Chapter 2: 

RASPBERRY PI EVOLUTION

1. RPi1B: It was released in 2012 and is obsolete as of now, it has a CPU speed of 700 MHz single-core and 512MB of RAM. If you happen to have one lying around, there is a limit to what it can offer, you probably it can run a service or two that depend(s) on a few resources such as a file server or so. As with most of RPi variants, it has 2 USB 2.0 ports, a full HDMI port, 10GB ethernet, and a 3.5 audio jack. It is powered via a micro-USB port and is not that powerful; no more than 2 amps is needed to power it up. It is unique in having an AV port suitable for RCA connections of old monitors and TV sets. It accepts Full SD cards.

2. RPi 0 (W and WH): Its small size makes it unique in portable projects such as ID badges. It has a CPU speed of, dual-core and 512MB of RAM. Ports include a mini-HDMI, micro-USB 2.0 port. Its power is via micro-USB. Current can be as low as 1 amp which makes it suitable to be powered by portable batteries for on-the-go or portable projects. W and WH suffixes to some of its types stand for Wireless and Wireless along with Hard soldered Pins, not holes as in standard RPi0 to boost the functionality of the RPi0 but it still remains a less efficient one as compared with RPi2 and above. Its release date was back in 2015 and the following years saw the W and WH variants.

3. RPi2: released in 2013, A major improvement over RPi1 in terms of specs and resultant functionality use-case scenarios. The size was well reduced in size and GPIO pins increased in number, making it the standard design for future iterations of Raspberry Pi. It has a CPU of 1.2 GHz and 1 GB of RAM. It accepts MicroSD as its storage place. Of course, it is more efficient than RPi1 with more USB 2.0 ports of 4 along with HDMI, audio jack, and Ethernet port. This time it needs more amperage to power it up at least 2.5 to run smoothly. It lacks wifi and Bluetooth, but adapters can be used via USB ports.

4. RPi3: released in 2015 to include built-in wifi and Bluetooth with CPU speed increment to 1.3 quad-core keeping the rest of specs almost the same as RPi2.

5. RPI3B+: some improvements over RPi3B include a Gigabit Ethernet, AC wifi, and a slight speed increment. It was released in 2016.

6. RPi4B: the latest release in 2019 with flavors of initially 1GB of RAM that was soon replaced with 2GB along with 4GB and even 8GB RAM. CPU is of 1.5 GHz and quad-cores. There are also 2 USB 3.0 ports. This time the full-HDMI has been replaced with 2 Micro-HDMI for the possibility of having dual monitors. Power is delivered via USB Type C as it becomes the trend replacing the aging Micro-USB. It sports as well data delivery.

7. Compute Modules have no ports and only the core components. Various enclosures and their ports can be used with them as HDMI sticks, Hard Drive enclosures, and many more. Western Digital once opened a department called PiLabs to create such stuff.

So practically speaking only RPi 4B can act as a desktop computer with office suites, browsers, and data management software.