dlmwrite is printing the wrong number

dlmwrite('a.txt',288230387962871929,'precision',40);

Creates a file with one number listed:

288230387962871940

I thought this might be due to using a 32-bit version of MATLAB. I then tried with a machine running 64-bit MATLAB, I got:

288230387962871936

Why doesn't it print 288230387962871929 like I asked it to ?

Answer 1

[Star Strider]

The reason it is writing ‘288230387962871936’ instead of ‘288230387962871929’ is explained by the error the ‘qd’ calculations throws in this code snippet:

qb = dec2bin(288230387962871929);
qd = bin2dec(qb);

Error using bin2dec (line 35)
Binary string must be 52 bits or less.