here is the programm:
{fid = fopen('francais.txt'); % francais is(les 3 poules)
b = fread(fid,21)';
fclose(fid);
a=dec2bin(b);
c=dec2hex(b);
str = native2unicode(b,'UTF-8');
disp(str);
fid = fopen('fichier3.txt'); %fichier3 is(trois)
b3 = fread(fid,'uint8')';
fclose(fid);
str3 = native2unicode(b3,'UTF-8');
disp(str3);
nbrasci=abs(str);
for i=1:1:length(str)
if nbrasci(i)==51
str=char([nbrasci(1:i-1),str3,nbrasci(i+1:length(str))]);
end
end}