The stringize or hash symbol (#) can be used in a macro definition to convert the macro parameter into a string constant. You can imagine that the parameter is enclosed in double quotes and returned. It is also known as a token-concatenation operator.
The token-pasting operator (##) combines two parameters when used in a macro definition. That is, the two parameters on either side of each ## operator are joined into a single string. More precisely, it performs string concatenation on the two parameters to form a new string.
In this recipe, we will learn how to apply stringize and token-pasting operators in computing. The user is asked to specify a certain pizza size and their desired toppings and, accordingly, the price of the pizza is displayed.