16F877 have an internal eeprom alowing you to store your data.
to write to internal eeprom. Use WRITE and READ instructions from PICBASIC.

If you have a lot of data let's say more than internal F877 one, you can use external EEPROM like 93c46, 24C04, 24LC64 and others.

F877 has internal EEPROM 2K (or 256 * 8bit) lets say 256 allocations space for a BYTE size variable... not too bad

regards¸