CS24: Introduction to Computer Systems

CALTECH CS24 Spring 2004 -- DeHon

CS24:Introduction to

Computer Systems

Day 1: March 29, 2004Introduction and Overview


Today

• What • Who• Why• What Detail (Overview)• How (Course Details)


What

• How the computer works below the programming language– (mostly above the physics)

• How processor is organized– How your computation is actually

performed• Why is there an Operating System

– And what does it do for you?


What

• What lies between the – Programming

Language– Physics

• Abstraction Stack


What • New class

– First time being taught here• Only course in CS undergraduate core that

actually deals with computers as physical machines

• Dynamics / typical case • How we manage computer systems

– Coordinate shared resources– Not just one program

• How do we deal with technology– Technology change


Who?

• Two Instructors– Jason Hickey

• represent high-level view• What does the Programmer want?

– André DeHon• Represent the low-level view• What does the hardware want?

– How does it perform well?


Who?

• TAs:– Michael Wrighton– Cristian Tapus


Why? (low road)

• As programmers: want to understand your tool.– How does it work?– When does it break?– What are those constants we kept ignoring

in CS20, CS38?– How do you get the most out of it?

• Why is this a challenge?


Why?

• As innovators: want to understand the prior art– How does it work?– What’s wrong with it?– How can we make it better?


Why? (high road)

• What problems does it solve?– What are the big ideas that makes this

work?• Is the Instruction Set Architecture (ISA)

abstraction necessary?• Isolation?• Virtualization?• …


Why? (Future)

• This will all break down in the next 10-20 years.– Low-end: Approaching Atomic scale

• Time to pay attention to low-level physics – Sequential processor at end of scaleable life– High-end: Scale of modern systems/software

already stressing (breaking?) model• How do we enable bigger systems?• In critical roles?• Reduce human time?


Why? (Future)• This will all break down in the next 10-20

years.• We’re going to have to rebuild it.

– What were the good/high-level ideas we need to keep? Can and should be transferred?

• You:– May need to help lead the transition– At least need to understand the big ideas to

survive the transition


Why?• We are not learning this to pay homage to

– Bill Gates– Dennis Richie, Ken Thompson– Linus Torvalds– Fred Brooks, Gene Amdahl– John Hennessey, Dave Patterson– Bob Colwell

• Learning this so we can move forward while not repeating the mistakes of the past– Keep the good ideas– Discard the bad ones– Solve problems they didn’t need to…


Back to What


Physics

• Ultimately, we can build machines which compute because the physical world computes F=0,F=ma, F=-kx, … I=0,V=IR, V=(I T)/C,

Id=Is(e[qv/kt]-1)


Devices

• From these phenomena we can build useful devices– Store charge store value– Switch current based on value


Gates

• From these devices we can build gates


Boolean Logic

• From gates we can build any particular boolean function– E.g. o=(a+/b)(b+c)+/b*/c

Day 2


Universal Turing Machine

• From CS21 (CS20), you know we can, in theory, – build a machine which will emulate any

other machines– A Universal Machine…


Programmable Logic

• Likewise, we can build collections of gates which will perform any function


Programmable Machine

• …and ultimately, a machine which can perform (almost) any computable function

Week 2


How Organize Programmable Machine?

• Theory tells us that we can build such a machine?

• Engineering asks how we should build such a machine


What’s in here?


Raw Machine

• Even this is pretty raw– add, or, xor, ld, st, br

• How do we make it usable?• Invent conventions:

– Using memory– Representing data– Making procedure calls


Runtime Systems

• Over time, we build up a collection of software necessary to run the machine– Load program– Allocate/deallocate memory– Perform I/O– Handle asynchronous events– …


It might be nice if…

• Could run more than one program• All the programs didn’t need to know about

each other• Could run more than one program at a time

– Didn’t require a physical processor for each program want to run

• Could use more memory than you have physical RAM

• Could communicate with other programs


It might be nice if…

• One program crashing didn’t crash the machine

• Could monitor a running (crashed) program

• Could share the machine amongst people (programs) that don’t necessarily know about or trust each other…


Operating System

• …we need some way to virtualize and manage our physical resources

• This is what an Operating System provides

• Most of our programs run in the context of an operating system and an instruction set processor– API: Application Programming Interface


What

• What lies between the – Programming

Language– Physics

• Abstraction Stack


How


Course Components

• Text (CS:APP)• Lectures• Recitations

– Fri. 4pm here– Also Fri. 2pm (TBD)

• Homework– 9 weekly labs

• Midterm, final

• Grade: 70% for best 8 of

9 labs 10% midterm 20% final


Resources

• Course Web Page<http://www.cs.caltech.edu/courses/cs24/>

• Administrative handout – Give you all of these details

• Mailing Lists• Forum• Computer Accounts


Pragmatics

• Programming in C and Assembly– First recitation on C– Text has asides for “new” C programmers– …will learn assembly bottom up– …will help C, since C is so close to

assembly…• Online submission systems


Feedback Sheets

• Please fill one out each class– anonymous

• New course– Need to understand what works– So can improve for future lectures– So can improve for future years


You Action Items

• Get book• Read chapter 1• Find web page• Read administrative handout

– Signup for mailing list, find forum• Get computer account

– If don’t already have one• Read Assignment 1

– Pickup support code


Big Ideas

• Valuable not to program physics directly – (most of the time…)

• Abstraction hierarchy– From programming language to physics

• Valuable to abstract and share resources• Need to Understand Hierarchy

– to make the most of machines– to improve/re-invent


Questions

CS24: Introduction to Computer Systems

Documents

Transcript of CS24: Introduction to Computer Systems