What is the role of the part of the compiler that pre-reads the program text called?

The part of the compiler that pre-reads the program text is known as the preprocessor. Its primary role is to handle directives that are prefixed by the '#' symbol, such as including headers and defining macros. The preprocessor processes these directives before the actual compilation begins, effectively preparing the source code for the next stages of compilation.

For instance, when a program includes a header file, the preprocessor replaces the relevant line in the source code with the contents of that header file. This allows programmers to organize code into multiple files and manage dependencies effectively. The preprocessor also evaluates conditional compilation directives, enabling different code segments to be compiled based on defined conditions. This functionality is essential in modular programming and can help improve code maintainability.

In contrast, the linker is responsible for linking object files into a final executable, while the interpreter executes code directly without producing intermediate object files. The compiler driver orchestrates the overall compilation process but does not pre-read the program text itself. Therefore, the preprocessor is crucial for the initial handling and organization of the program's source code prior to compilation.