• Status: Solved
  • Priority: Low
  • Security: Public
  • Views: 97
  • Last Modified:

Why is a printer object necessary when printing via copy to com1?

Hello out there,

a customer called telling me that her label printer stopped working correctly. She uses an application which creates spool files and send them directly to the printer via copy to com1.
The printer's operating LED is blinking, that is all which happens when the command:
copy spool.txt com1 is issued. (The file does contain IPL-Code, which is the printer's language). Other PCs at customer's site work fine.

We found out, that it is neccessary to have a printer installed in Windows (Control panel->printers and faxes) and connect it in the printer's settings to the COM-port to which it is connected.

My question: Why does a printer need to be installed (the generic / text only driver is sufficient) in windows when we commuicate directly to COM1 (Command Prompt)? The blinking of the printer's LED suggests that at least some data is being sent to the printer...

As it took us some hours to solve the issue (someone must have deleted the printer definition) I would like to have an explanation why this is necessary. I have always thought that when "talking" directly to the printer via COM-port the driver would be circumvented. I also found some hints that a printer definition may block the associated COM-port for other applications.

Any help here is highly appreciated as I need to tell my customer the reason for the mentioned behaviour.

Greetings from Berlin, Germany
Friedhelm Feller-Przybyl
Friedhelm Feller-Przybyl
1 Solution
Dave BaldwinFixer of ProblemsCommented:
Is it actually a USB printer connection?  If so, the COM port doesn't exist without the printer driver.

What is the command she is using?
David Johnson, CD, MVPOwnerCommented:
Your assumption that file.txt > com1: directly accesses hardware is flawed
Windows NT consists of several rings user mode being the highest in number but lowest in permissions. All access to hardware requires a driver and the driver accesses the hardware.  Even in the earliest days of computing one accessed hardware via the bios using int 13 calls.
Friedhelm Feller-PrzybylSoftware EngineerAuthor Commented:
thank you!
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Keep up with what's happening at Experts Exchange!

Sign up to receive Decoded, a new monthly digest with product updates, feature release info, continuing education opportunities, and more.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now