An excerpt from the PrimerGen's documentation: PrimerGen searches strings of amino acid residues in order to reverse-translate oligonucletide primers of a desired range of lengths and maximum number of degeneracies. PrimerGen only works on IBM-PC(TM), XT, AT, PS/2 and compatibles with EGA or VGA graphics adaptors. It will not work on computers with CGA or Hercules(TM) graphics cards. This is because the program alters the screen fonts which cannot be done on the latter types of graphics adaptors. I have no access to XGA card-driven computers, so I don't know what happens there! A hard drive is NOT required and PrimerGen will fit on a 360K 5.25" floppy disk. You need to input: - the appropriate amino acid sequence, - the minimum size of desired primers, - the maximum size of primers (important for codon preference - generated primers), - the maximum acceptable number of mismatches, - desired codon preference table (if required). The program will also supply the melting temperature of the primer. You may input the Na or K cation concentration used in the melting temperature calculations. PrimerGen contains a sequence editor, where amino acid residues are entered. The amino acid sequence must be ONE fragment and cannot be longer than 70 residues. The sequence must be in the ONE LETTER CODE and cannot contain any UNKNOWNS. After the desired amino acid sequence has been entered have the option of saving the sequence to a disk. PrimerGen will also accept and re-edit previously saved sequence files, and also contains a codon preference table editor.