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Since array references decay into pointers ...
Since array references decay into pointers, if arr is an array, what's the difference between arr and &arr? The type. In Standard C, &arr yields a pointer, of type pointer-to-array-of-T, to the entire array. (In pre-ANSI C, the & in &arr generally elicited a warning, and was generall... 2015-12-09, 1663👍, 0💬

Wy compiler is rejecting the simplest possible test programs ...
My compiler is rejecting the simplest possible test programs, with all kinds of syntax errors. It's complaining about the first line of main(int argc, char **argv) { return 0; } Perhaps it is a pre-ANSI compiler, unable to accept function prototypes and the like. If you don't have access to an ANSI ... 2015-12-02, 1662👍, 0💬

What does the message Automatic aggregate intialization is an ANSI feature mean?
What does the message Automatic aggregate intialization is an ANSI feature'' mean? My compiler is complaining about valid ANSI code. Messages like these are typically emitted by pre-ANSI compilers which have been upgraded just enough to detect (but not properly translate) new C features which were i... 2015-11-30, 1660👍, 0💬

Here is a good puzzle: how do you write a program which produces its own source code as output?
Here is a good puzzle: how do you write a program which produces its own source code as output? It is actually quite difficult to write a self-reproducing program that is truly portable, due particularly to quoting and character set difficulties. Here is a classic example (which ought to be presente... 2015-01-02, 1659👍, 0💬

What is the use of trace utility?
What is the use of trace utility? Tracing is a very important monitoring and debugging tool for distributed, multitier applications. Such applications often contain problems that can only be observed when the application is under a heavy load and the inherent randomness of a real-life environment. T... 2014-11-10, 1658👍, 0💬

How can I open files mentioned on the command line, and parse option flags?
How can I open files mentioned on the command line, and parse option flags? Here is a skeleton which implements a traditional Unix-style argv parse, handling option flags beginning with -, and optional filenames. (The two flags accepted by this example are -a and -b; -b takes an argument.) #include ... 2015-03-11, 1656👍, 0💬

How do I send escape sequences to control a terminal or other device?
How do I send escape sequences to control a terminal or other device? If you can figure out how to send characters to the device at all , it's easy enough to send escape sequences. In ASCII, the ESC code is 033 (27 decimal), so code like fprintf(ofd, "\033[J"); sends the sequence ESC [ J . Some prog... 2015-04-20, 1655👍, 0💬

Why does the declaration extern int .....
Why does the declaration extern int f(struct x *p); give me an obscure warning message about ``struct x declared inside parameter list''? In a quirk of C's normal block scoping rules, a structure declared (or even mentioned) for the first time within a prototype cannot be compatible with other struc... 2016-01-11, 1654👍, 0💬

What is wrong with this code?
What's wrong with this code? char c; while((c = getchar()) != EOF) ... For one thing, the variable to hold getchar's return value must be an int. EOF is an ``out of band'' return value from getchar: it is distinct from all possible char values which getchar can return. (On modern systems, it does no... 2015-11-16, 1654👍, 0💬

Can I declare main as void, to shut off these annoying ....
Can I declare main as void, to shut off these annoying ``main returns no value'' messages? No. main must be declared as returning an int, and as taking either zero or two arguments, of the appropriate types. If you're calling exit() but still getting warnings, you may have to insert a redundant retu... 2015-12-20, 1652👍, 0💬

Why doesnt long int work?
Why doesn't long int n = 123456; printf("%d\n", n); work? Whenever you print long ints you must use the l (lower case letter ``ell'') modifier in the printf format (e.g. %ld). printf can't know the types of the arguments which you've passed to it, so you must let it know by using the correct format ... 2015-11-09, 1652👍, 0💬

I am trying to sort an array of strings with qsort, using strcmp as the comparison function, but it is not working.
I am trying to sort an array of strings with qsort, using strcmp as the comparison function, but it is not working. By ``array of strings'' you probably mean ``array of pointers to char.'' The arguments to qsort's comparison function are pointers to the objects being sorted, in this case, pointers t... 2015-08-12, 1651👍, 0💬

What printf format should I use for a typedef like size_t when I don't know whether it is long or some other type?
What printf format should I use for a typedef like size_t when I don't know whether it is long or some other type? Use a cast to convert the value to a known, conservatively-sized type, then use the printf format matching that type. For example, to print the size of a type, you might use printf("%lu... 2015-11-04, 1650👍, 0💬

Which of the following is the C# escape character for Null?
Which of the following is the C# escape character for Null? Which of the following is the C# escape character for Null? * \n * \0 * \f * \v \0 2014-08-06, 1650👍, 0💬

Is exit status truly equivalent to returning the same status from main?
Is exit status truly equivalent to returning the same status from main? Yes and no. The Standard says that a return from the initial call to main is equivalent to calling exit. However, a return from main cannot be expected to work if data local to main might be needed during cleanup;A few very old,... 2015-12-16, 1649👍, 0💬

What is the difference between memcpy and memmove?
What is the difference between memcpy and memmove? memmove offers guaranteed behavior if the memory regions pointed to by the source and destination arguments overlap. memcpy makes no such guarantee, and may therefore be more efficiently implementable. When in doubt, it's safer to use memmove. It se... 2015-12-07, 1649👍, 0💬

I am trying to do some simple trig...
I'm trying to do some simple trig, and I am #including &lt;math.h>, but the linker keeps complaining that functions like sin and cos are undefined. Make sure you're actually linking with the math library. For instance, due to a longstanding bug in Unix and Linux systems, you usually need to use ... 2015-07-01, 1647👍, 0💬

I am sure I've got the trig functions declared correctly, but they are still giving me wrong answers.
I am sure I've got the trig functions declared correctly, but they are still giving me wrong answers. You weren't handing them angles in degrees, were you? C's trig functions (like FORTRAN's and most other languages) accept angles in radians. The conversion from degrees to radians is simple enough: ... 2015-06-29, 1647👍, 0💬

What is C language?
What is C language? The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating system. It has since spread to many other operating systems, and is one of the most widely used programming languages. C... 2014-12-31, 1647👍, 0💬

Can I use an ifdef in a #define line ...
Can I use an #ifdef in a #define line, to define something two different ways, like this? #define a b \ #ifdef whatever c d #else e f g #endif No. You can't ``run the preprocessor on itself,'' so to speak. What you can do is use one of two completely separate #define lines, depending on the #ifdef s... 2016-02-03, 1646👍, 0💬

How can I determine whether a machines byte order is big-endian or little-endian?
How can I determine whether a machines byte order is big-endian or little-endian? The usual techniques are to use a pointer: int x = 1; if(*(char *)&amp;x == 1) printf("little-endian\n"); else printf("big-endian\n"); or a union: union { int i; char c[sizeof(int)]; } x; x.i = 1; if(x.c[0] == 1) p... 2015-02-16, 1644👍, 0💬

What does it really mean for a program to be legal or `valid or ``conforming?
What does it really mean for a program to be legal or `valid or ``conforming? Simply stated, the Standard talks about three kinds of conformance: conforming programs, strictly conforming programs, and conforming implementations. A conforming program is one that is accepted by a conforming implementa... 2015-11-23, 1643👍, 0💬

How can I tell how much destination buffer space ...
How can I tell how much destination buffer space I'll need for an arbitrary sprintf call? How can I avoid overflowing the destination buffer with sprintf? When the format string being used with sprintf is known and relatively simple, you can sometimes predict a buffer size in an ad-hoc way. If the f... 2015-10-19, 1641👍, 0💬

How can I include expansions of the macros .....
How can I include expansions of the __FILE__ and __LINE__ macros in a general-purpose debugging macro? One solution involves writing your debug macro in terms of a varargs function , and an auxiliary function which stashes the values of __FILE__ and __LINE__ away in static variables, as in: #include... 2016-01-15, 1638👍, 0💬

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.NET C C++ CSS DBA General HTML Java JavaScript JSP JUnit MySQL Networking Oracle Perl Perl PHP PL/SQL RSS Software QA SQL Server Struts Unix Windows XHTML XML