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- Newsgroups: alt.sys.pdp8
- Path: sparky!uunet!psinntp!news.columbia.edu!watsun.cc.columbia.edu!lasner
- From: lasner@watsun.cc.columbia.edu (Charles Lasner)
- Subject: Re: The good old days.
- Message-ID: <1992Nov22.194547.3976@news.columbia.edu>
- Sender: usenet@news.columbia.edu (The Network News)
- Nntp-Posting-Host: watsun.cc.columbia.edu
- Reply-To: lasner@watsun.cc.columbia.edu (Charles Lasner)
- Organization: Columbia University
- References: <1992Nov19.102634.20745@vpnet.chi.il.us> <1992Nov20.042652.18263@news.columbia.edu> <1992Nov22.050516.19990@vpnet.chi.il.us>
- Date: Sun, 22 Nov 1992 19:45:47 GMT
- Lines: 46
-
- In article <1992Nov22.050516.19990@vpnet.chi.il.us> cgordon@vpnet.chi.il.us (gordon hlavenka) writes:
- >
- >This means you have more?
-
- Not too many more for just a CPU per se.
-
- Here's one that came up in another newsgroup:
-
- Assume that there is a test location CHAR containing an arbitrary ASCII
- character. (If symbolic gets in the way, then assume it's location 0020,
- i.e., CHAR=0020.)
-
- Starting at 0200, write the shortest piece of code that can prove that the
- contents of CHAR are in fact within the range of printable octal digits, i.e,
- are in the range 0060-0071. Assume the worst, i.e., the contents could be
- junk. The idea is to do something which contains:
-
- *200
-
- START, CLA CLL /CLEAN UP
- {whatever you need}
- TAD CHAR /GET THE POTENTIAL CHARACTER WE ARE TESTING
- {test it somehow}
- JMP BAD /JUMP THERE IF NOT AN OCTAL DIGIT
- / COMES HERE IF THE CHARACTER WAS GOOD.
- HLT /THIS IS PAST THE CHALLENGE
-
- BAD, HLT /COMES HERE WHEN CHAR AIN'T AN OCTAL DIGIT
-
- Literally any 12-bit value might be in CHAR, but we want to weed out the
- "good" values as defined. The idea is to write the MINIMUM amount of code
- to check for the good vs. the bad (and the ugly). You supply the stuff that
- belongs in place of the stuff inside of {} in both places.
-
- Note: the AC is allowed to be "dirty" when you get to BAD.
-
- When the CHAR is acceptable, it falls through for more processing, etc, so I
- have merely placed a HLT there. Similarly, the "bad" values, having been
- isolated can be further processed at BAD, so I have merely placed a HLT there
- as well. (Hint: the AC=0000 through 0007 depending on whether the original
- CHAR value was "0" through "7".)
-
- On an scale of 1-10, this problem has a difficulty rating of 6.
-
- cjl
-
-