Week 8: Structures, Typedef, and Enumerations — Solution

Exercise Solutions

Exercise 1: Define and Print a Student Structure

#include <stdio.h>

struct Student {
    char name[30];
    int score;
};

int main(void) {
    struct Student s;
    printf("Enter student name and score:\n");
    scanf("%s %d", s.name, &s.score);
    printf("%s scored %d points.\n", s.name, s.score);
    return 0;
}

Example Output:

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

---

Exercise 2: Add One Second to a User-Input Time

#include <stdio.h>

struct Time {
    int hour;
    int minute;
    int second;
};

struct Time addOneSecond(struct Time t) {
    t.second += 1;
    if (t.second == 60) { t.second = 0; t.minute += 1; }
    if (t.minute == 60) { t.minute = 0; t.hour   += 1; }
    if (t.hour   == 24) { t.hour   = 0; }
    return t;
}

int main(void) {
    struct Time t;
    printf("Enter hour (0-23): ");   scanf("%d", &t.hour);
    printf("Enter minute (0-59): "); scanf("%d", &t.minute);
    printf("Enter second (0-59): "); scanf("%d", &t.second);

    t = addOneSecond(t);
    printf("New time: %02d:%02d:%02d\n", t.hour, t.minute, t.second);
    return 0;
}

Example Output:

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

---

Exercise 3: Map a Month Number to its Name Using Enum

#include <stdio.h>

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

int main(void) {
    int n;
    printf("Enter month number (1-12): ");
    scanf("%d", &n);

    const char *names[] = {
        "", "January", "February", "March", "April", "May", "June",
        "July", "August", "September", "October", "November", "December"
    };

    if (n >= JAN && n <= DEC) {
        printf("Month %d is %s\n", n, names[n]);
    } else {
        printf("Invalid month\n");
    }
    return 0;
}

Example Output:

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

---

Exercise 4: Use Typedef for a Cleaner Struct

#include <stdio.h>

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

int main(void) {
    Book b;
    printf("Enter book title and number of pages:\n");
    scanf("%s %d", b.title, &b.pages);
    printf("Book: %s, Pages: %d\n", b.title, b.pages);
    return 0;
}

Example Output:

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

---

Bonus Challenge: Event Log Management

#include <stdio.h>

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

typedef struct {
    int hour, minute, second;
} Time;

typedef struct {
    Date date;
    Time time;
    char message[100];
} Log;

void readLog(Log *l, int i) {
    printf("Enter date (day month year) for log %d: ", i);
    scanf("%d %d %d", &l->date.day, &l->date.month, &l->date.year);
    printf("Enter time (hour minute second) for log %d: ", i);
    scanf("%d %d %d", &l->time.hour, &l->time.minute, &l->time.second);
    printf("Enter message for log %d: ", i);
    getchar();
    fgets(l->message, sizeof(l->message), stdin);
}

void printLog(Log l) {
    printf("[%04d-%02d-%02d %02d:%02d:%02d] %s",
        l.date.year, l.date.month, l.date.day,
        l.time.hour, l.time.minute, l.time.second,
        l.message);
}

int main(void) {
    Log logs[2];
    readLog(&logs[0], 1);
    readLog(&logs[1], 2);

    printf("\nEvent Logs:\n");
    printLog(logs[0]);
    printLog(logs[1]);
    return 0;
}

Example Output:

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