PIC 8-bit classification

The low-end PICs, which operate on data 8-bits at a time, are divided into three architectural families:

Baseline (12-bit instructions)

These PICs are based on the original PIC architecture, going back to the 1970’s and General
Instrument’s “Peripheral Interface Controller”.
They are quite limited, but, within their limitations (such as no interrupts), they are simple to work
with – particularly in assembler.
Modern examples include the 6-pin 10F series, the 8-pin 12F509 and the 14-pin 16F506

Midrange (14-bit instructions)

This is an extension of the baseline architecture, adding support for interrupts, more memory and
on-chip timers and peripherals, including PWM (pulse width modulation) for motor control,
support for serial, I2C and SPI interfaces and LCD (liquid crystal display) controllers.
Modern examples include the 8-pin 12F629, the 20-pin 16F690 and 40-pin 16F887

High-end (16-bit instructions)

Otherwise known as the 18F series, this architecture overcomes some of the limitations of the
midrange devices, providing for more memory (up to 128k program memory and almost 4k data
memory) and advanced peripherals, including USB, Ethernet and CAN (controller area network)
connectivity.
The 18F architecture is designed to support C programming, and is the only one of the 8-bit PIC families for which Microchip offer a C compiler.
An excellent PIC programmer to start with is
Microchip’s PICkit 2 shown below

PIC16fXX Block Diagram