However, for species most commonly encountered in the database, self- explanatory codes are used. There are 16 of those codes. They are:

1. BOVIN for Bovine
2. CHICK for Chicken,
3. ECOLI for Escherichia coli
4. HORSE for Horse
5. HUMAN for Human
6. MAIZE for Maize (Zea mays)
7. MOUSE for Mouse
8. PEA for Garden pea (Pisum sativum)
9. PIG for Pig
10. RABIT for Rabbit
11. RAT for Rat
12. SHEEP for Sheep
13. SOYBN for Soybean (Glycine max)
14. TOBAC for Common tobacco (Nicotina tabacum),
15. WHEAT for Wheat (Triticum aestivum)
16. YEAST for Baker's yeast (Saccharomyces cerevisiae).

It is not possible to apply the above rules to viruses, so they are given arbitrary, but generally easy to remember, identification codes. In some cases it is not possible to assign a definitive code to a species. In these cases a temporary code is chosen. Examples of complete protein sequence entry names are: RL1_ECOLI for ribosomal protein L1 from Escherichia coli, FER_HALHA for ferredoxin from Halobacterium halobium. The names of all the presently defined species identification codes are listed in the SwissProt document file SPECLIST.TXT.