static global variable, global variable

A static global variable is local to the translation unit it is defined in. So, if you define static int a; in two different translation units, this will create two independent variables. If you define a non-static global variable int b; in two translation units, you will experience a linker error (but you can use extern int b; in one of the two translation units to tell the linker that it should use the global variable from the other translation unit).

 

A source file toghether with all the headers and source files included via the preprocessing directive #include less any source line skipped by any of the conditional inclusion preprocessing directives is called a translation unit.

 

A "translation unit" is a source file plus any headers or other source files it #includes, plus any files that THEY include, and so on. A source file is just that...one source file.

 

A translation unit is the basic unit of compilation in C++. It contains:

• all the contents of a single source file after the preprocessor has run its course
• the contents of any header files directly or indirectly included by it
• minus any lines ignored using conditional preprocessing statements

A single translation unit gets compiled into an object file, library, or executable program.

A source file, by contrast, is a stand-alone file, just like any other file on your file system. Once compiled, it can be a component of a translation unit as mentioned above.