Alan Kay - Programming Languages & Programming

let me give you the professor LK professor

L K is best known for his pioneering work an

object-oriented programming language and we know

a graphical user interface design and for coining the

phrase the best way to predict the future is to invent

it into in 2003

Professor Alan can receive receive

a ACM Turing Award they consider to

be the Nobel Prize of computing from work on object-oriented

programming let us welcome Professor Alan Kay

okay

the ground rules here are

ask questions whenever

you have one because these classes

go quickly just think of all

the money you're paying for hardly getting anything in

a in an hour so

programming languages in programming

one of the problems of talking about this in general especially

in one class is that there have been

several thousand programming languages

designed and implemented over the years

at any given time since the

early 60s there have been somewhere

between 150 to 200 languages in

standard use and these

languages are rather different from each

other in certain ways and rather

similar to each other in other ways and so

it's very hard to come up with interesting generalizations

and

what we're really talking about here is programming

and programming is

the simplest thing to describe it's we

do something in the computer does something and

if it does what we wanted it to do both

of us are successful programming

languages are usually the vehicle for

this and you can think

of user interfaces as

kind of an impoverished kind

of programming language they used to be

richer and that

the kinds of things that you did

in the user interface were part and parcel of the

you could do and I'm going to show you a few of those things

today so I thought what I do is

first to just look

couple of ideas in programming and programming languages

and be able to do it

so I don't have to explain some

programming language you've never seen before I'm going to take a

programming language that is currently

in use by about three million children called eToys

it's the parent of

another widely used programming

language for children called scratch and

some

of the same people worked on both of those and so I'll first

take a look at what that experience is like and

so the basic idea in

this style of doing

programming it's now has a name

called live coding

but back live coding goes all the way

back to the early 60s it

just never was in the style of the punch

card UNIX approach

black screen by terminal

way of doing things so the idea is

that you

just make things in

a variety of ways and the computer responds to them there's no

no visible compiling or we're

editing so pick up some paint

one of the things that kids like is

to do

things that adults do so

you can ask them

why don't you draw a car from

the top view put

on some headlights

and

we were at Disney for a while and so

the thing we learned at Disney is you must always put on some specular

reflections

like that and this this

gives you a graphical object and it does the kind

of things you'd expect with a graphical object

I can give it a name here I'll call it car and

what's interesting about this object is it has another

view this is the symbolic view of

this object and so

here's a property of

it called the heading of it says the heading is zero

and if I rotate the

car you can see it's showing me the degrees from

north minus and plus and

this is interfaces reflexive so if I

go in here and right

so everything is by connected

here and also here here's

a behavior of the car turn

by five if I click it it turns

the car if I drag it out it makes me a little script

if I get the script is

now just infinitely looping and

if I

pull out another thing

each time I'm doing this is the

there's a compilation going on but

it's sub-second so it's actually

compiling a code underneath it and

I can actually even drive

my little car the

zero makes it go straight

but in fact it's hard to drive the

car this way and

it's a little bit like kissing your sisters we really want

steering

wheel so

we'll just make a steering wheel

and

we'll call it wheel

and again

we look inside here we see oh this is just the same kind

of audit it's just got a different costume on

it and again it has a

heading and I

get the same behavior from

it but notice that we

got the car to turn by changing

this number here and that's

kind of an invitation of picking up this value and dropping it into

the script and

now we get to do

so you're just starting out here

but let me tell you if you program

language here at UCLA that doesn't allow you to do this

little demo right off the bat something

is wrong because we're looking at something that goes

back 40 years this

is just because you don't know what you're getting into

here I'm just trying to show you that there

doesn't have to be a compile phase it doesn't

have to be edits of files it can all be done

lickety-split okay

so I've got a little car there and

the other thing I can do is

make

lots of them so I'm

going to play a game got

a red car and a blue car and I'm

going to make them small

can you see them blue

guy and the red guy there and the

two programs I'm going to run here this

little kids system has automatic multitasking as

many tasks as you want so

I'm going to say go forward

by one and turn randomly and this

one says I do

this guy and

if a blue guy sees

touches a red guy then make the blue

guy red so this is like an infection programming

and so if I say go at

the top here I'm plotting the infected

against the non infected you can see that the

big open space here that

the village is is kind of like a

kind of

like a long time constant the probability

that the two guys are going to hit is fairly low so I'm

going to get that behavior but

what about a

thousand

all of a sudden I

there's another thing if your programming language doesn't

allow you to make objects by the hundreds of thousands

and run them in parallel then you have to worry about

what kind of language you're programming it so the

kids with this little program that they wrote there's

no mystery here they wrote this program

so now they can explore

by saying well okay how about 200

and

again the sparseness acts like

a longer time constant between

infections but

eventually they all die

and

we get this longer thing so

the kids will say okay well how

now

they're starting to root for

the ones that are maybe no

so

this is kind of an experiment in system dynamics for 10

year olds and

it's something that many

parts the world don't actually understand on

any terms because this

first curve that I showed the one that went up rapidly

is like typhoid and

so

if this last one was a disease what would it be like what these

disease would it be blurt

it out

let's see it's a disease that's already

100 million people yeah come

on remember

you're in it you're right UCLA now

yeah so why does it kill

that many people when typhoid is

much much more virulent the answer is

unless you know that a

contagious incurable

deadly disease is always going to kill everybody

off no matter what the time constant

is you're not going to do anything when

it doesn't look like anything's going on remember people are also being

born so for a while

when AIDS is doing its work the population is

actually still rising and if you

don't happen to know this feature of

system dynamics you might just ignore

it or say it's just for minorities

or something like that then all of a sudden you've

got a majority of your population

infected ok so that's a little thought experiment

that children can do

it's important because

if you think about what is it that we need to know today

it's not so much knowing that two plus

two equals four or how to compute

a tip for a waiter

actually has to do with systems dynamics

because the world particularly biologically is

connected in more ways than it ever has been before

and also our

people

in Congress in Washington could do well to do a few

of these experiments because they'd actually have some

sense of how unstable

systems are and you shouldn't monkey

with them okay so back

back here we'll we'll turn this guy off

and I got to do two other quick

little experiments here

first one is to make a little robot car

now that we made one that can be driven

and for that I will need a track

so I'll get sort

of a brown track here

and

robots need

sensors so I need to put a sensor on this guy

so

I'll just draw one in here

like

this we'll

use this to track where are we where we actually

are and now we need

to make a program we can think out this program first

so one of things we do with children is get

o go around the wall of their classroom with their eyes closed

and the way

to do that they soon find out is you go

you hit the wall and then you turn away but

as soon as you lose the wall you have to go back into it

you keep on going if you don't

do that right away you may lose where the

wall actually is so right that

that little program

we want the

forward so I can get that we're

going to test whether we're touching the wall or not

here's a test that will

test

let's see how about

the

cars blue color

sees the walls brown color and

then we have to figure out which way to turn

here

okay I'm going to put in two turns by 5's

but let's think it through so

if we don't have the wall here which way do we want to turn

five or

minus five five okay

so

that's no and so four yes we'll

just take a guess and try minus five here

and we'll just start it going

okay

who can see what the flaw with this program

it is

somebody tell me

well

don't worry about efficiency

we aren't humans aren't efficient but we're smart

what's the

condition under which it can lose this

law it's

going to do with the Sun but if I made

a sharp turn right it's got a fixed radius

to get back so probably

lose the wall I might even want to stop

the car slowed it way way down to

give me a real chance of contacting the wall again

okay so

that's a little experiment

in making a feedback thing

now what I want to do is to

turn this thing into a wriggly

worm and to do that

I want

to make a script that is going to

change its shape so

here's my little thing it says car

look like something but I don't have anything

to make it look like so

I will

somebody talking

now

somebody isn't talking okay

so now I'm going

to draw a couple of

pictures for the wriggly worm part of this

I'll make a blue top and

maybe

a brown bottom here

and just to test this out

this

one is called sketch one so if I say do it

okay so that worked and

but I need another one in order

so I will

make a twin to

but with

the wriggle the other way

okay now I need

to move back and forth between each one of these and

which one of these I'm going to need something

that we might call a little data structure here

I'm going to put the worms in it

now I'm going to look again

see all of the objects here have

same kind of user interface I'm going to look down here

and see oh yeah here's here's

the cursor here's one that says the holders

player at the cursor so

I'm going to put that in there and

here's the cursor control so

I'm going to toss that in there and we're going

to say what I want to do is just increase the cursor

over and over again and so

now I'll start this script up

and you see what it's doing here okay

now we could have put that in as a feature for

the children

but then the children wouldn't understand

how to do animation so when you're trying to teach

something you don't want too many features you want them to actually

do the programming themselves

children have forgotten about these

other scripts that are there

so I could turn on this one and drive the

drive

the little worm around

or

what about this

okay so

okay so that's kind of simple programming

and the

other thing that you want to be able to get a

pretty early in your programming career is meta programming

and meta

programming in this case means I want to

I want to make another language other than eToys

and I'm going to do it

for the particle system kinds

of stuff so

here's the these are now

etoy objects in there

these are the scripts for the whole interpreter

I'm going to use the animate remember

the animation thing so if you know a little

bit about program counters the anime animation system

like running a program counter along when

you're doing animations what you're doing is saying display that

the guy that's that's there

in this case we're going to execute instructions

and so I'm actually

going to turn on the eval here

you can see it may be a little quivering a little

bit here dying for some input

and then the the instructions

are going to be implemented

using these scripts which have already written and

now I just have to build the instruction

and so this

one's is a test that says if

you can move this one says

then move okay so now it's executing that instruction

and this one says

if a

blue guy hits a red guy then

make them both red let's

see if we're lucky here yep

okay so

programming it and again when you're when

you're taking that java class and you

spent the first couple of weeks not really writing a

program yet think about what's like to write another

programming language in Java

should be really easy but

it isn't okay so

so one of the one of the theories

about designing programming languages is

because children

are part of our world and children grow up into

be being us we should

be able to have them be able to start

learning how to program this is we're

learning how to program and then if you do that well

the stuff that children

find easy and powerful or

actually clues for how to design a programming

language yourself okay

and so what we've been looking at here is here's

computer memory and

down a

fly speck in the machine is

actually some logic gates

on a chip one

corner of the chip and

around it is

nano code micro code

on the chip

itself and that

might be an 86 architecture kind

of chip but most of the chips are done the same way there's

some simple logic

like this is the arithmetic is our registers the

arithmetic unit and so forth

then it's made into a slightly more complicated

processor by putting a lowest level of programming

they're in pretty elemental terms

that's not always easy to write these

low level programs and

then nobody

wants to program in that so

in this case what we're looking at is a

virtual machine

coded ultimately in

these terms that

makes the computer look like a small talk machine

and at this level

there's an area on there that's manifested where

go and

then in that we

write a development system you still haven't seen

yes I'm

not going to but thank

you for the thought that's too complicated small

talk is a programming language that's all we need to know it

has a development system that's written in itself

and

the etoys system

that you saw which is putting up this

slide here is written in small talk

and then

I just made a little interpreter

in the eToys machine for doing

the rule-based particle system stuff

and this is a very typical way of

going about handling problems

it's not the only way

some people like the program down here

and write tons of programs to deal

with the very same problems another way of doing it is

fine languages v the problems gracefully

and then the amount of code you

have to write to get to the next level is not that large

and all of this is kind of an

example of

Turing's idea of being able

to simulate any kind of mechanism on a

relatively simple mechanism that has a few

pieces of logic and a fair amount of memory

okay so that's the kiddie

now let's take a look at the adult world where

we're going to go from programs that have

tens of lines in the kiddie

world but can still do interesting things to adult

programs which tend to have zillions of lines and

are surprisingly weak

and in order to come up with a metric for this

I'm going to use a metric of lines

of code it's not the

only metric you could use but a line of code is something

that a programmer has to write so it is one kind

of unit of work and it's also unit of space

so a 400-page

book has 20,000 lines

could be English

but it could be code could

be in machine code it could be in C

it could be in Java and a

foot of books is about 300,000

lines and a meter of books stacked

up like this is a million lines so that's a good metric

million lines of code per meter and stacked

up books and

the Empire State Building is

22,000 books high

and 440

million lines of code right

so if you've ever heard anybody heard

of any programming systems that have 400 million

lines of code yes

though come on

yeah

yeah take a look at our government sometime

in fact if you

look at your own little

own laptop if you happen to be running

Microsoft the operating system is about 120

million lines of code remember

system it hasn't done anything for you yet

just sitting there and then Microsoft

Office is over a hundred million lines of code

so that's

220 million lines

of code it's about eleven

thousand books of code

anybody ever read all that code

no way very

few people who read it all have read eleven

thousand books of anything I can guarantee

you read it all you're not going to read eleven thousand

books of code so most of the code has

never been over viewed by any

single person or even any single group in

fact much of the code in there is code

that isn't even run but they're afraid to take it out

hey don't know whether it's run or not and

this is it this is a problem on the

other hand of the

looking at it from the standpoint of writing

code the when you look at

the actual features you

this two hundred and twenty million lines of code it

doesn't seem like it should be should take two

hundred and twenty million lines of code just

shouldn't back the first time around it was done at Xerox PARC

did about half of this and it only took

ten thousand lines of code so something

happened some kind of explosion

of complications and complexity

and here just to

make you feel better I located a large financial products

company whose name I will not put here

that has more than 400 million lines

of code in its primary offerings

to its customers so this is what they

are actually maintaining and

you can tell they're a little old-fashioned because their user interface

is given in terms of screens which

harks back to the days of mainframes they

have 170,000 screens they

have to deal with and that's about twenty thousand

books or almost an

Empire State Building worth of code

however

if you're looking for a job if you came

to UCLA to learn to program and get a job it's

just this kind of stuff that you actually have to learn

about because that is what business is mired in

right now this is what they're hiring people this

is why they're crying for programmers

not to do better but

ake care of the mess that is already there think

about that

okay so

I'm going to stick to

I'll show you a couple of examples in the time

that's left of what might be done about this

part

of personal competed these several hundred millions of lines of

code okay so

let's take a look at this problem

from a slightly different perspective

over here we've got some

gates over

here we've got a problem

this is what we need we need

to do something over here and the question

is is what is it going to take us to get from there to there

these days and

so in

terms of machine code lots

of the kinds of things I'm talking about or literally billions

of lines of code because machine code is written one

instruction per line of code and

maybe C

gives eight to ten

machine code instructions per line

of code so maybe something that would be

billions would be hundreds of millions in

C and

we can imagine a

higher-level language than C

not the Java is that

much higher level language higher level

in C but could imagine something

higher level you can imagine something higher level imagine

something it might do a lot of these tasks in just

thousands of lines of code and the

question is why

do we stay here down

at the gear level for most of the

programmatic that is still done today and

this huh not

a lot of the organization of code at

is a little bit more like the way biology

organizes itself almost

none of this still being done

okay

so the programming effort comes

down as we go to higher and higher level

languages but

computer science has not

actually been

up to the challenge of putting in the amount

of invention that's necessary to make programming

systems that do this amount of work for us so

we can think of an in-between is

just a lot of work for any kind of programming language you do because there's

packaging there's documentation there's debuggers

there's an enormous amount of

work that has to be done and the

idea is that with more work which

gets tougher as you come this way you actually

reduce the general programming effort so this is

popular so virtually all of the programming in

business in the u.s. today is done

at this level still this is a level that

is really not different from the level of programming in the

60s almost nothing has changed

new languages have come along but they have not

up to their level in any significant way

but

just to go against

the tide here even though you're going to be studying

a lot of this stuff here I just want to make you aware of

these ideas down here which

if you're interested in research and in making things

better you might poke your head into

now what's funny

about history is that there

are people who are absolute geniuses who

transcend the time in which they

live so 50

years ago there

was no computer graphics this is the

guy who invented computer graphics and he

also invented object-oriented

design systems

so he actually did

the work in 62 and wrote it

up in 63 so this is still the 50th anniversary of this

I thought you'd like to see what this

very first interactive

graphic system looked like and what it could do

now the first thing you have to visualize is this guy is

sitting here with

a pointer in his hand a light pen but

he's in a computer that is about eight times maybe

ten times the size of this room

it was close to the size of

at least the first Fran's hall building

it had its own roof

it was the building and

it was an air defense computer and from

three o'clock in the morning to six o'clock in the morning they let this one guy

play around with it and

so here's what he did and

by the way this is not actually a computer display it just was

an oscilloscope that put up spots

so the first thing he had to do was to write

programs that would make lines and arcs

and and so forth and about

a third of the capacity of this enormous

machine was used just to make a simulated

graphics display because there were no graphics displays

okay so this

will give you an idea so

he gets some ink

and he just sketches in this flange

because look at he's pointing at it now and he's

giving it a constraint to make everybody mutually

perpendicular and what you saw

there was sketch pad solving the problem for him

right so this way

you program this system was by

telling it what you wanted to have true and sketch bad

and figure out how to have it be true same idea

here make these two guys parallel

now the constraint

is collinearity

put these lines down these

dashes I'm putting in here down on top of

the

now he says okay let's make the guidelines transparent

and now we've got a hole in the flange

and you

has continued assuming the first clipping window

ever done is that actually

the drawing is done on a sheet

of virtual paper about a third of a mile square

now he wants to make a rivet

he's

going to use the center here for the arc

and

now he's going to do the same trick he's going to say to these

guys take these guys to make them all

mutually poopin perpendicular that's going to drag the

cross pieces that's going to drag

the top of

the rivet now he's going to show

I'll start off with different

initial starting conditions and I'll still get something

that obeys the constraints that I gave it now

have put in absolute numbers in there you could have put in ratios

this

is why it's called sketchpad the

idea is you should be able to work quickly get

rough idea of it and then tell the computer the

rules that if they were solved was completed

okay now

he's showing that

what he drew is not

just a rivet but

it what it's what we call a class in an object-oriented

language which he called a master

so what he drew there was the master drawing

of a rivet and what he's manipulating

here is an instance of the rivet

so now he's

showing yeah I can make more instances

of the rivet and

I can make them different sizes and

so forth but he forgot

that cross P so he goes to the master makes

those guys transparent and we can see the rivet

feels the instances of the rivet feels those

things then the last

part of this demo is

that

he can take anything

that he's constructed and make

it into a master so now this is a master drawing

of a flange with a rivet in it

and now he's

making

instances of those okay

so this is a yes

go ahead

yeah

yeah in fact on the larger movie

which you can find online you can see

the sheet is populated with lots of different things

on it yes oh okay

okay so

so you have to realize this was a PhD

thesis this is done in one year by one person and

what the

contributions were is

first interactive computer graphics

object-oriented

design structures

constraints for programming

so you didn't program it using sequential code

at all and

one of the great

final things he did was to show

how you could make a bridge

simulation without sketchpad knowing about bridges

ahead of time because the whole point

was that sketch pad was not supposed to know ahead of time what

o try and do in it the

idea is you should be able to do everything and in fact the

all of these drawings were made by

sketch pad and the the text

here these each text figure is actually

a drawing and sketch pad so there's a master for

F and everywhere there's an F there's an instance

of it so the whole system was done and this

thing and I wants to ask Ivan how

could you have done computer graphics

object-oriented design and

constraint based programming all by yourself

year and he said well I didn't know it was hard

that's then okay so the

bridge there's no movie of the bridge because

it took the supercomputer back in

1962 about 20 seconds

for each time step on it

because of the computer power of this computer

size of a building was about that of a greeting card

today

but

to celebrate

the anniversary of this system

a couple of the guys at viewpoints Burke Freudenberg and

Yoshi Yoshi ki Oshima made

a version of this of

this bridge sketch

N and we put in the twinkling

there so it looked like the

display back then and so you can

move things in you

can turn on gravity

you can hang away from it

even when it

settles down

it has a really settle down if I turn

on the decimal points here see

it's still wiggling just

like wheel bridges do

and I can

interesting to watch what happens when

I stick this beam in

here take a look at the numbers of the

stress and strain around it when I drop this guy in here

and notice this

guy over on the Left felt that

ripple across

yeah so

one of the main

things that's got people going from sketchpad

most it was too hard for people to really

know what to do with but one

sure about was they need a better looking display so

here's the very same thing rendered with them

with a modern display and we can do a few more tricks like

we can

okay and we programmed this a little bit

differently than fact we've done this several times

now one of the students in this class last year

Matthew Goldberg what

did an internship with us

and did

a different version of this did

a nice job of it we

programmed it up in terms of

three constraints

not the same kind of constraints

used but a different kind of constraint for instance this

like it might have something to do with gravity so

this is way

to think of is this the three line program here

so if I turn this off

so

all we've got left is the spring tension here

should all null out which

it does so we'll turn gravity back on again

and

this bottom guy is

the constraint for these pins

so this bridge is pinned together and

if I turn off the pin constraint

that's holding everything together in this simulation