computing: behind the scenes

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computing behind the scenes

• part III systems software

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data, software, hardware

• data symbols that represent information
• software instructions for manipulating data
• hardware physical devices/tools that perform the
  instructions in the software and store the data

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where is the data? software? hardware?

• cooking from a recipe
• reading a book
• playing a musical instrument
• ...

4
recall hardware

• (configuration in typical personal computer)

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RAM (random access memory)
Peripherals (hard drive, monitor, keyboard,
mouse,...)
instruction memory
Processor
...
up- date
program counter
data memory
register
register
ALU
register
...
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Peripherals
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hardware many innovations

• multiprocessor machines
• memory hierarchies (cache)
• ...

8
designing hardware

• computer architects design hardware
• design process involves creativity, experience,
  insight
• use available materials
• manage with limited space
• optimize resources such as communication

9
remember your nanoseconds!

• The "nanoseconds" that Grace Hopper handed
  out were lengths of wire, cut to not quite 12
  inches in length, equal to the distance traveled
  by an electron along the wire in the space of a
  nanosecond--one billionth of a second. In
  teaching efficient programming methods, Admiral
  Hopper wanted to make sure her students would not
  waste nanoseconds.

From Tribute to Grace Murray Hopper by Merry
Maisal http//www.sdsc.edu/Hopper/GHC_INFO/hopper.
html
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software the context

• computer users typically want to run many, many
  applications, often at the same time
• a computer may support many users
• applications may be distributed over more than
  one computer

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imagine scaling up the context in examples

• cooking from a recipe gt running a restaurant
• reading a book gt managing a library
• playing a musical instrument gt conducting an
  orchestra
• ...

12
software in the restaurant

• recipes, protocols for taking orders, seating
  customers, communicating between staff, and on
  and on and on

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software in the library

• catalogue system, methods for finding books and
  other materials, system for checking out
  materials, handling lost, late materials, and on
  and on and on...

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system versus application software

• application software refers to word, netscape,
  photoshop, email, genome sequencing, and so on
• systems software refers to the support software
  in the background
• note boundary between application and systems
  software is not well defined

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what system software services can you think of?
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typical operating system services

• organizing the file system
• downloading software
• scheduling programs on the processor
• interfacing with the internet
• managing communication with peripherals
• managing memory
• providing security
• other (GUI, windows, ...)

17
unix operating system

• developed in early 70s
• command line interface
• innovations include
• hierarchical file system
• ability to run several programs simultaneously

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windows operating system

• inspired by early GUIs developed at Xerox PARC
  (Palo Alto Research Center) in early 80s
• earliest version released in 1985

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designing operating systems

• how to gracefully handle many concurrent events?
• how to present a useful, consistent interface to
  the programmer and computer user?

20
more system software translating between
programming languages

• compilers help to translate programs written in a
  high level programming language, such as java,
  into the low level machine language understood by
  a computer processor

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a compiler is a program whose input and output
data are programs!
compiler
high level program
low level program
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summary

• operating system software that coordinates and
  manages resources on the computer
• compiler software that translates programs
  written in a high level language into a low-level
  language