is PIC 16F84 is a chip?

[swanair]

is there any difference between pic 16f84 and 16f84a?

[arran]

THe 16f84a is the newer version of the 16f84, microchip recomends using the a version for new projects. I'm not sure what the actual differences are you would have to read the datasheet to find out. One difference is that 16f84a doesn't contain lead which is now a legal requirement in the EU.