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发信人: tang (独孤九剑〖玄铁重剑〗), 信区: Program
标 题: Bjarne Stroustrup's FAQ(About C++)
发信站: BBS 荔园晨风站 (Mon Mar 20 12:07:15 2000), 站内信件
Bjarne Stroustrup's FAQ
These are questions that people ask me often. If you have better questions or
comments on the answers, feel free to email me bs@research.att.com. Please
remember that I can't spend all of my time improving my homepages.
Index
How do you pronounce "Bjarne Stroustrup?"
Can I ask you a question?
What is the best book to learn C++ from?
How long does it take to learn C++?
Knowing C is a prerequisite for learning C++, right?
Should I learn Smalltalk before C++ to become a real OO programmer?
How do I start learning C++?
Will you help me with my homework?
Where can I get a free C++ compiler?
You are Swedish?
What's the best way to improve my C++ programs?
Does it matter which programming language I use?
Did the ANSI/ISO standards committee spoil C++?
When will we have a C++ standard?
Where can I get a machine-readable version of the standard?
Are there any features you'd like to remove from C++?
When will we have a new ARM?
When will you publish a 4th edition of "The C++ Programming Language"?
Should I buy the "Special Edition" of "The C++ Programming Language"?
Is ``int* p;'' right or is ``int *p;'' right?
What C++ compiler do you recommend? Which libraries?
Is Java the language you would have designed if you didn't have to be
compatible with C?
Do you really recommend Ada over C++ for larger projects?
Would you compare C++ to "some language"?
Others do compare their languages to C++; doesn't that annoy you?
You won't compare C++ to other languages, but you write diatribes about C++?
C is better than C++ for small projects, right?
Is C a subset of C++?
What is the difference between C and C++?
When was C++ invented?
Why did you invent C++?
Why doesn't C++ have garbage collection?
Why is the code generated for the "Hello world" program ten times larger for
C++ than for C?
What do you think of EC++?
C++ got its Object-Oriented concepts from Smalltalk?
Is C++ an Object-Oriented language?
Did you really say that?
Did you really give an interview to IEEE?
Why is the language called C++?
Is the number of C++ users still doubling every year?
What are you working on now?
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How do you pronounce "Bjarne Stroustrup?"
It can be difficult for non-Scandinavians. The best suggestion I have heard yet
was "start by saying it a few time in Norwegian, then stuff a potato down your
throat and do it again :-)" Here is a wav file.
For people who can't receive sound, here is a suggestion: Both of my names are
pronounced with two syllables: Bjar-ne Strou-strup. Neither the B nor the J in
my first name are stressed and the NE is rather weak so maybe Be-ar-neh or
By-ar-ne would give an idea. The first U in my second name really should have
been a V making the first syllable end far down the throat: Strov-strup. The
second U is a bit like the OO in OOP, but still short; maybe Strov-stroop will
give an idea.
Yes, this probably is the most frequently asked question :-)
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Can I ask you a question?"
Certainly. I try to answer my email. However, please try to avoid asking a
question that is answered in my homepages. Also, please don't rely on a prompt
answer. I get a *lot* of email.
Here are links to
biographical information
C++ information and links
papers (incl. a few that can be downloaded)
books (incl. reviews and a few chapters that can be downloaded)
interviews
--------------------------------------------------------------------------------
What is the best book to learn C++ from?
There is no one book that is best for every person. There couldn't be one.
People are too different in the way they learn, in what they already know, in
what they need, in what they want, and in what kind of effort they are willing
to make. For people who are programmers and willing to learn new concepts and
techniques from a classical textbook, I recommend The C++ Programming Language
(3rd edition). It describes "pure C++," that is, the language independently of
any particular software development environment or foundation library (except
the standard library, of course). If that is not the right approach for you,
there are many other excellent C++ books.
See a note about the structure, contents, and aims of "The C++ Programming
Language (3rd edition)": The book is aimed at programmers with some experienced
and a wish to master C++. It is not aimed for non-programmers trying to learn
their first programming language or casual programmers trying to gain a
superficial understanding of C++ as fast as possible. Consequently, this book
focuses on concepts and techniques and goes to some pain to be complete and
precise.
If you want to know why C++ is the way it is, have a look at The Design and
Evolution of C++ (D&E). Understanding the design criteria and constraints helps
writing better programs.
Have a look at the ACCU (The Association of C and C++ Users) site. This is one
of the best sites for book recommendations by experienced programmers who are
not afraid to speak their mind (booksellers tend to give rosy reviews, and
reviews of the form "This book is perfect, I love it, I have read almost three
chapters, and can't wait to read more" are worse than useless - why anyone
would take advice on how to learn C++ from someone who completely lacks C++
experience beats me). The ACCU rates books for level of experience required and
overall quality.
--------------------------------------------------------------------------------
How long does it take to learn C++?
That depends on what you mean by "learning." If you are a Pascal programmer,
you can easily learn enough of the basic types, control structures, and library
functions to be effective at what you were effective at using Pascal. Will it
take a day or a week? That depends on you and the approach you take. I have
seen both and even wider variations. If you are a C programmer you can learn
enough C++ to make you more effective at C-style programming in a day.
On the other hand, if you want to be fully comfortable with all the major C++
language constructs, with data abstraction, Object-Oriented programming,
generic programming, Object-Oriented design, etc., you can easily spend a year
or two - if you aren't already acquainted with those techniques.
Is that then the time it takes to learn C++? Maybe, but then again, that is the
timescale we have to consider to become better designers and programmers. If a
dramatic change of the way we work and think about building systems isn't our
aim, then why bother to learn a new language? Compared to the time required to
learn to play the piano well or to become fluent in a foreign (natural)
language, learning a new and different programming language and programming
style is easy.
For more observations about learning C++ see D&E or a note from comp.lang.c++
that I wrote some time ago.
--------------------------------------------------------------------------------
Knowing C is a prerequisite for learning C++, right?
Wrong. The common subset of C and C++ is easier to learn than C. There will be
less type errors to catch manually (the C++ type system is stricter and more
expressive), fewer tricks to learn (C++ allows you to express more things
without circumlocution), and better libraries available. The best initial
subset of C++ to learn is not "all of C".
See Learning Standard C++ as a New Language for a discussion of the choice of
C++ constructs, techniques, and libraries for early learning.
--------------------------------------------------------------------------------
Should I learn Smalltalk before C++ to become a real OO programmer?
No. If you want to learn Smalltalk, learn Smalltalk. It is a most interesting
language and system, and learning something new is almost always a good idea.
However, Smalltalk isn't C++ and writing Smalltalk-style code in C++ is often
sub-optimal and frustrating. If you want to become a good C++ programmer and
don't have a few months to spare, concentrate on C++ and the concepts it
embodies.
--------------------------------------------------------------------------------
How do I start learning C++?
Naturally, that strongly depends on what you already know and your reasons for
learning C++. If you are a novice at programming, I strongly recommend that you
find an experienced programmer to help you. Otherwise, the inevitable mistakes
about language concepts and practical problems with the implementation you use
can magnify into serious frustrations.
You'll need a textbook for learning C++. This is the case even when your
implementation comes with ample on-line documentation. The reason is that
language and library documentation together with sample code are not good
teachers of concepts. Typically such sources are silent about why things are
the way they are and what benefits you can expect (and which you shouldn't
expect) from a technique. Focus on concepts and techniques rather than
language-technical details.
When choosing a book, look for one that presents Standard C++ and use the
standard library facilities in an integrated manner from the start. For example,
a reading a string from input should look something like
string s; // Standard C++ style
cin >> s;
and not like this
char s[MAX]; /* Standard C style */
scanf("%s",s);
Look for book recommendations from programmers with solid C++ experience.
Remember that no one book is the best for everyone. Have a look at the book
reviews the ACCU (The Association of C and C++ Users) site.
Aim to write idiomatic C++: avoid simply writing code in the style of your
previous language using C++ syntax; there is little to be gained from simply
changing syntax. See Learning Standard C++ as a New Language a discussion of
how one might approach C++.
--------------------------------------------------------------------------------
Will you help me with my homework?
No. Sorry. I don't do (other people's) homework. I get too many requests for
help with homework and help with finding bugs in student programs to be able to
find the time. Anyway, having a distant expert fix your programs is not the
best way to learn. Try finding a local person with C++ experience that you can
ask for guidance. A good mentor is the best help a student can have; maybe that'
s why they are not easy to find.
--------------------------------------------------------------------------------
Where can I get a free C++ compiler?
Try Cygwin from Cygnus, Djgpp, or Borland5.5. All are aimed at Wintel boxes.
These compilers are trying hard for ISO Standards compliance.
For Macs, see Apple.
Caveat: If you want to use "free" compilers for commercial work, be sure to
read all legal rules and restrictions attached.
There are a variety of old C++ implementations floating around on the web and
on CDs. I do not recommend an old C++ compiler for learning C++ or for new
production use. There is little gained by fighting your way through bugs that
have been fixed years ago or limitations that have been lifted years ago by the
standard committee.
For good quality free (parts of) the standard library, see SGI's STL site and
STLport.
--------------------------------------------------------------------------------
You are Swedish?
No. I'm Danish. have a look at my biography.
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What's the best way to improve my C++ programs?
I couldn't say. That depends on how you use it. Most people underestimate
abstract classes and templates. Conversely, most people seriously overuse casts
and macros. Have a look at one of my papers or books for ideas. One way of
thinking of abstract classes and templates is as interfaces that allow a more
clean and logical presentation of services than is easy to provide through
functions or single-rooted class hierarchies.
--------------------------------------------------------------------------------
Does it matter which programming language I use?
Yes, but don't expect miracles. Some people seem to believe that a programming
language can or at least should solve most of their problems with system
building. They are condemned to search forever for the perfect programming
language and become repeatedly disappointed. Others dismiss programming
languages as unimportant "implementation details" and put their money into
development processes and design methods. They are condemned to program in
COBOL, C, and proprietary design languages forever. A good language - such as
C++ - can do a lot for a designer and a programmer, as long as its strengths
and limitations are clearly understood and respected.
--------------------------------------------------------------------------------
Did the ANSI/ISO standards committee spoil C++?
No. They/we did a good job. You can quibble with details (and I do), but I'm
happy with the language and the new standard library. ISO C++ is a better and
more coherent language than earlier versions of C++. You can write much more
elegant and maintainable C++ programs today than was possible when the
standards process started. The new standard library is also a real boon. The
provision of strings, lists, vectors, maps, and basic algorithms for such
fundamental types makes a major difference to the way one can approach C++. See
the library chapters of The C++ Programming Language (3rd edition) (postscript
and pdf of Chapter 3: "A Tour of The Standard Library" is available
electronically), or one of my recent papers.
--------------------------------------------------------------------------------
When will we have a C++ standard?
We have one! The final technical vote took place November 14, 1997, about
10:30am. See a press release from the ISO C++ standards committee. After the
technical vote, the standard was ratified by a 22-0 national vote. The standard
is ISO/IEC 14882.
This is the language and standard library described in The C++ Programming
Language (3rd edition). The C++ compiler and library suppliers are already
shipping implementations that are quite close to the draft standard.
--------------------------------------------------------------------------------
Where can I get a machine-readable version of the standard?
The C++ standard (ISO/IEC 14882) is available for downloading at the National
Committee for Information Technology Standards Electronic Store. The cost is
(as I write this) US$18.00 payable on-line via credit card. The downloaded
document is in PDF form, 2794KB total size.
The draft standard as it were in later stages of the standards process can be
downloaded for free.
Be warned that the standard is not a tutorial; even expert programmers will do
better learning about C++ and new C++ features from a textbook.
--------------------------------------------------------------------------------
Are there any features you'd like to remove from C++?
Not really. People who ask this kind of question usually think of one of the
major features such as multiple inheritance, exceptions, templates, or run-time
type identification. C++ would be incomplete without those. I have reviewed
their design over the years, and together with the standards committee I have
improved some of their details, but none could be removed without doing damage.
Most of the features I dislike from a language-design perspective are part of
the C subset of C++ and couldn't be removed without doing harm to programmers
working under real-world conditions. C++'s C compatibility was a key language
design decision rather than a marketing gimmick. Compatibility has been
difficult to achieve and maintain, but real benefits to real programmers
resulted, and still result today. By now, C++ has features that allows a
programmer to refrain from using the most troublesome C features. For example,
standard library containers such as vector, list, map, and string can be used
to avoid most tricky low-level pointer manipulation.
--------------------------------------------------------------------------------
When will we have a new ARM?
Ellis&Stroustrup: The Annotated C++ Reference Manual colloquially known and
"The ARM" was written in 1989 and was the base of the C++ standards effort. It
is by now quite old and does not describe Standard C++.
Andrew Koenig and I are working on a replacement based on the actual text of
the ISO standard. This work was delayed because of difficulty in getting
permission from ISO to use the actual standards text. (I considered using any
other text disloyal to my friends and colleagues on the standards committees
and a disfavor to the C++ community). Our work on this "ARM++" has been delayed
(again), so I don't dare give an estimate of when it will become available.
--------------------------------------------------------------------------------
When will you publish a 4th edition of "The C++ Programming Language"?
There won't be a need until 2004 or so. The definition of C++ and the
fundamental techniques that it supports are unlikely to change significantly
before then. When I write, I aim for a long "shelf life" and the ISO C++
standard ensures basic stability. In this context, it is important that The C++
Programming Language (3rd Edition) describes Standard C++, its standard library,
and the techniques they support rather than some particular implementation and
some proprietary library. Minor changes and additions I deal with through
"online maintenance" and minor improvements to new printings of the book; see
my errata.
For 2000 printings - including the hardcover "special edition" - I have two new
appendices on Locales and Standard-Library Exception Safety.
--------------------------------------------------------------------------------
Should I buy the "Special Edition" of "The C++ Programming Language"?
Sure , buy it early and often :-) I expect to see it in the stores from about
mid-February.
Seriously, the difference between the special edition and printings of the 3rd
edition that will postdate it is just the hard cover (and the price difference
implied by that stronger cover).
If I were a C++ programmer and hadn't read The C++ Programming Language (3rd
Edition), I'd buy and read either the 3rd edition or the special edition. If I
used my textbooks and references heavily, I'd choose the hard cover. The cover
on the 3rd is the best soft cover available, but it doesn't equal the special
edition's hard cover.
If I already had the 3rd edition, I'd buy the SE if my current copy were
fraying or if my copy were an early printing.
Compared to the first printing, the special edition and the most recent
printings of the 3rd edition have about 1,000 corrections and clarifications.
As a heavy C++ user, I find that significant. There are also the two new
appendices (just over 100 pages; available for download: Locales and
Standard-Library Exception Safety).
Existing material has not moved around so page numbers can be used to refer to
material in old printings, new printings of the 3rd edition, and in the SE.
The SE also has an improved index.
--------------------------------------------------------------------------------
Is ``int* p;'' right or is ``int *p;'' right?
Both are "right" in the sense that both are valid C and C++ and both have
exactly the same meaning. As far as the language definitions and the compilers
are concerned we could just as well say ``int*p;'' or ``int * p;''
The choice between ``int* p;'' and ``int *p;'' is not about right and wrong,
but about style and emphasis. C emphasized expressions; declarations were often
considered little more than a necessary evil. C++, on the other hand, has a
heavy emphasis on types.
A ``typical C programmer'' writes ``int *p;'' and explains it ``*p is what is
the int'' emphasizing syntax, and may point to the C (and C++) declaration
grammar to argue for the correctness of the style. Indeed, the * binds to the
name p in the grammar.
A ``typical C++ programmer'' writes ``int* p;'' and explains it ``p is a
pointer to an int'' emphasizing type. Indeed the type of p is int*. I clearly
prefer that emphasis and see it as important for using the more advanced parts
of C++ well.
The critical confusion comes (only) when people try to declare several pointers
with a single declaration:
int* p, p1; // probable error: p1 is not an int*
Placing the * closer to the name does not make this kind of error significantly
less likely.
int *p, p1; // probable error?
Declaring one name per declaration minimizes the problem - in particularly when
we initialize the variables. People are far less likely to write
int* p = &i;
int p1 = p; // error: int initialized by int*
and if they do the compiler will complain.
Whenever something can be done in two ways, someone will be confused. Whenever
something is a matter of taste, discussions can drag on forever. Stick to one
pointer per declaration and always initialize variables and the source of
confusion disappears. See The Design and Evolution of C++ for a longer
discussion of the C declaration syntax.
--------------------------------------------------------------------------------
What C++ compiler do you recommend? Which libraries?
I don't recommend. It wouldn't be fair.
--------------------------------------------------------------------------------
Is Java the language you would have designed if you didn't have to be
compatible with C?
No. Java isn't even close. If people insist on comparing C++ and Java - as they
seem to do - I suggest they read The Design and Evolution of C++ (D&E) to see
why C++ is the way it is, and consider both languages in the light of the
design criteria I set for C++. Those criteria will obviously differ from the
criteria of Sun's Java team. Despite the syntactic similarities, C++ and Java
are very different languages. In many ways, Java seems closer to Smalltalk than
to C++.
Much of the relative simplicity of Java is - like for most new languages -
partly an illusion and partly a function of its incompleteness. As time passes,
Java will grow significantly in size and complexity. It will double or triple
in size and grow implementation-dependent extensions or libraries. That is the
way every commercially successful language has developed. Just look at any
language you consider successful on a large scale. I know of no exceptions, and
there are good reasons for this phenomenon.
(The paragraph above was written before Java1.1. I confidently predict that
Java will acquire a template-like mechanism and improved support for concrete
types. It simply has to do that to be reasonably complete. In addition, it will
also undergo many minor changes - mostly extensions. Later still (fall 1998), I
found a proposal from James Gosling for adding concrete types, operator
overloading, and support for numeric computation to Java: The Evolution of
Numerical Computing in Java and a debunking of some Java myths by W. Kahan, UC
Berkeley, One of the world's leading numerical analysts: How Java's
Floating-Point Hurts Everyone Everywhere).
I find most of the Java advertising on TV and in print inaccurate and
offensive. Denouncing all code written in languages other than Java as
"contamination" is insulting to programmers. Suggesting that all "legacy code"
should be rewritten in Java is wildly unrealistic and irresponsible. Sunsoft
and its followers seem to consider this kind of bombast necessary to fight "the
evil empire of Microsoft" but insults and hype simply drives programmers who
prefer to use a variety of programming languages into the arms of Microsoft.
Java isn't platform independent; it is a platform. Like Windows, it is a
proprietary commercial platform. That is, you can write programs for
Windows/Intel or Java/JVM, and in each case you are writing code for a platform
owned by a single corporation and tweaked for the commercial benefit of that
corporation. It has been pointed out that you can write programs in any
language for the JVM and associated operating systems facilities. However, the
JVM, etc., are heavily biased in favor of Java. It is nowhere near being a
general reasonably language-neutral VM/OS.
Personally, I'll stick to reasonably portable C++ for most of the kind of work
I think most about and use a variety of languages for the rest.
--------------------------------------------------------------------------------
Do you really recommend Ada over C++ for larger projects?
No. I have no idea who started that rumor, but it must have been an
overenthusiastic or malicious Ada devotee.
--------------------------------------------------------------------------------
Would you compare C++ to "some language"?
No, sorry, I won't. You can find the reason in the introductory notes of The
Design and Evolution of C++:
"Several reviewers asked me to compare C++ to other languages. This I have
decided against doing. Thereby, I have reaffirmed a long-standing and strongly
held view: Language comparisons are rarely meaningful and even less often fair.
A good comparison of major programming languages requires more effort than most
people are willing to spend, experience in a wide range of application areas, a
rigid maintenance of a detached and impartial point of view, and a sense of
fairness. I do not have the time, and as the designer of C++, my impartiality
would never be fully credible.
I also worry about a phenomenon I have repeatedly observed in honest attempts
at language comparisons. The authors try hard to be impartial, but are
hopelessly biased by focusing on a single application, a single style of
programming, or a single culture among programmers. Worse, when one language is
significantly better known than others, a subtle shift in perspective occurs:
Flaws in the well-known language are deemed minor and simple workarounds are
presented, whereas similar flaws in other languages are deemed fundamental.
Often, the workarounds commonly used in the less-well-known languages are
simply unknown to the people doing the comparison or deemed unsatisfactory
because they would be unworkable in the more familiar language.
Similarly, information about the well-known language tends to be completely
up-to-date, whereas for the less-known language, the authors rely on
several-year-old information. For languages that are worth comparing, a
comparison of language X as defined three years ago vs. language Y as it
appears in the latest experimental implementation is neither fair nor
informative. Thus, I restrict my comments about languages other than C++ to
generalities and to very specific comments."
That said, I consider C++ the best choice in programming language for a wide
variety of people and applications.
--------------------------------------------------------------------------------
Others do compare their languages to C++; doesn't that annoy you?
It does when it is done incompetently or for commercial gain. The most widely
circulated comparisons tend to be those written by proponents of some language,
Z, to prove that Z is better that other languages. Given its wide use, C++ is
often top of the list of languages that the proponents of Z wants to prove
inferior. Often, such papers are "published" or distributed by a company that
sells Z as part of a marketing campaign. Surprisingly, many seem to take an
unreviewed paper written by people working for a company selling Z "proving"
that Z is best seriously. One problem is that there are always grains of truth
in such comparisons. After all, no language is better than every other in all
possible ways. C++ certainly isn't perfect, but selective truth can be most
seductive and occasionally completely misleading.
When looking at a language comparison consider who wrote it, consider carefully
if the descriptions are factual and fair, and also if the comparison criteria
are themselves fair for all languages considered. This is not easy.
--------------------------------------------------------------------------------
You won't compare C++ to other languages, but you write diatribes about C++?
I don't write diatribes (that's a hostile characterization of some text), but I
do consider it reasonable - possibly even a duty - for someone who designed a
language to explain its virtues and defend it against hostile
characterizations. Often, I also point out the limitations of C++ and the
fundamental assumptions of the design of C++ (for example, see D&E).
--------------------------------------------------------------------------------
C is better than C++ for small projects, right?
Not in my opinion. I never saw a project for which C was better than C++ for
any reason but the lack of a good C++ compiler.
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Is C a subset of C++?
In the strict mathematical sense, C isn't a subset of C++. There are programs
that are valid C but not valid C++ and even a few ways of writing code that has
a different meaning in C and C++. However, C++ supports every programming
technique supported by C. Every C program can be written in essentially the
same way in C++ with the same run-time and space efficiency. It is not uncommon
to be able to convert tens of thousands of lines of ANSI C to C-style C++ in a
few hours. Thus, C++ is as much a superset of ANSI C as ANSI C is a superset of
K&R C and much as ISO C++ is a superset of C++ as it existed in 1985.
Well written C tends to be legal C++ also. For example, every example in
Kernighan & Ritchie: "The C Programming Language (2nd Edition)" is also a C++
program.
Examples of C/C++ compatibility problems:
int main()
{
double sq2 = sqrt(2); /* Not C++: call undeclared function */
int s = sizeof('a'); /* silent difference: 1 in C++ sizeof(int) in C
*/
}
Calling an undeclared function is poor style in C and illegal in C++. So is
passing arguments to a function using a declaration that doesn't list argument
types:
void f(); /* argument types not mentioned */
void g()
{
f(2); /* poor style C. Not C++ */
}
In C, a void* can be implicitly converted to any pointer type, and free-store
allocation is typically done using malloc() which has no way of checking if
"enough" memory is requested:
void* malloc(size_t);
void f(int n)
{
int* p = malloc(n*sizeof(char)); /* not C++. In C++, allocate using
`new' */
char c;
void* pv = &c;
int* pi = pv; /* implicit conversion of void* to int*. Not in C++ */
}
Note the potential alignment error caused by the implicit conversion of the
void* to a int*.
When converting from C to C++, beware that C++ has more keywords than C:
int class = 2; /* ok in C. Syntax error in C++ */
int virtual = 3; /* ok in C. Syntax error in C++ */
Except for a few examples such as the ones shown above (and listed in detail in
the C++ standard and in Appendix B of The C++ Programming Language (3rd Edition)
), C++ is a superset of C. (Appendix B is available for downloading).
--------------------------------------------------------------------------------
What is the difference between C and C++?
C++ is a direct descendant of C that retains almost all of C as a subset. C++
provides stronger type checking than C and directly supports a wider range of
programming styles than C. C++ is "a better C" in the sense that it supports
the styles of programming done using C with better type checking and more
notational support (without loss of efficiency). In the same sense, ANSI C is a
better C than K&R C. In addition, C++ supports data abstraction,
object-oriented programming, and generic programming (see The C++ Programming
Language (3rd Edition)"; Appendix B discussing compatibility issues is
available for downloading).
I have never seen a program that could be expressed better in C than in C++
(and I don't think such a program could exist - every construct in C has an
obvious C++ equivalent). However, there still exist a few environments where
the support for C++ is so weak that there is an advantage to using C instead.
For a discussion of the design of C++ including a discussion of its
relationship with C see The Design and Evolution of C++.
--------------------------------------------------------------------------------
When was C++ invented?
I started work on what became C++ in 1979. The initial version was called "C
with Classes". The first version of C++ was used internally in AT&T in August
1983. The name "C++" was used late that year. The first commercial
implementation was released October 1985 at the same time as the publication of
the 1st edition of The C++ Programming Language. Templates and exception
handling were included later in the 1980es and documented in The Annotated C++
Reference Manual and The C++ Programming Language (2rd Edition).
The current definition of C++ is The ISO C++ Standard described in The C++
Programming Language (3rd Edition).
You can find a more complete timeline and more detailed explanations in The
Design and Evolution of C++.
--------------------------------------------------------------------------------
Why did you invent C++?
I wanted to write efficient systems programs in the styles encouraged by
Simula67. To do that, I added facilities for better type checking, data
abstraction, and object-oriented programming to C. The particular projects that
prompted this work had to do with distributing operating system facilities
across a network. The more general aim was to design a language in which I
could write programs that were both efficient and elegant. Many languages force
you to choose between those two alternatives.
The specific tasks that caused me to start designing and implementing C++
(initially called "C with Classes") had to do with the design of a distributed
operating system.
You can find more detailed explanations in The Design and Evolution of C++.
--------------------------------------------------------------------------------
Why doesn't C++ have garbage collection?
If you want automatic garbage collection, there are good commercial and
public-domain garbage collectors for C++. For applications where garbage
collection is suitable, C++ is an excellent garbage collected language with a
performance that compares favorably with other garbage collected languages. See
The C++ Programming Language (3rd Edition) for a discussion of automatic
garbage collection in C++. See also, Hans-J. Boehm's site for C and C++ garbage
collection.
--------------------------------------------------------------------------------
Why is the code generated for the "Hello world" program ten times larger for
C++ than for C?
It isn't on my machine, and it shouldn't be on yours. In fact, the object code
for the C++ version of the "hello world" program is smaller than the C version
on my machine. There is no language reason why the one version should be larger
than the other. It is all an issue on how the implementor organized the
libraries. If one version is significantly larger than the other, report the
problem to the implementor of the larger.
--------------------------------------------------------------------------------
What do you think of EC++?
EC++ is an (almost) subset of C++ lacking exceptions, templates, namespaces,
RTTI support, multiple inheritance, etc. being defined by an "industry
consortium." I am not in favor of language subsets or dialects. I am especially
not fond of subsets that cannot support the standard library so that the users
of that subset must invent their own incompatible foundation libraries. I fear
that a defined subset of C++ could split the user community and cause acrimony
(3/31/1999: I just saw an advertisement that used vivid graphics to indicate
how EC++ reduced "fat" (i.e. memory space) by abolishing - among other things -
namespaces, templates, and C++ standard strings. Sigh). I strongly prefer work
on "standards" to occur in an open forum (such as ISO or a national standards
organization).
I do not think that a defined subset or dialect of C++ is necessary for
embedded systems programming (see my keynote at the Spring'99 Embedded Systems
Conference). The embedded systems programming community would be better served
by a group considering and documenting how the needs of the embedded systems
community relates to C++. Different projects and organizations would then have
a rational basis for their decisions of what part of C++ to use. The embedded
systems community is diverse. Many currently rely on templates, some are using
exceptions, and namespaces have no implications on the size or speed of
programs. Only the language and library defined by the ISO C++ standard is
flexible, general, and well-defined enough to serve the embedded systems
community for the decades to come. In the relatively few cases where run-time
space or efficiency is a problem with Standard C++ (usually because of
sub-optimal implementations) a few compiler switches can help the optimizer
(e.g. for some projects and for some compilers disabling exceptions may yield
significant performance benefits - and sometimes it will not).
--------------------------------------------------------------------------------
C++ got its Object-Oriented concepts from Smalltalk?
No. C++ got the key notions of classes, derived classes, virtual functions (in
other words, the notions of encapsulation, inheritance and polymorphism) from
Simula just like Smalltalk did. In terms of family relationships, C++ and
Smalltalk are siblings.
--------------------------------------------------------------------------------
Is C++ an Object-Oriented language?
C++ is a multi-paradigm language that supports Object-Oriented and other useful
styles of programming. If what you are looking for is something that forces you
to do things in exactly one way, C++ isn't it. There is no one right way to
write every program - and even if there were there would be no way of forcing
programmers to use it.
That said, writing C-style programs in C++ is for most applications not an
optimal use of C++. To be a really effective C++ programmer, you must use the
abstraction mechanisms and the type system in a way that fits reasonably with
their intent. Trying to ignore or defeat the C++ type system is a most
frustrating experience.
Writing Smalltalk-style in C++ can be equally frustrating and sub-optimal as
writing C-style code in C++.
--------------------------------------------------------------------------------
Did you really say that?
Yes, I did say something along the lines of "C makes it easy to shoot yourself
in the foot; C++ makes it harder, but when you do it blows your whole leg off."
What people tend to miss, is that what I said there about C++ is to varying
extent true for all powerful languages. As you protect people from simple
dangers, they get themselves into new and less obvious problems. Someone who
avoids the simple problems may simply be heading for a not-so-simple one. One
problem with very supporting and protective environments is that the hard
problems may be discovered too late or be too hard to remedy once discovered.
Also, a rare problem is harder to find than a frequent one because you don't
suspect it.
--------------------------------------------------------------------------------
Did you really give an interview to IEEE?
in which you confessed that C++ was deliberately created as an awful language
for writing unmaintainable code to increase programmers' salaries?
Of course not. Read the real IEEE interview.
--------------------------------------------------------------------------------
Why is the language called C++?
For the first few years, I called my language ``C with Classes.'' However
people had taken to calling C with Classes ``new C,'' and then C. This
abbreviation led to C being called ``plain C,'' ``straight C,'' and ``old C.''
The last name, in particular, was considered insulting, so common courtesy and
a desire to avoid confusion led me to look for a new name. I picked C++ because
it was short, had nice interpretations, and wasn't of the form ``adjective C.''
In C, ++ can, depending on context, be read as ``next,'' ``successor,'' or
``increment,'' though it is always pronounced ``plus plus.'' The name C++ and
its runner up ++C are fertile sources for jokes and puns - a
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