Description of preprocessing and its connection with symbol table manager?

Answer 1

Preprocessing is processing before the main processing.

In php (php: hypertext preprocessor) the web server goes through the page and executes the php to generate the HTML page you're about to see. When your web browser processes the web page with it's layout engine, to give you what you see from all that confusing HTML, that's the main processing.

e.g. <?php echo "Hello World!"?> outputs 'Hello World!' into the HTML document before it's sent.

In programming on source code the preprocessor does about the same thing. It goes through and look for all the preprocessor instructions and executes them on the file. The main processing would be actually compiling the source code.

e.g. #define ADOLLAR "$1.00" causes the preprocessor to go through the document and replace all occurrences of ADOLLAR with "$1.00".

A table manager is basically a dictionary for the compiler/preprocessor, it holds the symbols and their associated definitions. The preprocessor would go through the document and add the "#DEFINE"s and their values to the symbol table. So after the example above it would look like:

ADOLLAR | "$1.00"

and the preprocessor would look through the rest of the document looking up all the symbols in the table until it found 'ADOLLAR' then replace it with "$1.00".