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can u say me how to write a simple C program to find the square root a no


First you do realise you asking a C++ expert about C programming don't you?

In this case however the differences to the answer are minimal.

1/ Include <math.h> (<cmath> for C++) to include the required function declaration(s).

2/ Call the sqrt function passing it the value you wish to find the square root for. The returned value from sqrt is the positive square root of the value passed in.

The pre-C99 version of the C language standard only supports a sqrt function that takes and returns double values.

C99 adds sqrtf and sqrtl that take and return float and long double values respectively.

C++ supports function overloading on parameter type and number, and adds float and long double overloads of sqrt (no d or l suffix required).

Note that passing a negative number to a sqrt function is considered a domain error. In such cases an implementation defined value is returned and errno may be set to a value of EDOM (this is no longer required by C99 as an optimisation).


     double square_root_10 = sqrt(10.0);  


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Ralph McArdell


I am a software developer with more than 15 years C++ experience and over 25 years experience developing a wide variety of applications for Windows NT/2000/XP, UNIX, Linux and other platforms. I can help with basic to advanced C++, C (although I do not write just-C much if at all these days so maybe ask in the C section about purely C matters), software development and many platform specific and system development problems.


My career started in the mid 1980s working as a batch process operator for the now defunct Inner London Education Authority, working on Prime mini computers. I then moved into the role of Programmer / Analyst, also on the Primes, then into technical support and finally into the micro computing section, using a variety of 16 and 8 bit machines. Following the demise of the ILEA I worked for a small company, now gone, called Hodos. I worked on a part task train simulator using C and the Intel DVI (Digital Video Interactive) - the hardware based predecessor to Indeo. Other projects included a CGI based train simulator (different goals to the first), and various other projects in C and Visual Basic (er, version 1 that is). When Hodos went into receivership I went freelance and finally managed to start working in C++. I initially had contracts working on train simulators (surprise) and multimedia - I worked on many of the Dorling Kindersley CD-ROM titles and wrote the screensaver games for the Wallace and Gromit Cracking Animator CD. My more recent contracts have been more traditionally IT based, working predominately in C++ on MS Windows NT, 2000. XP, Linux and UN*X. These projects have had wide ranging additional skill sets including system analysis and design, databases and SQL in various guises, C#, client server and remoting, cross porting applications between platforms and various client development processes. I have an interest in the development of the C++ core language and libraries and try to keep up with at least some of the papers on the ISO C++ Standard Committee site at


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