What is the '\' operator in the C language?

Question

The example that I am looking at is like this:

#define CONTROL_MEM_SIZE    ((CONTROL_ITEM_SIZE * CONTROL_QUEUE_SIZE) +   \\
                            portQ         


        

Answer 1

C11 p5.1.1.2: Translation phase 2

Each instance of a backslash character (\) immediately followed by a new-line character is deleted, splicing physical source lines to form logical source lines. [...]