An antivirus program(1)a virus by searching code recognized as that of one of the thousands of viruses known to afflict computer systems. An antivirus program also can be used to create a checksum for(2)files on your disk, save the checksums in a special file, and then use the statistic to(3)whether the files are modified by some new virus. Terminate and stay resident (TSR) programs can check for unusual(4)to access vital disk areas and system files, and check files you copy into memory to be sure they are not(5).