How to specify a range for string characters?

Yes, you should be able to write:

IF dishr NOT BETWEEN '00' AND '23' then flag = 'Invalid';

or

IF NOT (dishr BETWEEN '00' AND '23') then flag = 'Invalid';

More info: http://support.sas.com/documentation/cdl/en/lrcon/62955/HTML/default/viewer.htm#a000999255.htm

You may also look at Fully Bounded Range Condition

If nothing will work then you may use the classic expression:

IF dishr < '00' OR dishr > '23' then flag = 'Invalid';

Can the user enter 0A ?
If so then that is in that range.

If they are limited to entering only numeric characters it will work.
If they can enter anything then test for a numeric string first then the range test.

mlmcc

Good point!  This possibility should solve some input mask.

I'm using SAS version 8.2.  And it does not recognize the clause "BETWEEN".  Is there some other keyword that I can use?  Thanks.

So long as you don't have an issue with non-numeric characters you should be able to do something like

dishr  >= '00' AND dishr <= '23'

mlmcc

I wrote it in the first answer already:

IF dishr < '00' OR dishr > '23' then flag = 'Invalid';

I incorporated the suggested line of coding and it is not working.  Below is test sample of what I coded:
========================
data test;
  infile datalines;
  input dishr $;
  flag='';
  IF dishr < '00' or dishr > '23' then flag = 'InValid';
  else flag='Valid';
datalines;
'01'
'03'
'23'
'~1'
'1~'
'25'
'A0'
'a2'
'2t'
;
proc print data=test;
run;
============================

I need to be able detect anything that is entered that is not in the range of '00' through '03' is to be set as invalid.  So if the data has a character in the string then it is set to invalid; if the data has a numeric range that falls outside of the range '00'-'23', it is set to invalid.

I don't know why SAS is setting all observation as Invalid.  What am I doing wrong?

If your data contain alphabetic characters then you cannot use above formula as stated by mlmcc already.

You have several options...

You could use IN() function and list all valid values (if your SAS version supports it):

 IF dishr IN ('00', '01', '02',   ...    ,'23') then flag = 'Valid';

You could test the value for non-digit characters by NOTDIGIT function and then use standard IF.

You could also convert your character data into a number by INPUT() function and then simply check the numeric value range.

Etc.

Just open the SAS documentation and read about available functions.

None of the suggestions worked due to using an older version of SAS - i.e., version 8.2.