简单的两个数比较的程序：
%LET A=10;
%LET B=20;
%IF &A>&B %THEN C =&A;
%ELSE C =&B;
%put &C;

log中的报错：
1    %LET A=10;
2    %LET B=20;
3    %IF &A>&B %THEN C =&A;
ERROR: The %IF statement is not valid in open code.
4    %ELSE C =&B;
ERROR: The %ELSE statement is not valid in open code.
5    %put &C;
WARNING: Apparent symbolic reference C not resolved.
&C

不解，望指教！！
谢谢！！