data test; a='A dataset'; run; %macro opends(name); %if %sysfunc(exist(&name)) %then %do; %let dsid=%sysfunc(open(&name,i)); %put data set &name; %end; %else %put Data set &name does not exist.; %mend opends; %opends(null); %opends(test); What will be written in the Log?

The macro uses %SYSFUNC(EXIST(&name)) to check dataset existence. NULL is a special SAS dataset name that doesn't create actual output, so EXIST returns false, triggering 'does not exist'. The TEST dataset was created by the preceding DATA step, so EXIST returns true, executing the %DO block and writing 'data set test'. The macro processes both calls sequentially.