Arrays and Pointers

Question 1

How is an array like a struct?

Answer 1

Both are aggregate data types.

Question 2

T/F: Arrays can contain more than one type.

Answer 2

F; the types need to be uniform.

Question 3

When adding the subscript operator ([]) to a variable declaration, what is the compiler being told to do?

Answer 3

Set aside contiguous blocks of memory (the number of blocks is given inside []), with each block of the data type’s size.

Question 4

T/F: When declaring an array, the size of the array must be a constant.

Answer 4

T

Question 5

Will the following code compile?

int nSize = 5;
int anArray[nSize];

Answer 5

No; ‘nSize’ must be const qualified for this to work.

Question 6

What is the syntax to access the member of a struct within an array?

Answer 6

arrayName[int index].memberName

Question 7

What is the difference between the following two declarations:

int anArray[5] = { 3, 2, 7, 5, 8 };

int anArray[5] = { 0 };

Answer 7

The first defines each element of the array with an initializer list, and the second sets all 5 elements of the array to 0.

Question 8

Will the following code compile?

int anArray[] = { 0, 1, 2, 3, 4 };

Answer 8

Yes; the compiler can extrapolate the size of the array from the length of the initializer list.

Question 9

How can sizeof() be used to get the number of elements in an array?

Answer 9

Divide the total allocated space by the size of a single element:

int nElements = sizeof(anArray) / sizeof(anArray[0]);

Question 10

Why use enums to index into an array?

Answer 10

To avoid magic numbers:

enum StudentNames
{
    KENNY, // 0
    KYLE, // 1
    STAN, // 2
    BUTTERS, // 3
    CARTMAN, // 4
    WENDY, // 5
    MAX_STUDENTS // 6
};

int anTestScores[MAX_STUDENTS]; // allocate 6 integers
anTestScores[STAN] = 76;

Question 11

What is the syntax to specify an array as a parameter?

Answer 11

typeName arrayName[]

Question 12

What does swap() do, and what is its library?

Answer 12

In swap(x, y), the values of the variables ‘x’ and ‘y’ are swapped. swap() is in the ‘algorithm’ library.

Question 13

Articulate the steps of a selection sort.

Answer 13

1) Starting at index 0, search the entire array to find the smallest value
2) Swap the smallest value found with the value at index 0
3) Repeat steps 1 & 2 starting from the next index

Question 14

What is the best way to initialize a multidimensional array?

Answer 14

With nested braces:

int anArray[3][5] =
{
{ 1, 2, 3, 4, 5, },
{ 6, 7, 8, 9, 10, },
{ 11, 12, 13, 14, 15 }
};

Question 15

T/F, you can leave out the first dimension but not the second when declaring a multidimensional array.

Answer 15

T; The compiler can figure out the first dimension but not the others (it ignores braces, so it cannot intuitively figure out the array’s dimensions; it only sees a string of digits).

Question 16

What is the length of the following C-style string:

char str[] = “string”;

Answer 16

7; the last is the ‘null’ character (ASCII code 0).

Question 17

What is a buffer?

Answer 17

A buffer is memory set aside temporarily to hold data.

Question 18

What is buffer overflow?

Answer 18

A buffer overflow occurs when the program tries to store more data in a buffer than the buffer can hold. Buffer overflow results in other memory being overwritten, which usually causes a program crash, but can cause any number of other issues.

Question 19

What is an advantage of using the ‘string’ library’s getline() function?

Answer 19

It reads in strings including whitespace:

cout &laquo_space;“Enter your full name: “;

string strName;
getline(cin, strName);

cout &laquo_space;“You entered: “&laquo_space;strName «endl;

Question 20

Explain the following declaration:

int *pnPtr = 0;

Answer 20

We are declaring a pointer and initializing it as a null pointer.

Question 21

How can a pointer be used as a boolean?

Answer 21

A null (or 0) pointer will evaluate to false. Remember that any value other than 0 is true!

if (pnPtr)
cout &laquo_space;“pnPtr is pointing to an integer.”;
else
cout &laquo_space;“pnPtr is a null pointer.”;

Question 22

What determines the size (in memory ) of a pointer (not its value)?

Answer 22

The architecture of the computer: 32 bit will have a 4 byte addressing scheme with 4 byte pointers, 64 bit will have 8, and so on.

Question 23

T/F: C-style strings follow all the same rules as arrays.

Answer 23

T; and they should be treated identically.