Call By Value And Call By Reference In C Mcq Exercise 2

✅ Passing a copy of the value of the variable.
✅ Passing a reference to the variable.
✅ None of the above.

Explanation:

The accurate choice is alternative (b). In C, the "Call by Value" approach involves passing a duplicate of the value of the actual parameter to the function being called. This implies that the function obtains a distinct copy of the argument, which is stored in a different memory location compared to the original variable. Consequently, any changes made to the parameter inside the function do not impact the value of the original variable in the calling function.

This behavior is particularly useful for maintaining data integrity because it prevents unintended side effects on the original data. Thus, "Call by Value" enhances predictability and reliability in C programming by ensuring that functions operate on copies rather than the actual data, thereby safeguarding the original values from accidental modifications.

What exactly takes place regarding the original variable whenever "Call by Reference" is used when passing it to a function?

✅ The original variable remains unchanged.
✅ The original variable is modified if the function modifies the parameter.
✅ A copy of the variable is modified.
✅ The variable is passed by value.

Explanation:

Option (b) is the accurate choice. The initial variable gets altered when the function makes changes to the parameter.

When a variable is passed to a function using "Call by Reference" in C, the function obtains a reference to the real variable instead of a duplicate of its value. This reference is usually achieved through pointers. Consequently, any changes made to the parameter inside the function impact the original variable in the calling function immediately. This occurs because the function works with the variable's address, enabling it to reach and modify the variable's genuine memory position.

Consequently, changes made inside the function are reflected outside the function as well, which means that the original variable's value is modified. This mechanism is useful in scenarios where the function needs to update or manipulate the actual data, such as in cases of swapping values, updating records, or modifying large data structures efficiently.

Which of the following is a correct way to implement "Call by Reference" in C?

✅ Using pointers.
✅ Using arrays.
✅ Using structures.
✅ All of the above.

Explanation:

The correct answer is option (d). The comprehensive answer is d) All of the above. Regarding C programming, "Call by Reference" can potentially be implemented successfully by using pointers, arrays, and structures, rendering answers a), b), and c) all valid. This adaptability results from the fact that each of the methods let an operation operate on and alter the original data instead of a replica. By employing pointers, an algorithm can directly manipulate a variable's value through referring to since it obtains the variable's physical address. Although an array's first element's address is passed to a function when an array is passed to it, the function receiving the address can immediately customize the array elements, reflecting changes in the original array. This is why arrays enable "Call by Reference" by default.

In C programming, which of the following is an example of "Call by Reference"?

✅ void swap (int a, int b) {int temp = a; a = b; b = temp;}
✅ void increment (int x) {(x)++; }
✅ int multiply (int x, int y) {return x * y; }
✅ void divide (float a, float b) {a = a / *b; }

Explanation:

The correct answer is option (b). In option B, the function increment takes a pointer to an integer (int x) as its parameter. This is an example of "Call by Reference" because changes made to x inside the function will affect the original variable passed as an argument. Options A, C, and D are examples of "Call by Value" because they operate on copies of the original variables (a, b, x, y, a, b), and any modifications inside the functions do not reflect in the original variables.

Which of the following statements about "Call by Reference" in C is true?

✅ It always results in faster program execution compared to "Call by Value".
✅ It allows the function to modify the actual parameters passed to it.
✅ It is implemented by passing pointers to the actual parameters as arguments.
✅ It is not supported in C programming.

Explanation:

The correct answer is option (b). It allows the function to modify the actual parameters passed to it. It allows the function to modify the original variables passed as arguments. Option A is not necessarily true; the speed difference depends on various factors and optimizations. Option C describes the mechanism of "Call by Reference" correctly. Option D is incorrect; "Call by Reference" is indeed supported in C through pointers.

What is a potential disadvantage of using "Call by Reference" in C?

✅ Inability to modify the original variables inside the function.
✅ Slower program execution compared to "Call by Value".
✅ Increased risk of pointer-related errors.
✅ Requires more memory than "Call by Value".

Explanation:

The accurate choice is alternative (c). Employing "Call by Reference" entails transmitting pointers, heightening the possibility of pointer-related issues like dereferencing null pointers or accessing memory out of bounds. Options A, C, and D do not represent drawbacks of "Call by Reference". It enables the alteration of initial variables, can match or surpass "Call by Value" in speed based on the circumstance, and does not always demand additional memory.

In Call by Reference in C, which symbol signifies passing the variable's address to a function?

Explanation:

The accurate choice is alternative (a). Within the C programming language, the & symbol signifies the location of a variable. As a prefix to a variable identifier, it specifies the specific memory address where the variable is held.

Examine the subsequent function in the C programming language:

Example


void swap(int *a, int *b) {
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}

Which calling method ensures that the values of variables are swapped?

✅ swap(a, b);
✅ swap(&a, &b);
✅ swap(a, b);
✅ swap(&a, &b);

Explanation:

The accurate choice is alternative (b). The swap function is created to interchange the values of two variables by leveraging pointers. In order to pass variables by reference (i.e., by passing their memory addresses), the appropriate method involves using the & operator preceding the variable names during the function call.

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