Thanks,
I have been using INCOMM rather than INPUT$ because the GSM MODEM sends some data that is not delimited by a CR character.
I also have been using INCOMM because the GSM MODEM uses the pair of characters, CR and LF, as end of line markers. INPUT$ leaves the terminating LF in the buffer and it becomes the first character of the next string.
Many of the messages from the GSM MODEM do not fit within the string length limitations of 70 characters, so I have been using DM[] to for a lot of the string manipulations.
I think that the use of DM[] as an extended buffer space is an excellent idea. I will have to ask Mr. R. Tito to drop the BAUD rate to 9600 to ensure that the receive buffer will not overflow between scans.
Thanks for the suggestion.
Gary D.