Re: Ada Tutor Web Site Shutting Down

["Frank J. Lhota" <FrankLho.NOSPAM@rcn.com>]

On 5/13/2011 12:19 PM, Paul Colin Gloster wrote:
> Rugxulo<rugxulo@gmail.com>  sent on May 12th, 2011:
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> |"[..]                                                                     |
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> |DOS was used because of the extremely low RAM of the day (16 to 64 kb,    |
> |I think) on the original IBM PC. [..]                                     |
> |[..]                                                                      |
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> |[..]"                                                                     |
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>
> All IBM PCs had much more RAM than 64 kilobytes. A Commodore 64 had 64
> kilobytes and cost circa 10% as much as an IBM PC. Some Sinclair ZX81s
> and Sinclair ZX Spectrums (also branded as Timex instead of Sinclair)
> had 16 kilobytes of RAM and cost circa 1% and circa 3% as much as an
> IBM PC, respectively.

IBM PCs did have more than 64 KB, but they still suffered from severe 
memory limits. Memory provides an excellent example of Moore's law: in 
the 1980's, memory was an order of magnitude more expensive than it is 
now. Some PC's were equipped with as little as 256 KB low memory (that 
is, memory for the OS and applications).

Granted, many early mainframes had even tighter memory constraints, but 
many of these platforms could alleviate the memory shortage somewhat by 
using temporary disk space. The first PC's could not take this approach 
because disk space was even more limited than memory. The first PCs had 
no hard disk. Instead, they used low-density single-sided 5 1/4" 
floppies with a capacity of 180 KB.

MS-DOS has a lot of annoying limitations. But it is hard to imagine 
anyone doing something much better given the constraints of the platform 
that DOS was designed for.

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