programming question

this code is taken from a PIC18C452 stepper motor driving application note, and when i try to run it in mplab, it doesnt seem to work.

I am using a PIC18F452 instead of the PIC18C452..does that affect the codes being used?


in this part of program what does UDATA_ACS actually mean?
my prgramming knowledge is very very limited so I hope there is someone to help

;******************************************************************
UDATA_ACS ;Relocatable variables in access RAM
STEP_NUMBER res 1 ;Used for tracking the microstep counts
MOTOR_DIRECTION res 1 ;Motor direction byte
;0 indicates Reverse rotation
;1 indicates forward
COUNTER res 1 ;Counter used for counting key debounce time
COUNTER1 res 1 ;Counter used for counting key debounce time
SPEED_REF_H res 1 ;Speed referance, read from ADC0, connected
SPEED_REF_L res 1 ;to Preset on the board
FLAG_BYTE res 1 ;Indicates status flags
STEP_JUMP res 1 ;Step jump count based on DIP switch setting
RECIEVED_BYTE res 1 ;Byte recieved from host PC
COMMAND_BYTE res 1 ;Command from host PC
INCH_VALUE res 2 ;Inch count from host PC
RPM_VALUE res 4 ;RPM value
MICRO_STEPS res 1 ;No. of microsteps stored
TEMP_RPM res 3 ;Temparary reg
TEMP_LOCATION res 4 ;Temparary reg
TEMP res 1 ;Temparary variable
TEMP1 res 1