Hello, im very new to ARM-GCC and c itself so i have two very basic questions. So "almost"-newbies have the pleasure to give an answer too. what does the "~" do ? example: VICIntSelect &= ~0x00000040; i was googling a lot but did not find anything at all related to "c" VICIntSelect is just a constant defined in the headerfile lpc2xxx.h #define VICIntSelect (*((volatile unsigned long *) 0xFFFFF00C)) das the commandline VICIntSelect = 0x00000040; mean: store value "0x00000040" in Memory-Adress "0xFFFFF00C" ? thank you very much for helpful answers greetings Stefan
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#1171864
Stefan Ludwig wrote: > what does the "~" do ? ~ (tilde) 1's complement in German: "Komplementierung aller Bits eines Integer-Wertes (NOT/Einer-Komplement)." Examples: ~00000000 == 11111111 ~11111111 == 00000000 ~11001101 == 00110010 Links http://www.schellong.de/c.htm#oper (German) http://www.lysator.liu.se/c/bwk-tutor.html#bit > VICIntSelect = 0x00000040; > mean: store value "0x00000040" in Memory-Adress "0xFFFFF00C" ? Yes. Another Stefan ;-)
Stefan Ludwig wrote: > i was googling a lot but did not find anything at all > related to "c" What did you googler on? Obviously typing '~' into google would not get you far! Googling of "C Operators" would have got you the answer - as would any good C reference (in fact even a bad reference!). Get yourself a copy of K&R for example. Clifford
Clifford Slocombe wrote: > Stefan Ludwig wrote: >> i was googling a lot but did not find anything at all >> related to "c" > What did you googler on? Obviously typing '~' into google would not get > you far! Googling of "C Operators" would have got you the answer - as > would any good C reference (in fact even a bad reference!). Get yourself > a copy of K&R for example. > > Clifford Just for the record, this is the response this ilicited from Stefan by privaed e-mail: ==================================== so you're just another one of this arrogant guys throwing around special TLA*s like "K&R" What if I even did not know that "~" is an OPERATOR? judging about your answer: NOT HELPFUL AT ALL just satisfying your frustration about what ever ==================================== I am sorry Stephan, if you found the response unhelpful. That was not the intention. I felt that the specific question had been adequately answered, so rather than duplicate the information I thought that perhaps a better approach to problem solving than posting to a forum might be helpful. Also the suggestion would have provided information on all the other C operators as well. It is interesting that you found that unhelpful. It did not seem unreasonable to me that if you are going to use a programming language that you should have some sort of language reference. "The C Programming Language" by Kernighan and Ritchie (K&R) is the seminal work on the language. It commonly referred to as K&R, and Google'ing on just that will certainly tell you what it is if you were not familiar. If you did not realise that '~' was an operator, than you don't really understand the syntax of C. All the more reason to get a reference.
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Another suggestion if you find a search engine does not work for you, is to head over to wikipedia which will always lead to a starting point to find out about such things. Good Luck with learning ANSI C, I have been using it for 18 years so I think I have the hang of it now!
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#1171868
I took some of my own medcine and found this :- http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B Not bad for 5 clicks! FordP wrote: > Another suggestion if you find a search engine does not work for you, is > to head over to wikipedia which will always lead to a starting point to > find out about such things. > > Good Luck with learning ANSI C, I have been using it for 18 years so I > think I have the hang of it now!