请问大家：我提交有些sas程序（如下）时log中出现这样的语句。请问uninitialized代表什么问题？谢谢。

程序一：（这个程序的问题是compute glucrange时没有对analysis变量加其statistic后缀）
proc report data=sasuser.diabetes nowd;
   column sex weight fastgluc postgluc GlucRange;
   where age>40;
   define weight / format=comma6.2 spacing=4 width=7;
   define sex / order width=7 spacing=4 center
                'Sex of/Patient';
   define fastgluc / 'Fasting/Glucose';
   define postgluc / 'Postprandial/Glucose' width=12;
   define glucrange / computed 'Glucose/Range';
   compute glucrange;
      glucrange=postgluc-fastgluc;
   endcomp;
run;



log中出现：
NOTE: Variable fastgluc is uninitialized.
NOTE: Variable postgluc is uninitialized.


程序二：（这是仿照sas base的一道考题编的）
data chen;
       set sasuser.admit;
       file 'c:\users\administrator\my documents\my sas files\9.2\added.sas7bdat';
      put lastname $ qtr1 qtr2 qtr3 qtr4;
run;



log中出现：
NOTE: Variable lastname is uninitialized.
NOTE: Variable qtr1 is uninitialized.
NOTE: Variable qtr2 is uninitialized.
NOTE: Variable qtr3 is uninitialized.
NOTE: Variable qtr4 is uninitialized.