Defining structures - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of structure member assignment

What is the output of this C program?

C

#include <stdio.h>

struct Point {
    int x;
    int y;
};

int main() {
    struct Point p1;
    p1.x = 5;
    p1.y = 10;
    printf("%d %d\n", p1.x, p1.y);
    return 0;
}

A Compilation error

B 10 5

C 5 10

D 0 0

💡 Hint

Remember how structure members are assigned and accessed.

The structure 'Point' has two integer members x and y. We assign 5 to x and 10 to y, then print them in order. So output is '5 10'.

❓ Predict Output

intermediate

Size of structure with padding

What is the output of this program printing the size of the structure?

C

#include <stdio.h>

struct Data {
    char a;
    int b;
};

int main() {
    printf("%zu\n", sizeof(struct Data));
    return 0;
}

A 4

B 5

C 6

D 8

💡 Hint

Think about how the compiler aligns data in memory.

The structure has a char (1 byte) and an int (usually 4 bytes). Due to padding for alignment, the total size is 8 bytes, not 5.

🔧 Debug

advanced

Identify the error in structure initialization

What error will this code produce when compiled?

C

#include <stdio.h>

struct Person {
    char name[10];
    int age;
};

int main() {
    struct Person p = {"Alice", 30, 100};
    printf("%s %d\n", p.name, p.age);
    return 0;
}

A Compilation error: too many initializers

B Runs and prints: Alice 30

C Runtime error: segmentation fault

D Compilation error: missing semicolon

💡 Hint

Check how many values are given for initialization compared to members.

The structure has two members but three values are given in initialization. This causes a compilation error for too many initializers.

❓ Predict Output

advanced

Output of nested structures

What is the output of this program?

C

#include <stdio.h>

struct Date {
    int day;
    int month;
    int year;
};

struct Event {
    char name[20];
    struct Date date;
};

int main() {
    struct Event e = {"Meeting", {15, 8, 2024}};
    printf("%s on %d/%d/%d\n", e.name, e.date.day, e.date.month, e.date.year);
    return 0;
}

A Meeting on 8/15/2024

B Meeting on 15/8/2024

C Compilation error

D Meeting on 0/0/0

💡 Hint

Look at how nested structures are initialized and accessed.

The nested structure Date is initialized with day=15, month=8, year=2024. The print statement outputs these values in order.

🧠 Conceptual

expert

Number of items in an array of structures

Given this code, how many elements does the array 'books' contain?

C

struct Book {
    char title[50];
    int pages;
};

struct Book books[] = {
    {"Book A", 100},
    {"Book B", 150},
    {"Book C", 200}
};

A 3

B 2

C 0

D 50

💡 Hint

Count the number of initializers in the array.

The array 'books' is initialized with three elements, so it contains 3 items.