** from page 45 of Intdoc03.pdf ;
** A data flag is the variable name plus underscore.
** So, for example, the data flag for SALARYX is SALARYX_
** However if the varname has 8 characters, then position 5 is replaced
** with an underscore, i.e. WELFAREX has flag WELF_REX .
** If position 5 is already an underscore, it becomes zero:
Variable  Data Flag  Rule 
--------  ---------  ----
SALARYX   SALARYX_   if length(varname)<8, Add underscore to signify data flag 
WELFAREX  WELF_REX   else if varname has 8 char., make 5 an underscore
EDUC_REF  EDUC0REF   else if 5 is already _ , make it a zero.

Data flag values:
-----------------
"A"="valid blank"
"B"="invalid response"
"C"="don't know, refusal, or other non-response"
"D"="valid or good data value"
"T"="topcoded"
"H"="expenditure has been allocated to other rec. w/the orig. exp. being overwritten with blank
"R"="false state code for nondisclosure reasons"

Abbreviations:
--------------
CU="Conumer Unit"

NEWID=CU identification # .  Digits 1-7 uniquely identify CU. 8 is interview #, 2-5. 
CUID=1st 7 digits of NEWID.
REPSTAT: 1="Complete income respondent" 2="Incomplete income respondent"