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mecej4
Joined: 31 Oct 2006 Posts: 1901
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Posted: Sat May 02, 2015 7:41 pm Post subject: |
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The form IF (arith_expr) nnn, 0, 0 (with '0' standing for 'next line') is new to me. Perhaps, by several decades, this convention predates but closely resembles the instruction-pointer-relative addressing used in the x86 and other processors.
With that special meaning assigned to the label 0, should a card fall out of the hopper while the deck was being read in, you would get no "missing label nnn" error from the compiler at all, and run-time behavior could be mysterious. I can see that in this situation having card sequence numbers would be vital.
Last edited by mecej4 on Mon Jun 06, 2016 7:09 pm; edited 1 time in total |
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LitusSaxonicum
Joined: 23 Aug 2005 Posts: 2415 Location: Yateley, Hants, UK
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Posted: Sun May 03, 2015 11:46 am Post subject: |
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No doubt early Fortran statement types were aligned to processor instructions as one step beyond assembly languages, as distinct from (say) Algol which provides tools to describe algorithms in a standard way. The arithmetic IF goes right back to the beginning.
ICL's zero statement number was an innovative way to reduce the plethora of statement numbers, but it was an extension that no one else adopted. Like all extensions, once you used it on a large scale it impeded transferring the source code to another manufacturer's computers.
The nature of cards was that dropping just one was rather improbable. Drop a box of 2000 at the top of a 5-storey staircase (without risers) - done that. Shred one? Sure. Throw 500 into the air with a high-speed reader jam - that too. The only time I've lost just one line of code was when it was highlighted (but off screen) in a text editor and I pressed another key. It's over 30 years since I used cards, and over 20 since I threw them out.
Eddie |
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PaulLaidler Site Admin
Joined: 21 Feb 2005 Posts: 8255 Location: Salford, UK
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Posted: Mon Jun 06, 2016 4:10 pm Post subject: |
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The original failure has now been fixed for the next release. |
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