Lifetime and scope comparison - Mini Project: Build & Apply

Lifetime and Scope Comparison in C

📖 Scenario: Imagine you are organizing a small event and need to keep track of the number of guests in different rooms. You want to understand how variables behave inside and outside functions in C.

🎯 Goal: You will create a simple C program to compare the lifetime and scope of variables declared globally, locally inside a function, and as static inside a function.

📋 What You'll Learn

Create a global variable called guest_count initialized to 10

Create a function called update_guest_count that declares a local variable guest_count initialized to 5

Inside update_guest_count, declare a static variable static_guest_count initialized to 0 and increment it by 1 each time the function is called

Print the values of the global guest_count, local guest_count, and static_guest_count inside the function

Call update_guest_count three times from main and print the global guest_count after each call

💡 Why This Matters

🌍 Real World

Understanding variable lifetime and scope helps in managing data correctly in programs, avoiding bugs related to unexpected variable changes.

💼 Career

Many programming jobs require knowledge of how variables behave in memory and across function calls, especially in systems programming and embedded development.

1

Create the global variable

Create a global integer variable called guest_count and set it to 10.

C

# Create a global variable guest_count and set it to 10
// Your code here

Need a hint?

Global variables are declared outside any function.

2

Create the update_guest_count function

Create a function called update_guest_count that declares a local integer variable guest_count set to 5. Inside the function, declare a static integer variable static_guest_count initialized to 0. Increment static_guest_count by 1 each time the function is called.

C

int guest_count = 10;

// Create function update_guest_count with local guest_count=5 and static static_guest_count=0
// Increment static_guest_count by 1 inside the function
// Your code here

Need a hint?

Static variables keep their value between function calls.

3

Print variable values inside update_guest_count

Inside the update_guest_count function, add printf statements to print the values of the global guest_count (print this before declaring the local variable), the local guest_count, and the static_guest_count.

C

int guest_count = 10;

void update_guest_count() {
    int guest_count = 5;
    static int static_guest_count = 0;
    static_guest_count++;
    // Print local guest_count
    // Print static_guest_count
    // Print global guest_count
    // Your code here
}

Need a hint?

Use printf to show values. To access and print the global guest_count, place its printf before declaring the local guest_count to avoid shadowing.

4

Call update_guest_count and print global guest_count in main

Create a main function that calls update_guest_count three times. After each call, print the global guest_count using printf.

C

int guest_count = 10;

#include 

void update_guest_count() {
    printf("Global guest_count: %d\n", guest_count);
    int guest_count = 5;
    static int static_guest_count = 0;
    static_guest_count++;
    printf("Local guest_count: %d\n", guest_count);
    printf("Static guest_count: %d\n", static_guest_count);
}

// Create main function
// Call update_guest_count three times
// Print global guest_count after each call
// Your code here

Need a hint?

Remember to include return 0; in main.