How to declare/construct functions in MATLAB.

Functions are the m-files or MATLAB files that use input and output parameters to operate on some values given by user(inputs) and then display their results(outputs).
  To declare/costruct functions open the editor/new script.
  Wright the function definition/prototype in the first line,i.e
   Function definition è function[o1,o2,o3...]=function_name(i1,i2,i3...) 

Where high lighted area is function definition, in which 

Ä     Function is the key word that is necessary to tell MATLAB that we are gonna declare/build a function.

Ä o1,o2,o3 and up-to so-on are representing output1,output2,output3 etc, you can use some other                     keywords in-place of o1,o2,o3 etc

Ä  = is assignment operator.

Ä    function_name is used to tell you people that it's the place where you can give a name to your function.

Ä i1,i2,i3 and up-to so-on are representing input1,input2,input3 etc you can use some other                              keywords in-place of i1,i2,i3 etc

Ä    Note that outputs should be enclosed in square brackets i.e [ ], and inputs should be enclosed in
        parenthesis i.e ( )

? Then save your function note that while saving it you have to use the function_name as m-file name because they both should match in order to call it.
 for example

function that calculates sum and diff. of two inputs.

To download the above function click below.