Nested structures - Mini Project: Build & Apply

Working with Nested Structures in C

📖 Scenario: You are creating a simple program to store information about books in a library. Each book has a title, an author, and a publication year. The author itself has a first name and a last name.

🎯 Goal: Build a program that uses nested structures to store and display information about a book and its author.

📋 What You'll Learn

Define a structure called Author with firstName and lastName as character arrays.

Define a structure called Book that contains a title character array, an Author structure, and an year integer.

Create a variable of type Book and assign exact values to all fields.

Print the book's title, author's full name, and publication year.

💡 Why This Matters

🌍 Real World

Nested structures are used to model complex data like books with authors, addresses with cities, or employees with departments.

💼 Career

Understanding nested structures is important for jobs involving C programming, embedded systems, and software that manages structured data.

1

Define the nested structures

Define a structure called Author with firstName and lastName as character arrays of size 50 each. Then define a structure called Book that contains a title character array of size 100, an Author structure called author, and an integer year.

C

// Your code here

Hint

Use struct keyword to define both Author and Book structures. Remember to include the nested Author inside Book.

2

Create a book variable and assign values

Create a variable called myBook of type struct Book. Assign the title as "The C Programming Language", the author's first name as "Brian", last name as "Kernighan", and the year as 1978. Use strcpy to copy strings.

C

#include 
#include 

struct Author {
    char firstName[50];
    char lastName[50];
};

struct Book {
    char title[100];
    struct Author author;
    int year;
};

// Your code here

Hint

Remember to include string.h for strcpy. Use dot notation to access nested fields.

3

Write code to print book details

Inside the main function, after assigning values, write printf statements to print the book's title, author's full name (first and last name separated by a space), and publication year on separate lines.

C

#include 
#include 

struct Author {
    char firstName[50];
    char lastName[50];
};

struct Book {
    char title[100];
    struct Author author;
    int year;
};

int main() {
    struct Book myBook;
    strcpy(myBook.title, "The C Programming Language");
    strcpy(myBook.author.firstName, "Brian");
    strcpy(myBook.author.lastName, "Kernighan");
    myBook.year = 1978;
    // Print the book details below
    // Your code here
    return 0;
}

Hint

Use printf with format specifiers %s for strings and %d for integers. Access nested fields with dot notation.

4

Run the program and display output

Run the program and print the output exactly as shown:
Title: The C Programming Language
Author: Brian Kernighan
Year: 1978

C

#include 
#include 

struct Author {
    char firstName[50];
    char lastName[50];
};

struct Book {
    char title[100];
    struct Author author;
    int year;
};

int main() {
    struct Book myBook;
    strcpy(myBook.title, "The C Programming Language");
    strcpy(myBook.author.firstName, "Brian");
    strcpy(myBook.author.lastName, "Kernighan");
    myBook.year = 1978;
    printf("Title: %s\n", myBook.title);
    printf("Author: %s %s\n", myBook.author.firstName, myBook.author.lastName);
    printf("Year: %d\n", myBook.year);
    // Program output above
    // Your code here
    return 0;
}

Hint

Make sure your printf statements match the expected output exactly, including spaces and new lines.

Practice

1. What is a nested structure in C programming?

easy

A. A structure that contains another structure as a member

B. A structure with only one member

C. A structure declared inside a function

D. A structure that uses pointers only

Solution

1. Step 1: Understand structure composition

   A nested structure means one structure is included inside another as a member.

2. Step 2: Rule out distractors

   The other options describe unrelated concepts: a structure using pointers only, with only one member, or declared inside a function.

3. Final Answer:

   A structure that contains another structure as a member -> Option A

4. Quick Check:

   Nested structure = structure inside structure [OK]

Hint: Nested means one structure inside another [OK]

Common Mistakes:

• Thinking nested means pointer usage
• Confusing nested with single-member structures
• Assuming nested means declared inside functions

2. Which of the following is the correct syntax to access a member of a nested structure in C?

easy

A. outer.inner->member

B. outer->inner->member

C. outer.inner.member

D. outer->inner.member

Solution

1. Step 1: Identify access operator for nested structures

   When using nested structures (not pointers), use dot notation for each level: outer.inner.member.

2. Step 2: Understand pointer vs non-pointer access

   Arrow (->) is used only when accessing members through pointers, which is not stated here.

3. Final Answer:

   outer.inner.member -> Option C

4. Quick Check:

   Use dot for nested struct members [OK]

Hint: Use dot notation for nested struct members [OK]

Common Mistakes:

• Using arrow (->) when not using pointers
• Mixing dot and arrow incorrectly
• Confusing member access syntax

3. What is the output of the following C code?

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

typedef struct {
    char name[20];
    Date birthday;
} Person;

int main() {
    Person p = {"Alice", {15, 8, 1990}};
    printf("%d-%d-%d", p.birthday.day, p.birthday.month, p.birthday.year);
    return 0;
}

medium

A. 15-8-1990

B. Alice-15-8

C. 1990-8-15

D. Compilation error

Solution

1. Step 1: Understand structure initialization

   Person p is initialized with name "Alice" and birthday as Date {15, 8, 1990}.

2. Step 2: Trace printf output

   printf prints p.birthday.day (15), p.birthday.month (8), p.birthday.year (1990) separated by dashes.

3. Final Answer:

   15-8-1990 -> Option A

4. Quick Check:

   Print nested struct members correctly [OK]

Hint: Access nested members with dot notation [OK]

Common Mistakes:

• Printing name instead of date
• Mixing order of day, month, year
• Forgetting to initialize nested struct

4. Identify the error in this nested structure code snippet:

struct Address {
    char city[20];
    int zip;
};

struct Employee {
    char name[30];
    struct Address addr;
};

int main() {
    struct Employee emp;
    emp.addr->zip = 12345;
    return 0;
}

medium

A. Missing semicolon after struct definitions

B. Using '->' operator on a non-pointer structure variable

C. Incorrect declaration of nested structure

D. Cannot assign integer to zip member

Solution

1. Step 1: Check member access syntax

   emp.addr is a structure variable, not a pointer, so '->' operator is invalid here.

2. Step 2: Correct operator usage

   Use dot operator '.' to access zip: emp.addr.zip = 12345;

3. Final Answer:

   Using '->' operator on a non-pointer structure variable -> Option B

4. Quick Check:

   Use '.' for struct variables, '->' for pointers [OK]

Hint: Use '.' for struct, '->' only for pointers [OK]

Common Mistakes:

• Using '->' on struct variables
• Confusing pointer and non-pointer access
• Ignoring compiler error messages

5. Given the following nested structures, how would you write a function in C that takes a Person and returns the birth year?

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

typedef struct {
    char name[50];
    Date birthday;
} Person;

// Function prototype here

Which of the following is the correct function definition?

hard

A. int getBirthYear(Person *p) { return p.birthday->year; }

B. int getBirthYear(Person *p) { return p->birthday.year; }

C. int getBirthYear(Person p) { return p.year; }

D. int getBirthYear(Person p) { return p.birthday.year; }

Solution

1. Step 1: Understand parameter passing

   The function takes a Person by value, so use dot notation to access members.

2. Step 2: Access nested member correctly

   Access birthday.year as p.birthday.year since p is not a pointer.

3. Final Answer:

   int getBirthYear(Person p) { return p.birthday.year; } -> Option D

4. Quick Check:

   Use dot for struct value parameters [OK]

Hint: Use dot for struct, arrow for pointer parameters [OK]

Common Mistakes:

• Using arrow (->) on non-pointer parameter
• Accessing wrong member name
• Confusing pointer and value parameter syntax