Several versions of the compiler (C, C++, Objective-C, Ada, Fortran, and Java) are integrated; this is why we use the name "GNU Compiler Collection". GCC can compile programs written in any of these languages. The Ada, Fortran, and Java compilers are described in separate manuals.
"GCC" is a common shorthand term for the GNU Compiler Collection. This is both the most general name for the compiler, and the name used when the emphasis is on compiling C programs (as the abbreviation formerly stood for "GNU C Compiler").
When referring to C++ compilation, it is usual to call the compiler "G++". Since there is only one compiler, it is also accurate to call it "GCC" no matter what the language context; however, the term "G++" is more useful when the emphasis is on compiling C++ programs.
Similarly, when we talk about Ada compilation, we usually call the compiler "GNAT", for the same reasons.
We use the name "GCC" to refer to the compilation system as a whole, and more specifically to the language-independent part of the compiler. For example, we refer to the optimization options as affecting the behavior of "GCC" or sometimes just "the compiler".
Front ends for other languages, such as Mercury and Pascal exist but have not yet been integrated into GCC. These front ends, like that for C++, are built in subdirectories of GCC and link to it. The result is an integrated compiler that can compile programs written in C, C++, Objective-C, or any of the languages for which you have installed front ends.
In this manual, we only discuss the options for the C, Objective-C, and C++ compilers and those of the GCC core. Consult the documentation of the other front ends for the options to use when compiling programs written in other languages.
G++ is a compiler, not merely a preprocessor. G++ builds object code directly from your C++ program source. There is no intermediate C version of the program. (By contrast, for example, some other implementations use a program that generates a C program from your C++ source.) Avoiding an intermediate C representation of the program means that you get better object code, and better debugging information. The GNU debugger, GDB, works with this information in the object code to give you comprehensive C++ source-level editing capabilities (see C and C++).