I don't think I have ever encounted a .5M file format.
Please experiment with the following and tell us what you find:
filename = 'AppropriateFileName.5M';
[fid, msg] = fopen(filename, 'r');
if fid < 0
error('Could not open file "%s" because "%s"', filename, msg);
end
bytes = fread(fid, [1 128], '*uint8');
fclose(fid);
if isempty(bytes)
error('file "%s" was empty\n', filename);
elseif numel(bytes) < 128
fprintf('Note: file "%s" is only %d bytes long\n', numel(bytes));
end
fprintf('File "%s"\n\nFirst bytes as text:\n\n%s\n', char(bytes));
fprintf('First bytes as hex\n')
fprintf('%02x ', bytes); fprintf('\n');
