1. CS/COE 0447 Jarrett Billingsley
Welcome!
CS/COE 0447
Jarrett Billingsley

2. Administrivia
CS447

3. jarrett@cs.pitt.edu pitt.edu/~jfb42 hi you can just call me Jarrett

4. Textbook (optional)
Computer Organization & Design (Patterson & Hennessy)
don't buy it if you don't want to
5th edition is stupid ("PostPC" crap)
- I don't really use it at all
- has some good stuff, has some overly-detailed stuff, has some bad stuff
CS447

5. Grading there is no such thing as attendance labs: 10%
graded on effort/completion
projects: 50%
two in MIPS assembly language, one in Logisim
lowest grade worth 10%; other two worth 20%
exams: 40%
lowest grade worth 16%, other 24%
CS447

6. Expectations religious absences: contact me ASAP
students with disabilities: contact the DRS ASAP
cheating:
first time, fail the assignment
second time, fail the course
you can work with one partner on projects
inform me ahead of time, and do not share code!
jokes/comments about sex, gender, race, ethnicity, religion, etc. are inappropriate for class, s, office hours, chats etc.
have you considered being nice?
it's pretty neat :O
CS447

7. Teaching philosophy I wanna help you understand!!!!!!
NO QUESTIONS ARE DUMB!!!!!
NEVER BE AFRAID TO ASK THEM!!!!
DON’T STRUGGLE IN SILENCE ON YOUR PROJECTS/LABS!!!!!!!
what is a university setting good for today?
focus, practice, and access to people who know stuff
I trust you!
I try to be accommodating re: extensions
I don’t think most cheaters are being lazy
but you’re an adult, and are responsible for your actions.
CS447

8. I can tell when you cheat :^)
If you're confused, don't cheat, ask me for help
don't wait until you get an F on the first exam
hot tips for not cheating:
don't
cmon, don't
don't post your code on github
if your enrollment is contingent upon your GPA, DON'T CHEAT
duh?????????
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9. Introduction and Context
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10. Goals of this course
”447 tries to convince you that computers exist.” – Dr. Misurda
447 and 449 teach some similar topics from different angles:
data representation
memory organization
how programs really run
the call stack and calling conventions
this course also establishes important fundamental skills:
numerical bases and representation
logical operations
understanding logic diagrams
CS447

11. More goals Java has poisoned your mind
ok it's fine for algorithms but it's too high level to explain computer
learning assembly is like a car mechanic learning how an engine runs
- a normal person doesn't need to know this stuff
- but you're not normal, are you?
CS447

12. Where does this material fit in with CS and EE?
the “hardware-software interface”
where CS and EE overlap
each layer affects/is affected by layers above and below
ISA: Instruction Set Architecture
Programmer's interface to the computer hardware
logic design
how we make rocks Do Stuff
doing Lots of Stuff (aka a CPU)
Computational Theory
Algorithm Design
Applications
Operating Systems
ISA
Logic Design
Electrical Design
Physics
more abstract more concrete
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13. Classes of computers: Embedded (Microcontrollers)
very cute
8/16-bit architectures are still common
as little as 32 BYTES of memory!
almost always run one, built-in program
focus on ultra-low power, cost, and size
becoming more common every day
“Internet of Things” (IoT)
now your fridge can crash, your TV can crash, your dishwasher can crash, and your lightbulbs can be a botnet
what a stupid future
CS447

14. Classes of computers: Consumer-grade (PC/Mobile)
1-8 cores, 32/64-bit architectures, MB-GB of memory, GB-TB of persistent storage
multitasking operating systems
similar capabilities, different design goals
focus is real-time user interaction: productivity, media, browsing, games
despite what the book says, I really don’t think we’re in a “Post-PC” era
who’s gonna do all their work on a touchscreen using gimped sandboxed apps
- NOT MEEEEEEEEEE
CS447

15. Classes of computers: Servers and Mainframes
from high end desktops to much more powerful machines or groups of machines
dozens of cores, 32GB+ of RAM, massive storage systems, very high-speed networking
focus on real-time data delivery - either from storage or after processing
redundancy and hot-swappability
goal is 100% uptime
power and cooling become huge concerns
CS447

16. Classes of computers: Supercomputers
cluster of hundreds to thousands of CPUs
focus on crunching ENORMOUS datasets non-interactively
science, research, design, and simulation
and now, stock trading and "cryptocurrencies"…
- bitcoin is expected to consume more power than all of ireland by the end of the year
- what a fucking waste of resources
- cryptocurrencies are a scam btw
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17. General computer organization
Control
Registers
Datapath
Processor
Memory
Persistent Storage
Other Peripherals
Other Computers
Input/Output Devices
Network
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18. Machine and Assembly Languages
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19. compilers and VMs turn HLLs into machine language.
Lost in translation
"high-level" programming languages like Java exist for us
int doSomething() { this.x = 10;
return blarf(); }
??????
computers can only follow instructions written in machine language.
- computers don't have any idea what to do with Java, C, C++, Python etc.
- HLL = high-level language
compilers and VMs turn HLLs into machine language.
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20. What is machine language?
a computer has a fixed set of things it can do.
machine language is a numerical encoding of those operations.
you could write "programs" by listing the columns/rows of buttons to press in order:
(2,2)(4,4)(3,1)(3,4) =
CE * MS 6
- big difference between (non-programmable) calculators and computers:
- calculators *can't run the instructions themselves*
- you are acting as the "control unit"
- a list of instructions for one might be garbage to the other!
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21. What is assembly
assembly is a human-readable representation of machine code
so it gives us direct control over the hardware…
…but at the expense of so many useful things
the CPU is no more "intelligent" than a hand which can listen to instructions and push buttons on a 4-function calculator.
- no types and type-checking
- no control structures (ifs, loops, functions)
- no automatic memory management
- no imports, namespacing, classes, objects…
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22. Is assembly language useful today?
“assembly is fast, so we should use it for everything!” no,
it's not great for writing large programs
it can be dangerous, like with the Therac-25
still useful for debugging (like in 449!)
if you write a compiler, you have to generate it
since that's what a compiler does
good for extremely performance critical low-level code, like:
device drivers
some parts of operating systems
High Performance Computing (simulations etc.)
increasingly fewer parts of video games
and…
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23. Embedded systems
you would be amazed how many CPUs are in any given device
many of these are programmed largely or entirely in assembly
many people use C but they're wrong,
- ofc as MCUs (microcontrollers) become more complex, they become programmable with HLLs
- now we have MCUs that are more powerful than entire home PCs were in the 80s
- but like
- that just feels wrong, doesn't it?
CS447