分支结构：二分支 

                            if

                            endif

                 多分支

                         docase

                          endcase

 if嵌套

             if

              else

            endif

循环结构:

     当型循环

     do while 

    loop

    exit

     enddo

步长循环

for

loop

exit

endfor

表扫描循环

scan

loop

exit

endscan