John Backus passes away... - test-drb@ccmp.vtda.org

21 Mar 2007

...
  From: "Chuck Guzis" <cclist at
sydex.com>

 On 21 Mar 2007 at 12:12, Roger Holmes wrote:

  I used Fortran 4 on the IBM 7094 at Imperial
College London. I
 remember one day the compiler reported: 
 I used FORTRAN II under FMS II on the 7090 but never saw a FORTRAN IV
 implementation there.  It's been entirely too long ago, but, as I
 recall, one punched a "B" in column 1 for boolean expressions, "D"
 for double-precision and "I" for complex, as FORTRAN II still relied
 on implicit typing for variables.

 One of the most diagnostic-bald versions of FORTRAN I ever used was
 the "USA BASIC FORTRAN" under DOS/360.  The thing couldn't have had
 more than about 10 diagnostic messages, most of them single-word. 
One of my bosses at Marconi Avionics thought that compilers should  
only have one error message because as a compiler cannot find all  
errors (such as a mistyped number), you should not rely on it to find  
errors in your programs. You should only ever submit 100% correct  
code to the compiler. I think he worked on the Jaguar aircraft's  
flight program, so there is some justification in that field where a  
software error could cause a fast jet to take out a street or two of  
a city.

...
   I was used to
syntax error messages by the dozen but this was the
 first time I had seen the compiler correct an error and run the  
 job. Of
 course we are  used to warnings now, but I think it was that one  
 which
 got me interested  enough in compilers to eventually get a job  
 writing
 them. 
 Pat could probably fill in details here, but Purdue for many years
 used 7090/94's to run a student variant of FORTRAN called PUFFT.  The
 basic idea was for the compiler to 'fix" as many errors as possible
 so that a program would run somehow.  I believe it was described by
 Saul Rosen in an ACM paper and republished in one of those
 "Programming Languages Survey" books.  IIRC, the 709x were also used
 as I/O front ends for the CDC 6600 there, which ran Purdue's own
 variant of MACE, rather than the more-or-less standard SCOPE.  Greg
 Mansfield was pretty proud of that. 
It was indeed PUFFT that I used, around 1969 when I was a schoolboy.

...
   If you stuck
to floating point and small numbers but there were big
 problems with word length variations when using integers. 
 IIRC, the 32-bit floating point word (with 4-bit normalization
 granularity) of S/360 cost IBM a bunch of business in the
 "scientific" world.  It had one of the lowest-precision FP
 representation of big iron at the time.  I believe that IBM
 eventually remedied this with "extended precision". 
Interesting. I guess that's why, after the 7094, the University of  
London used no(?) IBMs, just CDC and ICL machines until minis came  
along.

...
   I seem to
remember that some of the people who taught me to program
 considered Fortran to be too close to the 7094 instruction set, in
 particular they said the computed goto mapped directly onto a 7094  
 instruction and
 hence considered it to be not very universal, and to support it  
 would  be to
 assist IBM in its domination of the computer market. 
 That must have been some clever propganda on the part of someone!
 But conspiracy theories have always been popular.  Computed GOTOs
 weren't exactly the dominant feature of most programs--and they were
 implemented as simple indexed jumps for the most part--a feature
 scarcely unique to IBM hardware!

 For small systems, FORTRAN was amazingly useful.  The other day, I
 ran across some code that I wrote for CP/M to convert between ISIS-II
 and CP/M file formats--in FORTRAN.

 Compiler design has come a long way since.  In the 1970's, I recall
 that a co-worker pushed a PTR in front of my face that was, frankly,
 quite surprising.  CDC FTN for years allowed an alternative way of
 expressing Hollerith constants using any arbitrary delimiter
 character, so 5HCHUCK and H*CHUCK* were equivalent ways of expressing
 the same constant.  Most people used asterisks or the not-equal
 symbol (the standard character set didn't have quotation marks), but
 the compiler would allow just about anything.

 The statement in question looked something like this:

 100	FORMAT( HX)=(1+BX )

 Recall, that prior to FORTRAN 90, FORTRAN had no reserved words. 
Yes that does look weird at first sight.

Probably later version of Fortran were better, but version 4 was just  
so restrictive, after using Algol's For..Step..Until..Do.. with  
expressions, I could not really go back to Fortran IV's for  
statements with single, simple unsigned integer constants for the  
start, end and step values.

Roger.