Posted Feb 26, 2007 18:19 UTC (Mon) by MBR
In reply to: Exaggerated.
Parent article: How an Accident of Hardware Design Encouraged Open Source (O'ReillyNet)
I think you're misunderstanding the relevance of the IBM 360/370 to my point.
In the early 1980s, a number of startups wanting to build the next generation of desktop computers looked to Unix as an alternative to writing their own operating system from scratch because it was written in C rather than assembler. Many of them (e.g. Sun Microsystems) were using CPUs like the Motorola 68000 whose byte numbering scheme was exactly the same as that used by the IBM 360. Whether the Motorola engineers who designed the 68000 had copied this from the 360 or copied it from someone who copied it from someone who copied it from the 360 is impossible to say. This generation of computers all used ASCII. No-one in their right minds would have used EBCDIC, except for IBM who was stuck trying to maintain backward compatibility with their earlier offerings.
The PDP-11 is relevant because Unix had been rewritten from assembler into C on a PDP-11 in 1973. It had ported easily from DEC's PDP-11 to DEC's VAX because DEC designed had the VAX to be a grown-up PDP-11. The VAX followed the PDP-11's byte numbering scheme. By the early 1980s Unix was mature enough that a startup could consider using it for their OS.
The result was that programmers at countless Silicon Valley startups in the early 1980s found themselves constantly struggling to eliminate byte-order dependencies in C code as they ported Unix from one of the two standard VAX implementations, the Berkeley distribution or the Bell Labs distribution, to the new microcomputers. In comparison to the hordes of programmers in Silicon Valley, around Boston's Route 128, and elsewhere, who were porting code from ASCII-based little-endian machines to ASCII-based big-endian machines, the number of programmers porting code between EBCDIC-based IBM machines and these new machines was small. And so the former group had a much greater influence on common programming practice in the Unix world than the latter group.
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