The error is clear: the iostream header file, which is part of standard library, is not in any of the directories that the compiler is looking from. Being standard heaser, it should be included as part of the compiler installation. Either the installation or configuration has errors (or the compiler version is too old to include that header).
1. Make sure the name of the file ends with the extension .cpp , not .c
The compiler usually auto detects whether to use a c or c++ compiler depending on the file type. Since you are writing C++ code, you need a C++ compiler, therefore name the file "something.cpp".