That is just what you told the PIC to do.

porta = 1 ' 0000 0001
portc = 1 ' 0000 0001
pause 1000
porta = 0
portc = 0


porta = 255 ' 1111 1111
portc = 255 ' 1111 1111
pause 1000
porta = 0
portc = 0


First code sets bit 0 only, second code sets all bits for the port