How to include similar text files into a loop

I have 25 text files that include heights data from year 1991 to 2015. Each file contains only one column of data ( eg 40, 50, 120, 20, 62, 75, 15, 13, 25, 24…..) but the length of data in each file is different. The files are named like HGT1991, HGT1992…HGT2015. For each file, I need to find the number of data points that go below 40. How can I do this in a loop rather than doing the same thing for individual files for 25 times? And also I need to plot the data for each year. How I can call the file name as the title? Any help is appreciated.

Answer 1

[KSSV]

txtfiles = dir('*.txt'); % You are in the directory of text files
Nfiles = length(txtfiles) ;  % number of text files
% loop for each file 
for i = 1:Nfiles
fname = txtfiles(i).name ;   % file name
data = importdata(fname) ;   % import data from file
%%do what you want %%%
end

Answer 2

[Binu]

It worked really well. Thanks Siva