Which symbol should be used to pass the object by reference in C++?

Question

Accepted Answer

The correct option is (1):
In C++, the ampersand symbol (&) is the specific and correct symbol used in a function's parameter list to declare a variable as a **reference**. This mechanism is known as "pass by reference." When you pass an object to a function by reference (e.g., `void func(ClassName& obj)`), you are not creating a duplicate copy of the object; instead, the parameter `obj` becomes a direct **alias** for the original object in the calling function's memory. This approach is highly efficient, particularly for large objects like user-defined classes, because it avoids the overhead of copying vast amounts of data. Furthermore, using a reference allows the called function to directly modify the data of the original object, which is one of the primary reasons for choosing pass by reference over pass by value.

The incorrect option is (2):
The @ symbol, often called the "at sign," is not a standard or reserved operator in the C++ programming language. C++ has a strict syntax where every operator and symbol has a defined purpose, such as arithmetic, relational, or logical operations. The @ symbol is not part of the core language specification for declaring types, pointers, or references. If you were to use the @ symbol in a function signature to try to pass an object by reference, the C++ compiler would generate a syntax error, as it does not recognize this symbol for this purpose.

The incorrect option is (3):
The dollar sign ($) is also not a recognized operator, keyword, or type modifier in the standard C++ language. In programming, symbols like $ often have specific meaning in other languages, such as indicating a variable in PHP or a string literal in some shell scripts. However, in the C++ syntax, $ has no role in defining the control flow or data types. Attempting to use the $ symbol to declare a reference parameter in a C++ function would immediately lead to a compilation failure because the symbol is simply not defined for the purpose of creating an alias or reference type.

The incorrect option is (4):
The option "None of the above" is incorrect because the correct symbol for implementing "pass by reference" in C++ is indeed provided as Option 1, which is the ampersand (&). Since the ampersand is a core, fundamental feature of C++ specifically designed for declaring references (aliases) to objects and variables in function parameters, there is a definitively correct option available. Therefore, you must select the ampersand as the valid C++ symbol for this operation.