It's rather a vague question?, but presuming you mean when actually programming the device? - you need 13V on MCLR, and 5V on both Vdd pins, the programming pins have 5V logic signals on them.
Meaning of the Data writing is writing to the EEPROM or writing to the memory when inputs given by the hardware.
So the correct word is Programming or Burning the chip.
Also there was a PIC16F877 version which can not program in PIC16PRO programmer. One of my friends also found that problem.
So better check with a PIC16F877A version with your parallel port programmer.
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