Closed Loop

Sir, 
linuxcnc 2.8.2 with a parallel port card can  do closed loop function over one axis.

Yes, see "etch servo" included with LinuxCNC.

    Thanks for supporting me,
Sir,
As per your suggestions i am making hal and ini file according etch servo hal and ini file and then run machine with this edited hal and ini file but machine axis are not moving and indicate joint 0 error.
so i am requesting kindly see these files and correct the mistake and i attached this hal and ini file.

Thanks for supporting me,
Sir,
As per your suggestions i am making hal and ini file according etch servo hal and ini file and then run machine with this edited hal and ini file but machine axis are not moving and indicate joint 0 error.
so i am requesting kindly see these files and correct the mistake and i attached this hal and ini file.

What are you trying to do?
The hal is a mess of closed loop and stepgen on the same axis X/joint 0, that will not work.

Thanks for reply,
Sir,
I am doing linuxcnc with parallel port computer and stepper motor and driver with linear glass encoder for one axis closed loop control.
for backlash and missing step problem  so kindly tell this is possible. 

I believe that it can be done, though it probably won't help with missed steps. If you miss a step then the PID will try "harder" which is likely to make it miss more steps.

It _might_ be possible to arrange to use adaptive feed to reduce speed when the PID error is high.

Looking at the HAL. Your stepgens are in position mode, and you connect stepgen.0.position-cmd to joint.0.motor-pos-cmd.

You have a PID, but the output is linked to a velocity signal, that then goes nowhere.

There are two ways to add a PID and encoders to a stepper system:

1) Run the stepgen in velocity mode (a lot like a servo) and have the PID control position.

2) Run open-loop position command, and add the PID offset on top as a position adjustment. In this mode you would use a sum2 component to add the PID output to the stepgen position command.

I actually don't know how the joint.0.motor-pos-fb fits in to this.
ie, what happens if you connect that pin to the encoder instead of to the stepgen. That's such an easy experiment that it has to be worth a try.

Thanks for supporting me,
Sir,
Kindly tell can you make this hal and ini file for parallel port computer and stepper motor and driver with linear glass encoder for one axis closed loop control.
I am agree for pay for these file.

Sorry, I don't mix money and LinuxCNC.

Try setting up the option 2 above, and let us know how it goes.