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Advantages

1. Apropriate for positive selection on RNA viruses (Retrovirus), especially those whose ancestor sequences are not clear or unknown, such as HIV and Influenza
   
2. Identifying amino acids, which confer positive selection pressure
3. Application is very simple
4. Applying for large amount of sequences analysis (>thousands)

Drawbacks

    1. Premiary preparation of input data

• multiple alignment sequences
  
• codon format translation
  
• remove stop codon
• check empty colums in alignments
  

     2. Only DOS vertion

• can't work under Mac, Linux, Unix
• no debug and help function, very difficult to find problems when  run  into errors
• not open resource, can't read codes and make any modification
  

     3. Pylogeny is not taken into account
     4. False positive selection
     5. "Transition/Tranversion ratio" and "Codon Usage" are not taken into account
     6. Output format is text only, not compatable with other sequence analysis software/or program