Question

1. What are the contents of the numbers array at the end of this code?

int numbers[] = { 35, 57, 78, 66, 41, 12 };

int *ptrA = numbers + 3;

int x = 15;

*ptrA = x++;

2.

Which of the following expressions is the correct way of dynamically allocating memory for a struct named MyStruct?

		MyStruct *m = malloc( sizeof( MyStruct ) );
		MyStruct m = (MyStruct) malloc( MyStruct );
		MyStruct *m = (MyStruct *) malloc( MyStruct );
		MyStruct *m = (MyStruct *) malloc( sizeof( MyStruct ) );

Answer 1

Question 1:
contents of the numbers array at the end of this code is
{ 35, 57, 78, 15, 41, 12 }

Question 2:
expressions is the correct way of dynamically allocating memory for a struct named MyStruct is
MyStruct *m = (MyStruct *) malloc( sizeof( MyStruct ) );

​​​​​​​

Answer 2

1. What are the contents of the numbers array at the end of this code?

Code:

C++

int numbers[] = { 35, 57, 78, 66, 41, 12 };
int *ptrA = numbers + 3;
int x = 15;
*ptrA = x++;

Explanation:

1. int numbers[] = { 35, 57, 78, 66, 41, 12 };

• This line declares an integer array named numbers and initializes it with the given values.

2. int *ptrA = numbers + 3;

• numbers[0] = 35

• numbers[1] = 57

• numbers[2] = 78

• numbers[3] = 66

• numbers[4] = 41

• numbers[5] = 12

• This line declares an integer pointer ptrA and initializes it to point to the element at index 3 of the numbers array.

• In the numbers array, the elements are:

• Therefore, ptrA points to the element 66.

3. int x = 15;

• This line declares an integer variable x and initializes it to 15.

4. *ptrA = x++;

• x++ is a post-increment operation. It means the current value of x (which is 15) is used in the expression, and then x is incremented.

• *ptrA refers to the value at the memory location pointed to by ptrA. Since ptrA points to numbers[3], *ptrA is equivalent to numbers[3].

• So, *ptrA = x++ assigns the current value of x (15) to numbers[3], and then x is incremented to 16.

• This is the crucial line. Let's break it down:

Result:

After the execution of the code, the numbers array will be:

numbers[] = { 35, 57, 78, 15, 41, 12 };

Answer:

The contents of the numbers array at the end of the code are: { 35, 57, 78, 15, 41, 12 }

2. Which of the following expressions is the correct way of dynamically allocating memory for a struct named MyStruct?

Let's analyze each option:

• MyStruct *m = malloc( sizeof(MyStruct) );

• This is the correct way.

• malloc allocates memory in bytes. sizeof(MyStruct) gives the size of the MyStruct structure in bytes.

• The result of malloc is a pointer to the allocated memory, which is then cast to MyStruct* and assigned to the pointer m.

• MyStruct m = (MyStruct) malloc( MyStruct );

• This is incorrect.

• malloc expects a size in bytes, not the structure type itself.

• The assignment is also incorrect as m is declared as a MyStruct (not a pointer), but malloc returns a pointer.

• MyStruct *m = (MyStruct *) malloc( MyStruct );

• This is incorrect for the same reason as the previous option. malloc expects a size in bytes.

• MyStruct *m = (MyStruct *) malloc( sizeof(MyStruct) );

• This is also correct. It's essentially the same as the first option, just with an explicit cast to MyStruct*. While the cast is not strictly necessary in C, it's often used in C++ for clarity and type safety.

Answer:

The correct ways to dynamically allocate memory for a struct named MyStruct are:

• MyStruct *m = malloc( sizeof(MyStruct) );

• MyStruct *m = (MyStruct *) malloc( sizeof(MyStruct) );