

e = d * c

print (e)

; Read first input and store it in variable a

; Read second input and store it in variable b

; Add the values of a and b and store the result in variable c

; Read third input and store it in variable d

; Multiply the values of c and d and store the result in variable e

; Display the value of variable e

• The computer takes each of these instructions and executes it

The Computer’s Job

• Computing outputs from inputs• Memory• Accepting inputs and producing outputs• Sequencing steps• Maintaining state• Networking• Representing and translating information• Compiling and managing programs

Rest of the Course

• Hardware: Building a computer (7 classes, 3 problem sets)

• Operating Systems and Networking (3 classes, 2 problem sets, 3 labs)

• Midterm review and Midterm (2 classes)

• Programming and Algorithms (4 classes, 2 problem sets, 2 labs)

• Sound and Graphics (2 classes)

• Distributed Applications (1 class)

• Limitations of Computing (1 class)

• Societal Issues and Applications (3 lectures, 1 problem set, 1 lab)

• Review (1 class)

Practical Details

• Lectures Monday and Wednesday 1:30-2:50 p.m.– Lecture slides will be online

– Class participation expected

• Labs– Start week of 2/10, due by Friday at 5PM

– Can do in lab sessions or elsewhere

– To be scheduled

• Problem Sets– Handed out Monday, due Wednesday (9 days later)

Practical Details

• Paperless course– All assignments, lecture notes on web

• Go to http://www.cs.princeton.edu • Click on fall courses• Click on COS 111

• Problem sets– Lowest score dropped– Must do 7 of 9 to pass the course

• Labs– Must complete all labs to pass the course

• Midterm and Final