On 1999-09-11 [EMAIL PROTECTED] said:
>Sam Heywood wrote:
>> Back in the good old days of DOS version 1.0 and CPM, many
>>programs were written in which forms were processed under an
>>infinite loop routine which provided for a keyboard input of
>>"9999" as the "stop program" command, being the only valid
>>input for exiting the loop and ending the program. A computer
>>operator running such a program would encounter a prompt
>>stating "Enter the date". To stop the program and exit, the
>>operator would simply enter "9999". A program properly written
>>to work in this fashion would always execute just fine and
>>never produce any problems except in the special case in which
>>the operator intended to enter "9999" as a valid date, rather
>>than as a "stop program" command. During the era in which the
>>programs were written, everybody "assumed" (and you know what
>>this means) that the programs would have been superseded and
>replaced by new programs prior to September 9th, 1999.
>The key here is that you write "a keyboard input of "9999" as the
>"stop program" command". So the way to solve this is easy just
>don't enter that into the computer (and why not ask the computer
>for the date?). More to the point: (19)990909 doesn't contain four
>9:s (9999) in a row (imagine if we only had 9 months a year and 9
>days in each of them!) //Bernie
>http://hem1.passagen.se/bernie/ DOS programs, Star Wars ...
A program of the type described would continue to run provided
the operator refrained from entering "9999" at the "Enter the
date" prompt. However, the resulting printout would reflect an
invalid date if the actual date were Sept. 9th, 1999. As many
programs of this type were written for such purposes as producing
printouts of everybody's accounts on "interest paid to date",
"kilowatt hours used to date", "gallons used to date", "tons
delivered to date", and worker-production reports on "widgets
produced to date", payrolls, and summaries of daily business
transactions, it was very important that the printout should
reflect the valid date. The only easy way that I know of to
solve the problem would be to modify the source code so as to
provide for a different input for the "stop program" command.
I believe that most such programs were written in BASIC. I
myself even wrote programs of the type described. In those days,
an input of "9999" was often the "standard stop-program command".
The programs were designed so that a keyboard input having only 4
digits would default to the correct position on the input screen.
It was unnecessary to enter "090999" as the date. An input of
zero as the first or third digit simply wouldn't work. As for
building in a routine to ask the computer for the date, I don't
think this could have been done in the early versions of BASIC.
Programs of this type are still very useful today, but they
could not have worked on Sept. 9th, 1999.
Sam Heywood
Net-Tamer V 1.11.2 - Registered
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