Lecture 9

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Questions and Answers

Given a structure defined as `struct item { int id; float price; };`, and assuming `sizeof(int)` is 4 bytes and `sizeof(float)` is 4 bytes, what is the size of `struct item` and how is the memory allocated?

8 bytes, with `id` and `price` stored contiguously in memory.
It depends on the compiler. If it's a 16-bit compiler, it might be smaller than 8 bytes, but on a 64-bit compiler, it will always be 8 bytes.
Potentially more than 8 bytes due to possible padding added by the compiler to optimize memory access, but `id` and `price` are still contiguous. (correct)
4 bytes, with the `id` and `price` members overlapping in memory.

If you have a structure `struct point { int x; int y; };` and a pointer `struct point *p;`, which of the following is the correct method to access the `x` member of the structure pointed to by `p`?

Both B and C (correct)
`p->x`
`(*p).x`
`p.x`

Consider a scenario where you need to define a structure representing network packets. Which of the following is the most accurate description of how bitwise structures could be utilized?

To dynamically allocate memory for each part of a network packet, giving developers more control over where packet data is located in memory.
To create arrays of structures, which is especially useful for implementing network protocols via look-up tables.
To pack packet header fields (e.g., flags, sequence numbers) into specific numbers of bits within a larger data type to conserve memory. (correct)
To define the structure layout so it can be directly mapped to a function's parameters.

You have a structure representing a complex number: `struct complex { double real; double imaginary; };`. You want to write a function that adds two complex numbers. Which of the following function signatures is most appropriate, assuming you want to modify the first complex number in-place with the result?

<code>void add_complex(struct complex *a, struct complex b)</code> (D) Signup and view all the answers

Suppose you have an array of structures: `struct point points[10];` where `struct point` is defined as `struct point { int x; int y; };`. Which of the following correctly represents how to access the `y` coordinate of the 5th element in the array?

<code>points[5].y</code> (C) Signup and view all the answers

Given the following structure definition `typedef struct { int id; char name[20]; float score; } STUDENT;`, and assuming `sizeof(int)` is 4 bytes, `sizeof(char)` is 1 byte, and `sizeof(float)` is 4 bytes, what is the most likely reason for `sizeof(STUDENT)` equalling 28 bytes, rather than 28 bytes as one might expect?

The compiler adds padding to ensure that data members are properly aligned in memory, potentially increasing the structure's size. (B) Signup and view all the answers

Consider the code snippet:

typedef struct { int x; int y; } POINT;
POINT p1 = {320, 100};
POINT p2;
p2 = p1;
p1.x = 500;

What are the values of p2.x and p1.x after the execution of this code?

<code>p2.x</code> is 320 and <code>p1.x</code> is 500 (D) Signup and view all the answers

Given the structure:

typedef struct { int id; char name[20]; float score; } STUDENT;
STUDENT s1 = {1234, "John", 88.0};
STUDENT s2 = {5678, "William"};

What is the value of s2.score after this declaration?

0.0 (C) Signup and view all the answers

Which of the following statements about `typedef` is most accurate?

It creates an alias or a synonym for an existing data type. (D) Signup and view all the answers

Consider the following code snippet:

typedef struct { int x; int y; } POINT;
POINT p1 = {320, 100};

printf("%d,%d", p1.x, p1.y);

What will be the output of the printf statement?

"320,100" (C) Signup and view all the answers

Given the following nested structure definitions:

typedef struct {
 char first_name[50];
 char last_name[50];
} NAME;

typedef struct {
 int year;
 int month;
 int day;
} DATE;

typedef struct {
 int id;
 NAME name;
 DATE dob;
} PERSON;

PERSON p1;

Which of the following statements correctly initializes the day field of the dob member of the PERSON struct p1?

<code>p1.dob.day = 15;</code> (A) Signup and view all the answers

Consider the following code snippet involving structure pointers:

typedef struct {
 int x;
 int y;
} POINT;

POINT p1;
POINT *ptr = &p1;

p1.x = 10;

Which of the following expressions is NOT equivalent to accessing the x member of the p1 structure through the pointer ptr?

<code>&ptr->x</code> (C) Signup and view all the answers

What is the primary purpose of a self-referential structure?

To serve as building blocks for dynamic data structures like linked lists and trees. (D) Signup and view all the answers

Given the following self-referential structure and code:

typedef struct node {
 int val;
 struct node *next;
} NODE;

NODE n1, n2, n3;
n1.val = 5;
n2.val = 10;
n3.val = 15;
n1.next = &n2;
n2.next = &n3;
n3.next = NULL;
NODE *head = &n1;

What will be the output of the following code snippet?

printf("%d ", head->next->next->val);

15 (A) Signup and view all the answers

When a structure is passed as an argument to a function in C, what is the default behavior regarding how the structure's data is handled?

A copy of the structure is created and passed to the function; modifications within the function do not affect the original structure. (C) Signup and view all the answers

Flashcards

Structure Type

A user-defined data type containing a list of data members (elements), each with its own data type.

Size of a Structure

The sum of the sizes of all its members. Stored in contiguous memory cells, one after another.

Structure Type as Composite Data

A composite data type that combines different data types to construct structured hierarchical data types.