Most of the scripts files that one ultimately use will be function M files. These files again have the .m extensions, but they are used in a different way than scripts. Function files have input and output arguments, and behave like other programming subroutines like in C and Java languages.
 
The structure of a typical function file, say dummyfunction.m is as follows :

function outputs = dummyfunction(inputs)
code
.
..
…
Outputs = …

must note here that name of the .m file is same as the function name. Let’s make a file here :

Step 1 : make a matlab file

Create a dummyFunction.m file in the matlab directory, in which you are working on.

% function <output> = <function name>(<input parameters>)
function y = dummyFunction(x) 
count = 0; % variable declaration and definition
for i = 0: x % starting for loop
   count = count+1
end

Note that the word function appears at the start of the file, and in lower case letters.

Step 2 : Call that function from matlab.

>> dummyFunction(10)

count =
     1

count =
     2

count =
     3

count =
     4

count =
     5

count =
     6

count =
     7

count =
     8

count =
     9

count =
    10

count =
    11