_rom(read only memory):bo nho chi doc thong tin---la bo nho co dinh chung ta chi co the doc thong tin ma ho duoc pep gi.khi mat thong tin ko bi xoa .bo nho rom chua thong tin venha sx va chuong trinh co ban dieu khien viec nhap xuat du lieu rom-bios .----                      *ram(random access memory):bonho thong tin---lavung nho truy cap ngau nhien chung ta co the doc ghi va luu giu thong tin tam yhoi len vung nho ram khi mat nguon dien thong tin se bi xoa ,khpi bat may tinh thong tin trog ram la rong,