solution for out of memory error ????

>> name=uigetfile('*.*');
file_open=fopen(name,'r');
file_read=fread(file_open,'uint8');
fclose(file_open);
a=file_read;
Max=max(histc(a,unique(a)));
L=zeros(length(a),1);
x=a;
>> BWT=zeros(length(a),Max+1);  
*    Out of memory. Type HELP MEMORY for
  your options.*

If any one can help me what this out of memory means typed help memory but was not able to resolve in fact undertsand ths