of a language. I looked at my book and
I found excerpts from several dozen
pages where I thought it gave all the variety of things I need in the book. Then
I sat down and I thought, well, if I were
Phyllis, how would I like to key this in?
What would be a reasonable format
that would appeal to Phyllis, and at the
same time something that as a compiler writer I felt I could translate into
the book? Because TeX is just another
kind of a compiler; instead of going
into machine language you’re going
into words on a page. That’s a different
output language, but it’s analogous to
recognizing the constructs that appear
in the source file.
the programming turned out
to be harder than he thought.
I showed the second version of the design to two of my graduate students,
and I said, “Okay, implement this,
please, this summer. That’s your summer job.” I thought I had specified a
language. To my amazement, the students, who were outstanding students,
did not complete it. They had a system
that was able to do only about three
lines of TeX. I thought, “My goodness,
what’s going on? I thought these were
good students.” Later I changed my
attitude, saying, “Boy, they accomplished a miracle.” Because going
from my specification, which I thought
was complete, they really had an impossible task, and they had succeeded
wonderfully with it. These guys were
actually doing great work, but I was
amazed that they couldn’t do what I
thought was just sort of a routine task.
Then I became a programmer in earnest, I had to do it.
this experience led to general
observations about programming
When you’re doing programming, you
have to explain something to a computer, which is dumb. When you’re
writing a document for a human being
to understand, the human being will
look at it and nod his head and say,
“Yeah, this makes sense.” But there
are all kinds of ambiguities and vagueness that you don’t realize until you
try to put it into a computer. Then all
of a sudden, almost every five minutes
as you’re writing the code, a question
comes up that wasn’t addressed in the
specification. “What if this combination occurs?” It just didn’t occur to
the person writing the design specification. When you’re faced with doing
the implementation, a person who
has been delegated the job of working
from a design would have to say, “Well,
hmm, I don’t know what the designer
meant by this.”
It’s so hard to do the design unless
you’re faced with the low-level aspects
of it, explaining it to a machine instead of to another person. I think it
was George Forsythe who said, “People
have said you don’t understand something until you’ve taught it in a class.
The truth is you don’t really understand something until you’ve taught it
to a computer, until you’ve been able
to program it.” At this level, programming was absolutely important.
When I got to actually programming TeX, I had to also organize it so
that it could handle lots of text. I had to
develop a new data structure in order
to be able to do the paragraph coming
in text and enter it in an efficient way.
I had to introduce ideas called “glue,”
and “penalties,” and figure out how
that glue should disappear at bound-
“i wake up in the
an idea, and it
makes my day
to think of adding
a couple of lines
to my program.
it gives me a real
high. it must be
the way poets
feel, or musicians,
does that for me.”
aries in certain cases and not in others. All these things would never have
occurred to me unless I was writing the
Edsger Dijkstra gave this wonderful
Turing lecture early in the 1970s called
“The Humble Programmer.” One of
the points he made in his talk was that
when they asked him in Holland what
his job title was, he said, “
Programmer,” and they said, “No, that’s not a
job title. You can’t do that; programmers are just coders. They’re people
who are assigned like scribes were in
the days when you needed somebody
to write a document in the Middle
Ages.” Dijkstra said no, he was proud
to be a programmer. Unfortunately, he
changed his attitude completely, and I
think he wrote his last computer program in the 1980s.
I checked the other day and found I
wrote 35 programs in January, and 28
or 29 programs in February. These are
small programs, but I have a compulsion. I love to write programs. I think
of a question that I want to answer, or
I have part of my book where I want
to present something, but I can’t just
present it by reading about it in a book.
As I code it, it all becomes clear in my
head. The fact that I have to translate
my knowledge of this method into
something that the machine is going
to understand forces me to make that
knowledge crystal-clear in my head.
Then I can explain it to somebody
else infinitely better. The exposition
is always better if I’ve implemented it,
even though it’s going to take me more
It didn’t occur to me at the time
that I just had to program in order to
be a happy man. I didn’t find my other
roles distasteful, except for fundrais-ing. I enjoyed every aspect of being a
professor except dealing with proposals, which was a necessary evil. But I
wake up in the morning with an idea,
and it makes my day to think of adding a couple of lines to my program. It
gives me a real high. It must be the way
poets feel, or musicians, or painters.
Programming does that for me.
the teX project led to
metafont for the design of fonts.
But it also wasn’t smooth sailing.
Graphic designers are about the nicest people I’ve ever met in my life. In