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1. Top results related to how does ansi standard c differ from the language defined by this book pdf

   • How does the function getop() from "The C Programming Book" work?

     Top Answer

     Answered Jul 11, 2017 · 0 votes

     Lets break it down piece by piece:

     • while((s[0] = c = getch()) == ' ' || c == '\t') skips all spaces and tabulation from the beginning fo the string. At the end of this loop s[0] contains the first char which is not either of the two mentioned before.

     Now if c is something other than . or a digit we simply return that.

     if(!isdigit(c) && c != '.') { return c; }

     If c is not a digit we are done and it's quite right to set s[1] to null!

     Otherwise, if c is a digit we read as much digit chars as we can overwriting s from position 1. s[1] was '\0' but it does not matter because s[++i] would be s[1] at the very first iteration of

     i = 0; if(isdigit(c)) while(isdigit(s[++i] = c = getch()))

     so s is kept in a consistent status.

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     1/5

   • How does C differ from Java's compilation model?

     Top Answer

     Answered Nov 28, 2011 · 11 votes

     A proper answer to your question could take several hundred pages to answer, but I'll try to sum it up in a few paragraphs.

     Basically, the "classic compilation model" you refer to takes as input human-written source code and emits machine code, which can be loaded and run without further translation of the machine code. One ramification of this is that the resulting machine code can only be run on compatible hardware and can only be run within a compatible operating system.

     The Java compilation model takes human-written source code as input and emits not machine code, but so-called "byte code". Byte code cannot be directly executed on a machine. Instead, it needs to be translated once again by another compiler to machine code, or interpreted on-the-fly by a device that executes instructions on the machine that correspond to the instructions in the byte code. The latter device is often referred to as a Virtual Machine. One ramification of this model is that the byte code can be "run" on any platform that has either a byte code compiler or virtual machine written for it. This gives Java the appearance and effect of complete portability, where there is no such portability implied by the machine code emitted by a C++ compiler stack.

     Other Answers

     Answered Nov 28, 2011 · 8 votes

     Two aspects play into the C (and C++) compilation model. One is its longer history than Java, meaning that it caters to very low-powered compilers and machines. The second is the compilation target, which is usually low-level machine code.

     To target low-memory compiler environments, C code must be readable from top to bottom, with no backtracking. This means that you have to follow a strict discipline for the order of declarations. (C++ relaxes this a little bit for class definitions.) Further more, each source file must be compilable as an independent translation unit which need not know anything about other source files.

     Second, because C targets low-level machine code, this means that each translation unit contains essentially no metadata, in stark contrast to Java class files. This necessitates a stronger coding discipline in which each translation unit must be provided with the necessary declarations. The compiler cannot just scan all the other files in order to get the required information; it is up to the user to supply it. (C++ enforces this more rigidly, in C you can get away with nasty errors by forgetting a declaration.)

     Bear in mind that a C program has to be fully compiled and linked at compile time, so a lot of information has to be available already at that point. Java programs can load classes at runtime, and Java execution generally performs more "fitting" operations (casting, essentially, as opposed to static linking in C) at runtime. The more sophisticated runtime environment of Java allows for a more flexible and modular compilation model.

     Other Answers

     Answered Nov 28, 2011 · 1 votes

     I am going to be brave and compare performance. ;)

     The Java compiler javac does little optimisation preferring to syntax check code. It does all the reasonable checks required to ensure it will run on a JVM, and some constant evaluation and that's about it.

     Most of the smart compilation is done by the JIT which can perform dynamic complication based on how the program is used. This allows it to inline "virtual" methods, for example, even if the caller and callee are in different libraries.

     The C/C++ compiler performs significant static analysis up front. This means a program will run at almost full speed right from the start. The CPU performs some dynamic optimisation with instruction re-ordering and branch prediction. While C/C++ lacks dynamic optimisation, it gains from by making low level access to the system much easier. (Its usually not impossible in Java, but low level operations which are trivial in C/C++ can be complex and obscure in Java) It also provides more ways to do the same thing allowing you to choose the optimal solution to your problem.

     When Java is likely to be faster.

     • If your style of programming suits Java and you only use the sort of features Java supports, Java is likely to be marginally faster (due to dynamic compilation) i.e. you wouldn't use C/C++ to their full potential anyway.
     • If your code contains lots of dead code (possibly only known to be dead at run time) Java does a good job at eliminating this. (IMHO A high percentage of micro-benchmarks which suggest Java is faster than C++ are of this type)
     • You have a very limited time and/or resources to implement your application. (In which case an even higher level language might be better) i.e. You don't have time to optimise your code much and you need to write safe abstracted code.

     When C/C++ is likely to be faster.

     • If you use most of the functionality C/C++ provides. Something more advanced programmers tend to do.
     • If startup time matters.
     • If you need to be creative about algorithms or data structures.
     • If you can exploit a low level hardware feature, like direct access to devices.

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     2/5

   • How does this program continuously update and print the time from struct time in C++?

     Top Answer

     Answered Dec 04, 2020 · 0 votes

     If I had to summarize how it does its job in one word, I'd say "poorly".

     The standard library already has functions to do most of what it's doing, so if you just want to print out the current time in 12 hour format, you can do something like this:

     #include <iostream>#include <iomanip>#include <ctime>int main() { time_t n = std::time(nullptr); tm now = *localtime(&n); std::cout << std::put_time(&now, "%H:%M:%S\n");}

     As for the loop, that's presumably to continue printing out the time (constantly updated) until you kill the program. Probably author couldn't figure out what to tell the compiler to say: "Until the end of time", so they just used "forever".

     The if statements about foo<10 seem to be to fill in a leading 0, so (for example) 8 minutes after 9 will print as 9:08 rather than 9:8 (but the code I have above handles that automatically).

     As a side note: In my opinion (and I'm far from alone in this) localtime is rather poorly designed. The way I've used it above (immediately dereferencing the pointer it returns, and copying that tm into a new one) helps minimize the frequency of the problems it causes, but if you have it available, localtime_r is preferred.

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     3/5

   • C++20: How is the returning from atomic::wait() guaranteed by the standard?

     Top Answer

     Answered Dec 04, 2021 · 5 votes

     #1 is pretty much addressed by C++20 thread possibly waiting on std::atomic forever. The wait() operation is clearly eligible to be unblocked by the notify(), and is the only such operation, so the notify() must unblock it. The eligible "wait operation" is the entire call, not only step 30.3.

     If an implementation performs steps 30.1-3 in a non-atomic fashion, such that the notify can happen "between" steps 1 and 3, then it has to somehow ensure that step 3 unblocks anyway.

     #2 is stickier. At this point I think you are right: the standard doesn't guarantee that the second load gets the value 1; and if it doesn't, then it will presumably block again and never be woken up.

     The use of the relaxed memory ordering makes it pretty clear in this example. If we wanted to prove that the second load must see 1, the only way I can see is to invoke write-read coherence (intro.races p18) which requires that we prove the store happens before the load, in the sense of intro.races p10. This in turn requires that somewhere along the way, we have some operation in one thread that synchronizes with some operation in the other (you can't get inter-thread happens before without a synchronizes with, unless there are consume operations which is not the case here). Usually you get synchronizes with from a pairing of an acquire load with a release store (atomics.order p2), and here we have no such thing; nor, as far as I can tell, anything else that would synchronize. So we don't have a proof.

     In fact, I think the problem persists even if we upgrade to seq_cst operations. We could then have both loads coherence-ordered before the store, and the total order S of atomics.order p4 would go "first load, second load, store". I don't see that contradicting anything. We would still have to show a synchronizes with to rule this out, and again we can't. There might appear to be a better chance than in the relaxed case, since seq_cst loads and stores are acquire and release respectively. But the only way to use this would be if one of the loads were to take its value from the store, i.e. if one of the loads were to return 1, and we are assuming that is not the case. So again this undesired behavior seems consistent with all the rules.

     It does make you wonder if the Standard authors meant to require the notification to synchronize with the unblocking. That would fix the problem, and I would guess real-life implementations already include the necessary barriers.

     But indeed, I am not seeing this specified anywhere.

     The only possible way out that I can see is that "eligible to be unblocked" applies to the entire wait operation, not just to a single iteration of it. But it seems clear that the intent was that if you are unblocked by a notify and the value has not changed, then you block again until a second notify occurs (or spurious wakeup).

     It's starting to look to me like a defect.

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     4/5

   • How does the ActiveRecord pattern differ from the Domain Object or Data Mapper pattern?

     Top Answer

     Answered Dec 04, 2023 · 22 votes

     The main difference between the two patterns is this:

     • In the ActiveRecord you have one domain object that both knows all the business logic and how to save/update itself in the database, user.getLinkToProfile() and User::find(1) , User::save(user)
     • In the DataMapper pattern you have one domain object that holds all the business logic, for exmaple user.getLinkToProfile() (or something similar) but knows nothing about the database in question, in addition to this you have a mapper-object that is responsible for saving, updating, selecting, etc. user objects from the database which would have UserMapper::find(1) , UserMapper.save(user)

     DataMapper is potentially more complex then ActiveRecord but it's a lot easier to develop your domain model and database asynchronous than with ActiveRecord.

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     5/5

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2. archive.org › details › the-ansi-c-programmingThe ANSI C Programming Language : Brian W. Kernighan, Dennis ...

   archive.org › details › the-ansi-c-programming

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   Apr 19, 2021 · Written by the developers of C, this new version helps readers keep up with the finalized ANSI standard for C while showing how to take advantage of C's rich set of operators, economy of expression, improved control flow, and data structures.

3. stackoverflow.com › questions › 17206568What is the difference between C, C99, ANSI C and GNU C?

   stackoverflow.com › questions › 17206568

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   May 22, 2017 · ANSI C : The first C language was standardized by the body called ANSI in 1989 that's why it is called c89. C99 : with the demand from the developers requirements, in 1999-2000 further or additional keywords and features have been included in C99 (ex: inline, boolean..

   • Everything before standardization is generally called "K&R C", after the famous book (1st edition and 2nd edition), with Dennis Ritchie, the invent...
   • I MUST respond regarding ANSI C. Although ANSI has not done anything with it, compilers are still built to it.
   • In Addition To Lundin Answer. Here is What Dennis Richie Has To Say When Asked. "Why didn't K&R wait for the final, approved ANSI standard before...

4. venkivasamsetti.github.io › ebookwormThe C programming Language - GitHub Pages

   venkivasamsetti.github.io › ebookworm

   This Second Edition of The C Programming Language describes C as defined by the ANSI standard. Although we have noted the places where the language has evolved, we have chosen to write exclusively in the new form. For the most part, this makes no significant difference; the most visible change is the new form of function declaration and definition.

5. archive.org › details › brian-wBrian W. Kernighan, Dennis M. Ritchie The ANSI C Programming ...

   archive.org › details › brian-w

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   Aug 12, 2023 · An icon used to represent a menu that can be toggled by interacting with this icon.

6. www.gnu.org › software › gnu-c-manualThe GNU C Reference Manual

   www.gnu.org › software › gnu-c-manual

   This is a reference manual for the C programming language as implemented by the GNU Compiler Collection (GCC). Specifically, this manual aims to document: The 1989 ANSI C standard, commonly known as “C89” The 1999 ISO C standard, commonly known as “C99”, to the extent that C99 is implemented by GCC

   • File Size: 550KB

   • Page Count: 91

7. www.cs.princeton.edu › 2ANSI C Programming Language - Princeton University

   www.cs.princeton.edu › 2

   1995 D. Hanson, K. Li & J.P. Singh Computer Science 217: ANSI C Programming Language Page 14 September 7, 1997 ANSI C Programming Language • A small, general-purpose, initially systems programming language • Used for writing the UNIX OS and tools for many computers • Now also very popular for general-purpose computing • A “low-level ...

8. People also ask

   How does ANSI standard C differ from the language defined by this book?

   • Most often these comments highlight ways in which ANSI Standard C differs from the language defined by the first edition of this book, or from refinements subsequently introduced in various compilers. program consists of one or more translation units stored in files. It is translated in several phases, which are described in Par.A.12.

   The C programming Language - GitHub Pages

   venkivasamsetti.github.io/ebookworm.github.io/Books/cse/C Programming Language (2nd Edition).pdf

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   What's new in ANSI C 2nd edition?

   • This 2nd edition has been completely rewritten with additional examples and problem sets to clarify the implementation of difficult language constructs. 7 x 9 1/4. Presents a complete guide to ANSI standard C language programming. Written by the developers of C, this new version helps readers keep up with the finalized...

   The ANSI C Programming Language - Archive.org

   archive.org/details/the-ansi-c-programming-language-by-brian-w.-kernighan-dennis-m.-ritchie.org

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   What is ANSI C language?

   • ANSI C : The first C language was standardized by the body called ANSI in 1989 that's why it is called c89. with the demand from the developers requirements, in 1999-2000 further or additional keywords and features have been included in C99 (ex: inline, boolean.. Added floating point arthematic library functions)

   What is the difference between C, C99, ANSI C and GNU C?

   stackoverflow.com/questions/17206568/what-is-the-difference-between-c-c99-ansi-c-and-gnu-c

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   What are ANSI standard C comments?

   • Throughout this manual, commentary material is indented and written in smaller type, as this is. Most often these comments highlight ways in which ANSI Standard C differs from the language defined by the first edition of this book, or from refinements subsequently introduced in various compilers.

   The C programming Language - GitHub Pages

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9. ptgmedia.pearsoncmg.com › 0131103628Preface to the Digital Edition - pearsoncmg.com

   ptgmedia.pearsoncmg.com › 0131103628

   This second edition of The C Programming Language describes C as defined by the ANSI standard. Although we have noted the places where the language has evolved, we have chosen to write exclusively in the new form. For the most part, this makes no significant difference; the most visible change is the new form of function declaration and definition.