11 Sep
2022
11 Sep
'22
7:30 p.m.
Anecdote prompted by the advent of Burroughs in this thread:
At the 1968 NATO conference on Software Engineering, the discussion
turned to language design strategies. I noted that the design of Algol
68, for example, presupposed a word-based machine, whereupon Burroughs
architect Bob Barton brought the house down with the remark, "In the
beginning was the Word, all right--but it was not a fixed number of
bits!"
[Algol 68's presupposition is visible in declarations like "long long
long ... int". An implementation need support only a limited number of
"longs", but each supported variety must have a definite maximum
value, which is returned by an "environment enquiry" function. For
amusement, consider the natural idea of implementing the longest
variety with bignums.]
Doug
11 Sep
11 Sep
9:08 p.m.
New subject: Does anybody know the etymology of the term "word" as in collection of bits?
On Sun, Sep 11, 2022 at 9:31 AM Douglas McIlroy <
douglas.mcilroy(a)dartmouth.edu> wrote:
[Algol 68's presupposition is visible in
declarations like "long long
long ... int". An implementation need support only a limited number of
"longs",
To clarify things for A68 n00bs, you can *write* an indefinite number of
"longs", but after an implementation-defined point they don't add any
further range (and/or precision in the case of floats). This is true in a
truncated way in C as well, where "long" (which is the same as "long
int")
may be the same as "int".
but each supported variety must have a definite
maximum
value, which is returned by an "environment enquiry" function. For
amusement, consider the natural idea of implementing the longest
variety with bignums.]
In actual bignum implementations, there is a biggest bignum, but it may not
be possible to actually construct it. In GMP using 64-bit digits, it is
theoretically 2^((2^31 - 1) * (2^64 - 1)), or
2^39,614,081,238,685,424,720,914,939,905, which is Very Big Indeed. But
there is nothing preventing an implementer from watching intermediate
results and throwing an exception if they get too big.
9:30 p.m.
New subject: Does anybody know the etymology of the term "word" as in collection of bits?
On Sep 11, 2022, at 6:30 AM, Douglas McIlroy <douglas.mcilroy(a)dartmouth.edu> wrote:
[Algol 68's presupposition is visible in declarations like "long long
long ... int". An implementation need support only a limited number of
"longs", but each supported variety must have a definite maximum
value, which is returned by an "environment enquiry" function. For
amusement, consider the natural idea of implementing the longest
variety with bignums.]
It would be natural to use a Kleene star to represent an arbitrarily
long string of LONGs -- "long* int" -- though AFAIK Algol68 doesn't
do bignums. Weirdly even most 21st century progamming languages do
not provide built-in support for bignums!
C's INT_MAX, LONG_MAX etc are kind of an environment enquiry...
9:45 p.m.
New subject: Does anybody know the etymology of the term "word" as in collection of bits?
On 9/11/22, Bakul Shah <bakul(a)iitbombay.org> wrote:
C's INT_MAX, LONG_MAX etc are kind of an environment enquiry...
What size to use in C for int and long (pointers had to be 64-bit; no
issue there) was a big headache for DEC in the migration of Unix
(Ultrix) from VAX to Alpha. The first C compiler implementation used
ILP64 (64 bits for int, long, and pointer) and ran afoul of a lot of
code that assumed an int was 32 bits. ILP64 vs. LP64 because as
divisive an issue as the big-endian vs. little-endian debate.
-Paul W.
10:20 p.m.
New subject: Does anybody know the etymology of the term "word" as in collection of bits?
On Sun, 11 Sep 2022, Paul Winalski wrote:
On 9/11/22, Bakul Shah <bakul(a)iitbombay.org>
wrote:
When I first wrote C code I *assumed* things that were only necessarily
true on the platform I learned on (char=8, short=16, long=32; int=16,
pointer could be either 16 or 32, requiring the addition of the keywords
"near" and "far").
(I'm glad C99 introduced <stdint.h>, but on that platform the only C99
compiler is OpenWatcom.)
-uso.
C's INT_MAX, LONG_MAX etc are kind of an environment enquiry...
What size to use in C for int and long (pointers had to be 64-bit; no
issue there) was a big headache for DEC in the migration of Unix
(Ultrix) from VAX to Alpha. The first C compiler implementation used
ILP64 (64 bits for int, long, and pointer) and ran afoul of a lot of
code that assumed an int was 32 bits. ILP64 vs. LP64 because as
divisive an issue as the big-endian vs. little-endian debate.
-Paul W.
833
days inactive
833
days old
4 comments
5 participants
participants (5)
-
Bakul Shah -
Douglas McIlroy -
John Cowan -
Paul Winalski -
Steve Nickolas