Compile the hello World C language program in Linux

I used it like this. Program
# Include <iostream. h>
Int main (void)
{
Int I, J;
J = 0;
I = J + 1;
Cout <"Hello world! "<Endl;
Cout <"The result is" <I <Endl;
Return 0;
}
Use G ++-O test. cpp. However, there is an error in this case, prompting that iostream. h cannot be opened and modified to such a program.
# Include <iostream>
Using namespace STD;
Int main (void)
{
Int I, J;
J = 0;
I = J + 1;
Cout <"Hello world! "<Endl;
Cout <"The result is" <I <Endl;
Return 0;
}
The running result of G ++-O test. cpp is correct.
<Iostream> and <iostream. h> It is different. The former has no suffix. In fact, you can see in your compiler include folder that the two are two files. When you open the file, you will find that Code Is different.
Suffix. h header file C ++ standards have been explicitly proposed not to support, earlier implementation of the standard library function defined in the global space, declared in the. in the header file with the suffix H, the C ++ standard is used to distinguish it from C, and to correctly use the namespace, it is required that the header file does not use the suffix. h.
Therefore, when <iostream. h> when <iostream> is used, it is equivalent to calling the library function in C and using a global namespace, that is, the early C ++ implementation, the header file does not define a global namespace. You must use namespace STD; To use cout correctly.
Secondly, when programming in Linux, the C ++ program can save in the format of. CC. C. cpp ......