# A03.m - Calculating the Fine Structure Constant using Pre-Defined Variables

% loads the variables stored in the file constants.mat into memory load('constants'); % calculate the fine structure constant alpha = e^2 / (hbar * c * 4 * pi * eps0); % display the reciprical of the fine structure consant to 5 decimal places fprintf('fine structure constant = 1 / %.5f\n',1/alpha)

This program demonstrates how to read in a .mat file that has previously defined variables and use those variables in a simple calculation. The command `load` command will read in variables if the argument is a `.mat` file and will read in data values if it is an ASCII file (more on that later).

The `constants.mat` file contains values for the following constants all defined in MKS units:

- G = Gravitational constant
- c = speed of light
- e = fundamental charge
- eV = electron volt (in Joules)
- eps0 = permittivity of free space
- h = Planck's constant
- hbar = Planck's constant / 2 pi
- k = Boltzmann constant
- me = mass of electron
- mn = mass of neutron
- mp = mass of proton
- mu0 = permeability of free space
- u = atomic mass unit

Feel free to download this file and add to it or customize it to your needs. To save the variables defined in memory to a file, simply use the command `save('filename')`. Matlab will automatically add the `.mat` file extension.