Lab 4 – Active Control Structures: Switch Case

PSUC Lab 4 — Menu-Driven Control Structures

Active Logic: Switch-Case Statements

Master menu-driven programming, break statement mechanics, fallthrough behavior, default fallback handling, and multi-tier billing calculations.

Switch-Case Syntax Rules

Component	Syntax Rule	Key Trap / Pitfall
Expression Type	`switch (expr)`	Must evaluate to `int` or `char`! (No float/double)
Case Labels	`case constant:`	Must be compile-time constants (e.g. `case 1:` or `case 'A':`)
Break Statement	`break;`	Omitting break causes fallthrough into next cases!
Default Case	`default:`	Executes when no case constant matches

🎯 Learning Philosophy: Active Logic Building

Test your menu-driven logic across 3 Interactive Learning Modes:

🧠 Tab 1 (Logic & Hints): Concept breakdown & fallthrough rules.
🧩 Tab 2 (Logic Puzzle): Complete missing switch, case, break, & default keywords!
💻 Tab 3 (C Solution): Reference verified C code solutions.

Solve the switch-case logic puzzles before viewing reference code!

Exercise 1 of 6

Menu-Driven Area Calculator (Circle, Rectangle, Triangle)

Select shapes from a menu (1=Circle, 2=Rectangle, 3=Triangle) and branch to the correct formula using switch-case.

Shape Formulas

Case 1 (Circle): area = 3.14159 * r * r
Case 2 (Rectangle): area = l * w
Case 3 (Triangle): area = 0.5 * b * h
Default: Invalid choice notification

Interactive Logic Hints

💡 Hint 1: What happens if break is omitted after case 1? ▼

C will execute case 1 AND fallthrough directly into case 2 and case 3! Always include break;!

🧩 Complete the Switch-Case Menu Code

(choice) {
   1:
    area = 3.14159 * r * r;
    ;
  :
    printf("Invalid");
}

Select keywords above and click Check!

📐 Area Menu Calculator

Choose Shape:

Result will appear here...

ex1_area.cReference C Code

#include <stdio.h>
#define PI 3.14159

int main() {
    int choice;
    float r, l, w, b, h, area;

    printf("1. Circle\n2. Rectangle\n3. Triangle\nEnter choice: ");
    scanf("%d", &choice);

    switch (choice) {
        case 1:
            printf("Enter radius: "); scanf("%f", &r);
            area = PI * r * r;
            printf("Area of Circle = %.2f\n", area);
            break;
        case 2:
            printf("Enter length & width: "); scanf("%f %f", &l, &w);
            area = l * w;
            printf("Area of Rectangle = %.2f\n", area);
            break;
        case 3:
            printf("Enter base & height: "); scanf("%f %f", &b, &h);
            area = 0.5 * b * h;
            printf("Area of Triangle = %.2f\n", area);
            break;
        default:
            printf("Invalid Choice!\n");
    }
    return 0;
}

Exercise 2 of 6

Fallthrough Experiment (Switch Without Break)

Demonstrates what happens when break statements are omitted: execution "falls through" to all subsequent cases!

Fallthrough Behavior

When a matching case is found, C jumps to it.
Without break;, CPU does NOT re-check case labels — it simply executes every line below it until the end of switch!

Interactive Logic Hints

💡 Hint 1: Is fallthrough always a bug? ▼

No! Intentional fallthrough is used to group multiple cases together (e.g. case 'a': case 'e': case 'i': ...).

🧩 Fallthrough & Break Practice Puzzle

Fill in C keywords below to control fallthrough execution in switch statement:

switch (choice) {
  case 1: printf("Circle Area\n");
  case 2: printf("Rectangle Area\n");
   printf("Invalid Choice\n");
}

Select statements above and click Check!

🧪 Test Fallthrough Interactively

Select Input Choice:

Execution sequence...

ex2_fallthrough.cReference C Code

#include <stdio.h>

int main() {
    int choice = 1;
    switch (choice) {
        case 1: printf("Circle Area\n");    // No break!
        case 2: printf("Rectangle Area\n"); // No break!
        case 3: printf("Triangle Area\n");  // No break!
        default: printf("Invalid Choice\n");
    }
    return 0;
}

Exercise 3 of 6

Day of Week & Arithmetic Calculator

Translate day numbers (1=Sunday..7=Saturday) and perform menu-driven arithmetic operations (+, -, *, /).

Char Switch Case

Operands for calculator: switch (op) where op is char
case '+': res = a + b; break;
case '/': res = a / b; break; (Check b != 0)

Interactive Logic Hints

💡 Hint 1: Can we use char in switch statements? ▼

Yes! In C, characters are internally stored as integer ASCII values (e.g. '+' is ASCII 43).

🧩 Complete the Arithmetic Operator Switch

char op = '+'; float a = 10, b = 5;
switch (op) {
  case :
    res = a + b; ;
  case :
    res = a / b; break;
}

Select options above and click Check!

📅 Day Translator & Calculator

Day (1-7):

Operator:

Result will show here...

calc_switch.cReference C Code

#include <stdio.h>

int main() {
    char op; float a = 10, b = 5;
    scanf(" %c", &op);
    switch (op) {
        case '+': printf("Result = %.2f\n", a + b); break;
        case '-': printf("Result = %.2f\n", a - b); break;
        case '*': printf("Result = %.2f\n", a * b); break;
        case '/': if (b!=0) printf("Result = %.2f\n", a / b); break;
        default:  printf("Invalid Operator\n");
    }
    return 0;
}

Exercise 4 of 6

Internet Browsing Bill Calculator

Computes browsing charges: 1 hour = Rs 20, 1 minute = Rs 1, Unlimited Day Pass = Rs 200 using switch-case menu.

Pricing Rates

Option 1 (Hours): Bill = Hours * Rs 20
Option 2 (Minutes): Bill = Minutes * Rs 1
Option 3 (Day Pass): Flat Rs 200

Interactive Logic Hints

💡 Hint 1: What menu choice structure works best? ▼

Prompt user for Choice (1-3), then input duration inside the specific case!

🧩 Complete the Internet Bill Switch Logic

switch (choice) {
  case 1: bill = hours * ; break;
  case 2: bill = mins * ; break;
  case 3: bill = ; break;
}

Verify rate values above and click Check!

🌐 Internet Bill Calculator

Plan Choice:

Duration (Units):

Bill output...

internet_bill.cReference C Code

#include <stdio.h>

int main() {
    int choice, units; float bill = 0;
    printf("1. Hours 2. Mins 3. Unlimited\nChoice: ");
    scanf("%d", &choice);

    switch (choice) {
        case 1: scanf("%d", &units); bill = units * 20.0; break;
        case 2: scanf("%d", &units); bill = units * 1.0;  break;
        case 3: bill = 200.0; break;
        default: printf("Invalid Plan\n");
    }
    printf("Total Bill = Rs. %.2f\n", bill);
    return 0;
}

Exercise 5 of 6

Tiered Electricity Bill Calculator (Switch Category)

Computes electricity charges based on unit slabs: Tier 1 (1–100 units = Rs 3/unit), Tier 2 (101–200 units = Rs 5/unit), Tier 3 (>200 units = Rs 8/unit).

Tier Slabs

Category 1 (1-100 units): bill = units * 3.0
Category 2 (101-200 units): bill = 300 + (units - 100) * 5.0
Category 3 (>200 units): bill = 800 + (units - 200) * 8.0

Interactive Logic Hints

💡 Hint 1: How to convert continuous units into switch cases? ▼

Use integer category mapping: category = (units <= 100) ? 1 : ((units <= 200) ? 2 : 3);!

🧩 Complete Tiered Electricity Calculation

switch (category) {
  case 1: bill = units * ; break;
  case 2: bill = 300 + (units - 100) * ; break;
  case 3: bill = 800 + (units - 200) * ; break;
}

Verify tier rates above and click Check!

⚡ Electricity Bill Calculator

Units Consumed:

Bill breakdown...

electricity_bill.cReference C Code

#include <stdio.h>

int main() {
    int units, category; float bill;
    printf("Enter units consumed: ");
    scanf("%d", &units);

    category = (units <= 100) ? 1 : ((units <= 200) ? 2 : 3);

    switch (category) {
        case 1: bill = units * 3.0; break;
        case 2: bill = 300.0 + (units - 100) * 5.0; break;
        case 3: bill = 800.0 + (units - 200) * 8.0; break;
    }
    printf("Electricity Bill = Rs. %.2f\n", bill);
    return 0;
}

Exercise 6 of 6

Shopping Discount Calculator (Customer Tier)

Applies customer type discounts: VIP (20% discount), Regular (10% discount), Student (15% discount) using switch-case.

Discount Rules

'V' (VIP): 20% off → finalAmount = amount * 0.80
'S' (Student): 15% off → finalAmount = amount * 0.85
'R' (Regular): 10% off → finalAmount = amount * 0.90

Interactive Logic Hints

💡 Hint 1: How to compute net payable amount? ▼

Multiply total amount by (1.0 - discountRate)!

🧩 Complete the Discount Switch Logic

switch (custType) {
  case 'V': disc = ; break;
  case 'S': disc = ; break;
  case 'R': disc = ; break;
}

Verify rates above and click Check!

🛍️ Shopping Discount Calculator

Customer Type:

Purchase Amount (Rs):

Discount output...

shopping_discount.cReference C Code

#include <stdio.h>

int main() {
    char type; float amount, disc = 0.0, finalAmt;
    printf("Enter type (V/S/R) & amount: ");
    scanf(" %c %f", &type, &amount);

    switch (type) {
        case 'V': case 'v': disc = 0.20; break;
        case 'S': case 's': disc = 0.15; break;
        case 'R': case 'r': disc = 0.10; break;
        default: printf("Invalid Type\n");
    }
    finalAmt = amount * (1.0 - disc);
    printf("Discount = %.2f, Net Payable = Rs. %.2f\n", amount * disc, finalAmt);
    return 0;
}

Knowledge Check

Test Your Switch-Case Control Mastery

Question 1 of 5

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