Fid=-1 for fopen

So I am trying to open a bunch of .dat files(ex:frm_ais_edr_nnnn.dat', where n varys), so when I put it in a loop , fopen works for first time and when the loop runs for the second time and it takes next .dat fil fopen returns fid=-1 and it cannot be processed. the Code is as below:

 clear;
 clc;
 filepath='C:\Users\K chetan\Desktop\marsis_DAta\datafiles';
 out=dir(filepath);
 n = length(out);
 for count=3:n
   out(count,1).name
   fid=fopen(out(count,1).name,'r');
   data_file= fread(fid,'*char');
   fclose(fid);
 end

here the file path is the directory in which all files are present.

How can I overcome this error ?

the error its showing is

count =

       4

fid =

      -1

Error using fread
Invalid file identifier.  Use
fopen to generate a valid file
identifier.

Error in directory_test (line 8)
    data_file= fread(fid,'*char');

thank you

Answer 1

[Walter Roberson]

     fid = fopen( fullfile(filepath, out(count,1).name), 'r');

[ck]

will I need to put this in a loop?

[ck]

YEAH ! it worked , thanks a ton!