====== FAPPEND chnl:integer, file:string, access:integer, shrmod:integer ======
Use channel "chnl" to open file "file" in append mode with access mode "access" and share mode "shrmod"  

        valid channels:      0 - 7 [0 is used for script questionnaires]  
        valid access modes:  O_RD, O_WR, O_RW [should use O_RW]  
        valid share modes:   S_DN, S_DR, S_DW, S_DB  

**See also:** FOpen, FClose, FCreate