cs
61a


course
summary


you
aren't
expected
to
understand
this
yet
but
keep
it
for
reference
during
the
semester
and
see
if
it
starts
to
make
sense

------------------------------

abstraction




voluntary
submission
to
a
discipline




in
order
to
gain
expressive
power

------------------------------

1

functional
programming

focus
repeatable
input-output
behavior


composition
of
functions
to
layer
complexity

hidden
side
effect
mechanisms
assignment


internal
control
structure
of
procedures

2

data
abstraction

focus
semantic
view
of
data
aggregates

hidden
actual
representation
in
memory

3

object
oriented
programming

focus
time-varying
local
state


metaphor
of
many
autonomous
actors

hidden
scheduling
of
interactions
within
the
one
computer


procedural
methods
within
an
object

4

concurrency

focus

process
separated
from
serial
execution
limitations


coordination

hidden
mechanisms
for
serialization

new
in
2nd
ed
sicp

5

streams

focus
metaphor
of
parallel
operations
on
data
aggregates


signal
processing
model
of
computation

hidden
actual
sequence
of
events
in
the
computation

6

programming
languages

focus
provide
a
metaphor
for
computation


embody
common
elements
of
large
groups
of
problems

hidden
technology-specific
implementation
medium


storage
allocation
etc

7

logic
programming

focus
declarative
representation
of
knowledge


inference
rules

hidden
inference
algorithm


note
each
of
these
abstractions
can
be
approached
from
above
focusing
on
the
view
of
computing
that
the
abstraction
provides
or
from
below
focusing
on
the
techniques
by
which
the
abstraction
is
implemented

in
the
metacircular
evaluator
we
emphasize
the
view
from
below
since
we've
been
working
all
along
with
the
view
from
above

in
the
query
evaluator
we
emphasize
the
view
from
above
barely
mentioning
the
implementation
techniques

in
our
discussion
of
object
programming
both
views
are
used