How Ampersand (&) Works in C

Understanding the Ampersand Operator

The & operator in C serves multiple purposes, including:

• Taking the address of a variable: &x returns the memory address of variable x.
• Passing arguments by reference: void foo(CDummy& x); passes variable x to function foo by reference, allowing modifications made inside foo to be reflected in the original variable.
• Declaring reference variables: int& r = k; creates a reference variable r that aliases an existing variable k. Any changes made to r will directly affect k.

In the Context of the Provided Code

The code snippet you provided demonstrates the use of ampersand to check for equality between a pointer (b) and a reference variable (a). This comparison is valid because a reference is implicitly converted to a pointer when needed. The & operator on the left-hand side of &param == this is unnecessary and confusing. The correct comparison is simply param == this.

In short, the & operator in C provides a versatile way to work with variables by allowing you to access their memory addresses, pass them by reference, and create reference variables that alias existing variables.