C Problems in linux Eclipse

[vakhoQ]

I have Ubuntu Linux. I have just writen programm in C by Eclipse C++ but it does not work in Linux. And it works in Windows.

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
float a,b;
a=49;
b= sqrt(a);
printf("%f", b);
}

There is error:

make all 
Building target: Program_Name
Invoking: GCC C Linker
gcc  -o"Program_Nam"  ./src/Program_Nam.o   
./src/Program_Nam.o: In function `main':
/home/koro/Documents/C/Program_Nam/Debug/../src/Program_Nam.c:17: undefined reference to `sqrt'
collect2: ld returned 1 exit status
make: *** [Program_Nam] Error 1

I also make the same in Windows Dev C++ and there works. Linux have probblems with this code: b= sqrt(a);

do you Know why and what can I do?



Also I can run this proggram with terminal by gcc. For example:

gcc code.c -o  code
./code

if I add "-lm" to this code program will work. For exaple:

gcc code.c -o  code -lm

I wont to know why is imposible to run the program without -lm? why is -lm important? what is -lm and -o?

And how can I run the program in Eclipse C++ in linux. Because Eclipse is more comfortable than Terminal and notepad. it's comportable like Dev C++.

[gerard4143]

Using the -lm switch tells the compiler to include the math library.

[vakhoQ]

1) And what is -o? why can't link my program to the math library? I have writen in the code #include <math.h>

2) And how can I compile my program in Eclipse C++? The program automaticly debugs my code. I dont use Termingal here.

Thanks a lot

[gerard4143]

1) And what is -o? why can't link my program to the math library? I have writen in the code #include <math.h>

2) And how can I compile my program in Eclipse C++? The program automaticly debugs my code. I dont use Termingal here.

Thanks a lot

The -o switch tells the compiler that the following name is the name of the executable...

Including <math.h> is just pasting the contents of the math.h header file into the said file. Using the -lm informs the compiler to use the math 'library' for name/label resolution..

Question two? I never used Eclipse C++ so I don't know...