求问CHKTRE(ICODE)这个函数

ycjwanok

这边要用到 但看不明白 问问各位  CHKTRE(ICODE)函数是什么作用的？ 返回值个表示什么意思？
手册里给的解释如下
CALL CHKTRE(ICODE)
6 W& k) ?$ m' R" }$ s- O$ u5 ]2 HIf the case contains Type 4 (or greater) buses with in-service branches then an error condition is
2 M  \! c5 O9 o3 K- ereturned. Counts number of islands not containing a Type 3 (swing) bus. It may be inappropriate to
call this subroutine with generators converted; since there will be no Type 3 buses, it will simply
count every island (finding at least one unless there is no working case).
9 w0 C* R1 Q; T- O- tICODE Error code (integer output):
. v1 Z$ v# G: t/ L0 No errors.
7 v, q, t8 x4 }# ]-1 No in-service buses remaining.
8 U4 ^# w4 X- I& F-2 There are Type 4 buses with in-service branches connected.
>0 Number of islands without a Type 3 bus.
+ f# |0 y& A- v4 C3 R: K% N太谢谢了