Of the options @Sulaymon Eshkabilov gives, (2) is by far the preferred solution to use as well as is creating a fully-qualified file name by using the <@doc:fullfile> function to catenate directory/folder strings to file name strings.
My personal favorite would be instead to use something more akin to
downloadDir='C:\Users\Public\Downloads'; % save the download root directory location
fn=fullfile(downloadDir,'age.txt'); % create the name
or, even easier, less data-specific
downloadDir='C:\Users\Public\Downloads'; % save the download root directory location
project='Homework'; % have a given place for the files to live
fn=fullfile(downloadDir,project,'*.txt'); % create a matching wildcard name for those wanted
d=dir(fn); % and return a dir() struct with matching files
for i=1:numel(d)
fn=fullfile(d(i).folder,d(i).name); % and get each name in turn...
%...read, process each here in turn...
...
end
