Post

Week 8: Structures, Typedef, and Enumerations

Posted Updated
By
4 min read
Week 8: Structures, Typedef, and Enumerations

Overview

Welcome to Week 8 of C programming! This week, we will learn how to group different types of variables together using structures, define custom types with typedef, and create readable constant sets with enum.

By the end of this tutorial, you will:

  • Understand how to define and use struct
  • Pass structures to functions
  • Use arrays of structures
  • Use typedef and enum for more readable code

Time Breakdown

  • Structures and basic usage
  • Functions with structures
  • Arrays of structures
  • Enumerated types and typedef
  • Exercises & Q/A

1. Structures: Basics

Structures allow grouping variables of different types into a single unit.

Example 1: Basic Structure Declaration and Access

1
2
3
4
5
6
7
8
9
10
11
12
13

#include <stdio.h>

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

int main(void) {
    struct Date today = {26, 4, 2025};
    printf("Today's date is: %d/%d/%d\n", today.day, today.month, today.year);
    return 0;
}

Example Output:

1

Today's date is: 26/4/2025

2. Functions with Structures

Structures can be passed to functions as arguments.

Example 2: Update Date Using Structure and Function

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

#include <stdio.h>

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

void addOneDay(struct Date d) {
    d.day += 1;
    printf("Tomorrow's date is: %d/%d/%d\n", d.day, d.month, d.year);
}

int main(void) {
    struct Date today = {26, 4, 2025};
    addOneDay(today);
    return 0;
}

Example Output:

1

Tomorrow's date is: 27/4/2025

3. Arrays of Structures

Structures can be stored in arrays.

Example 3: Store Multiple Dates

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

#include <stdio.h>

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

int main(void) {
    struct Date events[2] = {{1, 5, 2025}, {10, 6, 2025}};
    for (int i = 0; i < 2; i++) {
        printf("Event %d date: %d/%d/%d\n", i+1, events[i].day, events[i].month, events[i].year);
    }
    return 0;
}

Example Output:

1
2

Event 1 date: 1/5/2025
Event 2 date: 10/6/2025

4. Enumerations and Typedef

Enums are used to assign readable names to integer constants.

Example 4: Enum Usage for Months

1
2
3
4
5
6
7
8
9

#include <stdio.h>

enum Month {JAN = 1, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC};

int main(void) {
    enum Month today = APR;
    printf("The current month number is: %d\n", today);
    return 0;
}

Example Output:

1

The current month number is: 4

Exercises

Exercise 1: Define and Print a Student Structure

  1. Define a Student structure with name (char array) and score (int).
  2. Create a student, input data, and print it.

Example Output:

1
2
3

Enter student name and score:
Alice 95
Alice scored 95 points.

Exercise 2: Add One Second to User-Input Time

  1. Define a Time structure with hour, minute, and second.
  2. Prompt the user to input hour, minute, and second.
  3. Write a function that adds one second to the input time, correctly handling overflow (i.e., 60 seconds → 1 minute, 60 minutes → 1 hour, 24 hours → 0).
  4. Print the new time.

Example Output:

1
2
3
4

Enter hour (0-23): 23
Enter minute (0-59): 59
Enter second (0-59): 59
New time: 00:00:00

Exercise 3: Map Months Using Enum

  1. Use enum Month to map a month number to its name.
  2. Print the corresponding month.

Example Output:

1
2

Enter month number (1-12): 5
Month number is: 5

Exercise 4: Use Typedef for Cleaner Struct

  1. Create a typedef for struct Book.
  2. Input and print book information.

Example Output:

1
2
3

Enter book title and number of pages:
CProgramming 500
Book: CProgramming, Pages: 500

Bonus Challenge

🏆 Complex Structure: Event Log Management

  1. You are asked to design a structure to manage event logs.
  2. Define a Date structure with day, month, and year.
  3. Define a Time structure with hour, minute, and second.
  4. Define a Log structure that contains both a Date and a Time, along with a short message (char[]).
  5. Ask the user to enter two event logs.
  6. After collecting input, print the logs in the following format:
1

[YYYY-MM-DD HH:MM:SS] Message

Example Output:

1
2
3
4
5
6
7
8
9
10
11

Enter date (day month year) for log 1: 26 4 2025
Enter time (hour minute second) for log 1: 14 30 15
Enter message for log 1: System rebooted

Enter date (day month year) for log 2: 26 4 2025
Enter time (hour minute second) for log 2: 16 45 00
Enter message for log 2: User login successful

Event Logs:
[2025-04-26 14:30:15] System rebooted
[2025-04-26 16:45:00] User login successful

Summary & Wrap-Up

  • Structures group different types of variables.
  • Structures can be passed to functions.
  • Arrays of structures are useful for managing collections.
  • Enums and typedef improve code readability.
Basis and Practice in Programming_DASF004_41, Exercices
struct typedef enum
This post is licensed under CC BY 4.0 by the author.