Lab 12 – Active Structures in C

PSUC Lab 12 — Composite Data Structures

Active Logic: Structures (`struct`)

Master user-defined composite data types in C: struct definition, member access operator (.), arrow operator (->), array of structures, structure sorting, and date arithmetic.

Structure Memory & Member Rules

Concept	Syntax / Rule	Key Trap / Pitfall
Member Access	`p1.name` or `ptr->name`	Use `.` for structure variable, `->` for pointer!
Nested Struct	`p1.doj.day`	Inner structure member accessed sequentially
Structure Swap	`temp = s[j]; s[j] = s[j+1]; s[j+1] = temp;`	Entire structure assignment copies all members at once!
Date Addition	Add days, rollover month if `d > daysInMonth`	Leap year February has 29 days!

🎯 Learning Philosophy: Active Logic Building

Test your structure logic across 3 Interactive Learning Modes:

🧠 Tab 1 (Logic & Hints): Struct layout & member access.
🧩 Tab 2 (Logic Puzzle): Complete missing dot/arrow operators & test live date calculators!
💻 Tab 3 (C Solution): Reference verified C code solutions.

Solve structure logic puzzles before peeking at C reference code!

Exercise 1 of 4

Personal Information Structure (`struct Personal`)

Defines nested structure containing personal name, date of joining (day, month, year), and salary.

Nested Structure Definition

struct Date { int day, month, year; };
struct Personal { char name[50]; struct Date doj; float salary; };
Accessing DOJ: p1.doj.day

Interactive Logic Hints

💡 Hint 1: Can a structure contain another structure as member? ▼

Yes! This is called Nested Structure!

🧩 Complete Member Access Operators

struct Personal p1;
scanf("%s", p1name);
scanf("%d", &p1dojday);

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👤 Personal Profile Generator

Name:

Salary (Rs):

Profile summary...

personal_struct.cReference C Code

#include <stdio.h>

struct Date { int day, month, year; };
struct Personal {
    char name[50];
    struct Date doj;
    float salary;
};

int main() {
    struct Personal p1 = {"Abhay Bisht", {15, 8, 2024}, 75000.0};

    printf("Name: %s\n", p1.name);
    printf("DOJ: %02d/%02d/%d\n", p1.doj.day, p1.doj.month, p1.doj.year);
    printf("Salary: Rs. %.2f\n", p1.salary);
    return 0;
}

Exercise 2 of 4

Student Array Sorted by Total Marks

Sorts an array of student structures in decreasing order of total marks.

Structure Array Sorting

Compare totals: if (s[j].total < s[j + 1].total)
Swap entire structures: struct Student temp = s[j]; s[j] = s[j+1]; s[j+1] = temp;

Interactive Logic Hints

💡 Hint 1: Can we swap whole struct variables with single = sign? ▼

YES! C supports direct assignment struct_a = struct_b! All members copy automatically!

🧩 Complete Decreasing Order Swap

if (s[j].total s[j + 1].total) {
  struct Student temp = s[j];
  s[j] = s[];
  s[j + 1] = ;
}

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🎓 Student Merit Rank Generator

Sorted Merit List...

student_sort.cReference C Code

#include <stdio.h>

struct Student {
    int roll; char name[50]; float total;
};

int main() {
    struct Student s[3] = {
        {101, "Rahul", 245.5}, {102, "Priya", 289.0}, {103, "Amit", 210.0}
    };

    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2 - i; j++) {
            if (s[j].total < s[j + 1].total) {
                struct Student temp = s[j];
                s[j] = s[j + 1];
                s[j + 1] = temp;
            }
        }
    }

    printf("Merit List:\n");
    for (int i = 0; i < 3; i++) {
        printf("Rank %d: %s (Total: %.1f)\n", i + 1, s[i].name, s[i].total);
    }
    return 0;
}

Exercise 3 of 4

Employee Net Salary & Filter

Computes Net Salary (Net = Basic + DA + HRA) and filters employees earning above average.

Salary Breakdown Formula

DA = basic * 0.52 | HRA = basic * 0.15
netSalary = basic + DA + HRA

Interactive Logic Hints

💡 Hint 1: How to filter above-average earners? ▼

Compute total company salary average first, then loop again: if (e[i].net > avgNet) print(e[i]);

🧩 Complete Net Salary Calculation

e[i].da = e[i].basic * ;
e[i].hra = e[i].basic * ;
e[i].net = e[i].basic e[i].da + e[i].hra;

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💼 Employee Net Salary Visualizer

Net salary breakdown...

emp_salary.cReference C Code

#include <stdio.h>

struct Employee {
    char name[50]; float basic, da, hra, net;
};

int main() {
    struct Employee e[3] = {
        {"Suresh", 30000}, {"Ramesh", 45000}, {"Mahesh", 50000}
    };
    float totalNet = 0;

    for (int i = 0; i < 3; i++) {
        e[i].da = e[i].basic * 0.52;
        e[i].hra = e[i].basic * 0.15;
        e[i].net = e[i].basic + e[i].da + e[i].hra;
        totalNet += e[i].net;
    }
    float avgNet = totalNet / 3.0;
    printf("Avg Net Salary = Rs. %.2f\nAbove Avg Earners:\n", avgNet);
    for (int i = 0; i < 3; i++) {
        if (e[i].net > avgNet) printf("%s: Rs. %.2f\n", e[i].name, e[i].net);
    }
    return 0;
}

Exercise 4 of 4

Date Addition Algorithm (+45 Days)

Adds 45 days to current date and handles month/year rollovers accurately.

Month Rollover Logic

Add 45: d.day += 45;
Loop: while (d.day > getDaysInMonth(d.month, d.year))
Deduct month days: d.day -= daysInMonth; d.month++;
Year rollover: if (d.month > 12) { d.month = 1; d.year++; }

Interactive Logic Hints

💡 Hint 1: What about Leap Years? ▼

February has 29 days if year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)!

🧩 Complete Date Addition Rollover Loop

d.day += 45;
while (d.day > daysInMonth(d.month, d.year)) {
  d.day daysInMonth(d.month, d.year);
  d.month;
  if (d.month > 12) { d.month = 1; d.year; }
}

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📅 Date Addition (+45 Days) Calculator

Day (1-31):

Month (1-12):

Year:

Date addition result...

date_add.cReference C Code

#include <stdio.h>
#include <stdbool.h>

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

bool isLeap(int y) { return (y%400==0 || (y%4==0 && y%100!=0)); }
int daysInMonth(int m, int y) {
    int days[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    if (m == 2 && isLeap(y)) return 29;
    return days[m];
}

int main() {
    struct Date d = {15, 8, 2024};
    d.day += 45;

    while (d.day > daysInMonth(d.month, d.year)) {
        d.day -= daysInMonth(d.month, d.year);
        d.month++;
        if (d.month > 12) { d.month = 1; d.year++; }
    }
    printf("New Date (+45 days): %02d/%02d/%d\n", d.day, d.month, d.year);
    return 0;
}

Knowledge Check

Test Your Structures Mastery

Question 1 of 5

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Active Logic: Structures (struct)

Structure Memory & Member Rules

🎯 Learning Philosophy: Active Logic Building

Personal Information Structure (struct Personal)

Nested Structure Definition

Interactive Logic Hints

🧩 Complete Member Access Operators

👤 Personal Profile Generator

Student Array Sorted by Total Marks

Structure Array Sorting

Interactive Logic Hints

🧩 Complete Decreasing Order Swap

🎓 Student Merit Rank Generator

Employee Net Salary & Filter

Salary Breakdown Formula

Interactive Logic Hints

🧩 Complete Net Salary Calculation

💼 Employee Net Salary Visualizer

Date Addition Algorithm (+45 Days)

Month Rollover Logic

Interactive Logic Hints

🧩 Complete Date Addition Rollover Loop

📅 Date Addition (+45 Days) Calculator

Test Your Structures Mastery

Active Logic: Structures (`struct`)

Personal Information Structure (`struct Personal`)