Compare local and global variables. Write a program with function to find area of rectangle in C with and without global variable.

Local and Global Variables:

1. Scope: The scope of a local variable is limited to the function or block in which it is declared while a global variable is accessible throughout the program.

2. Lifetime: The lifetime of a local variable lasts until the function or block in which it is declared is running. On the other hand, a global variable exists for the entire duration of the program.

3. Declaration: Local variables are declared inside a function or block, whereas global variables are declared outside all functions.

4. Default Value: Uninitialized local variables have garbage value. However, uninitialized global variables are automatically initialized to zero.

Now, let's write a program to find the area of a rectangle in C with and without global variables.

Program with global variables:

#include<stdio.h>

int length, breadth; // global variables

void findArea() {
    int area = length * breadth;
    printf("Area of rectangle is: %d", area);
}

int main() {
    printf("Enter length and breadth of rectangle: ");
    scanf("%d%d", &length, &breadth);
    findArea();
    return 0;
}

Program without global variables:

#include<stdio.h>

void findArea(int length, int breadth) {
    int area = length * breadth;
    printf("Area of rectangle is: %d", area);
}

int main() {
    int length, breadth;
    printf("Enter length and breadth of rectangle: ");
    scanf("%d%d", &length, &breadth);
    findArea(length, breadth);
    return 0;
}

In the first program, length and breadth are global variables, so they can be accessed directly inside the findArea function. In the second program, length and breadth are local to the main function and are passed to the findArea function as arguments.