SUM             --- OK  (made up of correct characters, not too long)
MyValue         --- OK  (upper and lower case letters can be used)
SUM23           --- OK  (digits can be used after the first letter)
GRAND TOTAL     --- BAD (no spaces allowed)
16Candles       --- BAD (digits can't be used as first character)
YEAR%           --- BAD (last character % means this is an integer variable)

Case Differences in Names

Look at the last rule again:

If two names differ only in upper and lower case characters, they are really the same name.

This means that:

VALUE     Value     value     vALuE

are really all the same name. In fact, if you try to use more than one of these versions in your program, the QBasic system will change what you have typed so that only one version is used. Say that you have typed in the following program:

' Attempt to use two versions of the same name
'
LET VALUE = 123
PRINT value

As soon as you move the cursor out of the PRINT statement the QBasic system will change your program:

' Attempt to use two versions of the same name
'
LET value = 123
PRINT value

VALUES      value
VALU        vALUe
VALUE$      Value