Question

Mark the following statements as true or false. a. \(A\) function that changes the value of a reference parameter also changes the value of the actual parameter. b. \(A\) variable name cannot be passed to a value parameter. c. If a \(C++\) function does not use parameters, parentheses around the empty parameter list are still required. d. In \(C++,\) the names of the corresponding formal and actual parameters must be the same. e. Whenever the value of a reference parameter changes, the value of the actual parameter changes. f. In \(C++,\) function definitions can be nested; that is, the definition of one function can be enclosed in the body of another function. g. Using global variables in a program is a better programming style than using local variables, because extra variables can be avoided. h. In a program, global constants are as dangerous as global variables. i. The memory for a static variable remains allocated between function calls.

Short answer

a: True, b: False, c: True, d: False, e: True, f: False, g: False, h: False, i: True.

Step-by-step solution

Evaluate Statement a

Statement a is true. If a reference parameter in a function is used, it means that the function can modify the actual variable passed to the function because both the reference and the actual variable point to the same memory location.

Evaluate Statement b

Statement b is false. A variable name can be passed to a value parameter. When a variable is passed as an argument to a value parameter, the function receives a copy of the variable's value, but the actual variable is not affected.

Evaluate Statement c

Statement c is true. In C++, even if functions do not take parameters, parentheses are still required in the function declaration and definition to indicate an empty parameter list.

Evaluate Statement d

Statement d is false. In C++, the names of the formal parameters (in the function definition) and the actual parameters (in the function call) do not need to be the same; only their corresponding data types need to match.

Evaluate Statement e

Statement e is true. When the value of a reference parameter changes, it directly modifies the value of the actual parameter since they refer to the same address in memory.

Evaluate Statement f

Statement f is false. C++ does not allow function definitions to be nested. Each function must be defined independently.

Evaluate Statement g

Statement g is false. Using global variables generally breaks encapsulation and can make a program harder to understand and maintain. Local variables are preferred for maintaining clear scope and avoiding side effects.

Evaluate Statement h

Statement h is false. Global constants do not change, so they do not introduce the same risks as global mutable variables. Global constants are generally considered safe, as they can help avoid magic numbers and improve code readability.

Evaluate Statement i

Statement i is true. In C++, memory for a static variable remains allocated between function calls, and it retains its value even after the function exits.

Key concepts

Reference Parameters

In C++, reference parameters allow functions to modify the value of the variables passed to them. This occurs because reference parameters work by creating an alias, or reference, to the actual variable's memory location instead of a copy of the variable's value. Thus, changes made to the reference parameter inside the function also affect the original variable.

This concept is useful when a function needs to change the input data directly. Developers use the ampersand `&` symbol in the function parameter list to denote a reference, such as `void modifyValue(int ¶m)`. This makes it very efficient for functions to manipulate large data structures without unnecessary copying.

• Reference parameters provide direct access.
• They eliminate the need for return statements for altering multiple values.

It’s important for programmers to be cautious as changing values via reference can lead to unexpected results if not properly managed.

Global vs Local Variables

Understanding the difference between global and local variables is fundamental in C++ programming. Global variables are defined outside any function and are accessible from any point within the program. They are usually declared at the beginning of a program’s code.

Conversely, local variables are declared within a function or block, and their scope is limited to that function or block. These variables cannot be accessed outside their defining scope, which promotes encapsulation and helps avoid potential naming conflicts.

Using local variables is often preferable because it keeps data tightly bound to the functions that use it. This also minimizes unintended side effects since these variables can only be altered within a very specific part of the code.

• Global variables increase risk of accidental modifications.
• Local variables improve modularity and function independence.

While global variables can make some tasks easier, their overuse can lead to code that is difficult to debug and maintain.

Function Definitions in C++

Function definitions in C++ set the blueprint for executing specific tasks when the function is called. Each function needs a specific syntax, typically including a return type, function name, and parentheses for parameters—even if no parameters are present.

This structure ensures that functions are organized clearly, separating implementation from the rest of the code. Unlike some languages that allow nested functions, C++ requires that each function stand independently.

Functions can be defined inside classes when using Object-Oriented Programming, but outside of functions in procedural code. The separation of function definitions enhances readability and enables easier debugging and upgrading of programs.

• Proper function syntax includes return type and parameter list.
• Define functions independently to maintain clear code structure.

This clear structure aids in developing scalable software that is easy to navigate for multiple programmers.

Static Variables in C++

Static variables in C++ retain their value between function calls. These variables are declared with the `static` keyword within a function, providing a way to preserve state across function invocations without resorting to global variables.

A static variable’s lifetime extends for the duration of the program, but its scope remains local to the function in which it is declared. This means that on subsequent calls to the function, the static variable retains its last modified value rather than being reinitialized.

Static variables are particularly useful when a function needs to remember information between calls, such as counting how many times a function is invoked or storing interim results.

• Static variables maintain state between function calls.
• They provide a middle ground between local and global variables.

However, they should be used judiciously to avoid maintenance issues, as excessive use can lead to difficult-to-track code behavior.