function BMI()
% This program calculates the BMI of a person. It allow for the program to
% be used worldwide and takes account for the Imperial and Metric systems
% for easy use.
clc;
clear;

% Displays the information to the user about the systems which can be used.
disp('                  --- BMI Calculator --- ');
disp('Please choose the measurement system you would like to use:');
disp('      1. Kilograms/Centimeters');
disp('      2. Pounds/Inches');
disp('      3. Pounds/Feet');
disp('      4. Stone/Inches');
optn = input('Please choose which system you would like to use. [1/2/3/4]: ');

% Checks to see which system the user has chosen and asks for the variables
% accordingly.
if optn == 1
    disp('Please input the your Weight, and Height');
    w = input('Your Weight(Kg) is? ');
    h = input('Your Height(cm) is? ');
    h1 = h / 100;
    BMI = round(w / h1^2);
    pause(1)

elseif optn == 2
    disp('Please input the your Weight, and Height');
    w = input('Your Weight(lbs) is? ');
    h = input('Your Height(in.) is? ');
    BMI = round((w / (h^2)*703));
    pause(1)

elseif optn == 3
    disp('Please input the your Weight, and Height');
    w = input('Your Weight(lbs) is? ');
    h = input('Your Height(ft) is? ');
    BMI = round((w / (h^2)*4.88));
    pause(1)

elseif optn == 4
    disp('Please input the your Weight, and Height');
    w = input('Your Weight(st) is? ');
    h = input('Your Height(in.) is? ');
    BMI = round((w / (h^2)*9840));
    pause(1)

else
    disp('Please choose a valid option.')
    pause(2.5)
    BMI();
end

% Displays the users BMI
disp(['Your BMI is: ', num2str(BMI)])

% Displays a message to the user about where they fall on the BMI scale and
% tells the user what their BMI means.
if BMI <= 18
    disp('You are very underweight and possibly malnourished.')
elseif BMI <20
    disp('You are underweight and could afford to gain a little weight.')
elseif BMI <=25
    disp('You have a healthy weight range for young and middle-aged adults.')
elseif BMI <=30
    disp('You are overweight')
elseif BMI > 30
    disp('You are obese')
end