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CALTECH CS24 Spring DeHon 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?
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CALTECH CS24 Spring 2004 -- DeHon
CS24:Introduction to
Computer Systems
Day 1: March 29, 2004Introduction and Overview
CALTECH CS24 Spring 2004 -- DeHon
Today
• What • Who• Why• What Detail (Overview)• How (Course Details)
CALTECH CS24 Spring 2004 -- DeHon
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?
CALTECH CS24 Spring 2004 -- DeHon
What
• What lies between the – Programming
Language– Physics
• Abstraction Stack
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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?
CALTECH CS24 Spring 2004 -- DeHon
Who?
• TAs:– Michael Wrighton– Cristian Tapus
CALTECH CS24 Spring 2004 -- DeHon
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?
CALTECH CS24 Spring 2004 -- DeHon
Why?
• As innovators: want to understand the prior art– How does it work?– What’s wrong with it?– How can we make it better?
CALTECH CS24 Spring 2004 -- DeHon
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?• …
CALTECH CS24 Spring 2004 -- DeHon
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?
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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…
CALTECH CS24 Spring 2004 -- DeHon
Back to What
CALTECH CS24 Spring 2004 -- DeHon
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)
CALTECH CS24 Spring 2004 -- DeHon
Devices
• From these phenomena we can build useful devices– Store charge store value– Switch current based on value
CALTECH CS24 Spring 2004 -- DeHon
Gates
• From these devices we can build gates
CALTECH CS24 Spring 2004 -- DeHon
Boolean Logic
• From gates we can build any particular boolean function– E.g. o=(a+/b)(b+c)+/b*/c
Day 2
CALTECH CS24 Spring 2004 -- DeHon
Universal Turing Machine
• From CS21 (CS20), you know we can, in theory, – build a machine which will emulate any
other machines– A Universal Machine…
CALTECH CS24 Spring 2004 -- DeHon
Programmable Logic
• Likewise, we can build collections of gates which will perform any function
CALTECH CS24 Spring 2004 -- DeHon
Programmable Machine
• …and ultimately, a machine which can perform (almost) any computable function
Week 2
CALTECH CS24 Spring 2004 -- DeHon
How Organize Programmable Machine?
• Theory tells us that we can build such a machine?
• Engineering asks how we should build such a machine
CALTECH CS24 Spring 2004 -- DeHon
What’s in here?
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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– …
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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…
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
What
• What lies between the – Programming
Language– Physics
• Abstraction Stack
CALTECH CS24 Spring 2004 -- DeHon
How
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
Resources
• Course Web Page<http://www.cs.caltech.edu/courses/cs24/>
• Administrative handout – Give you all of these details
• Mailing Lists• Forum• Computer Accounts
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
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
CALTECH CS24 Spring 2004 -- DeHon
Questions