function disp_num(a,fmt)
% disp_num(a,fmt): display binary representation of numbers 
% a = number or array to be displayed
% fmt = format, 'int', 'single', or 'double'
% binary digits are displayed in groups of 16
% NOTE: the bytes are in a different order than actually stored in memory 
% but they conform to what is in the book

% write a into file
file='disp.tmp';
fid=fopen(file,'w');
fwrite(fid,a,fmt);
% now read for display
fclose(fid);
fid=fopen(file,'r');
t=fread(fid,inf,'uint16');
fclose(fid);
switch fmt
case {'int','single'}
    w=2;
case {'double'}
    w=4;
otherwise
    error('unknown format')
end
% permute as 2 1 4 3 6 5 etc
r=reshape(1:length(t),w,length(t)/w);
r=flipdim(r,1);
[m,n]=size(r);
for j=1:n,
    for i=1:m,
        rr=r(i,j);
        fprintf('%s ',dec2bin(t(rr),16));
    end
    fprintf('\n');
end
return