tux penguin

PC introduction

The basic PC

Home PCs are avaiable in a veriety of sizes determined by what compnents are included and how much space is allowed for additional or replacement componets. I will compare the two end of the spectrum - the Raspberry pi 2 and the a desktop PC. Other variationa like notepads and laptop lie in between these two. The are some elements that all PCs require, while there are many other that are optional.

CPU

The central processing unit (usually just called the processor) is the chip that runs your applications.

Main memory

These are the chips used to hold a copies of the applications that are currently running and their data. Their contents are lost when the PC is turned off.

Graphics card

In early PCs the image on the screen was created using a graphics card that just held some memory and simple circuitry to convert the contents of the memory into pixels on the screen.

Modern PCs are capable of very complex graphic effects that are used in video games. These require powerful processors designed specifically for this task and a modern "video card" may be:

Primary storage device

The programs and data used by the PC are held on some form of storage device - most commonly a hard disk or a solid state drive SSD (special memory chips that retain their contents when the PC is turned off).

External connectors

A PC will have external connectors for attaching:

Motherboard

This circuit board holds:

A minimal PC

An example of minimal PC is the Raspberry Pi.
Raspberry Pi introduction
Even a low powered PC like this will allow you to do most of the things you want to do:

Extra abilities of a full size PC

A new full size PC has these increased or additional capabilities
Here is list starting with the processor, memory and graphics that can't be changed on the Pi.

More processing power

Typical new home PCs may have an Intel i3 or i5 processor.
These something the order of ten times the procssing power.
This will not make surfing the web any faster and won't even be diccernable for most of the tasks you do on a PC.
There are however some important exceptions where this extra power is crucial e.g.:

In a desktop PC the processor can be replaced with a more powerful one although this often means changing the motherboard as well.

Memory

The pi 2 has 1GB of memory. A typical new desktop PC has 8GB or more.
The amount of memory required to run the operating system and applications varies coniderable. My Pi 2 is currently running the Raspbian operating system, a web browser, an editor, a web server and database server while using less than a quarter of its memory.
By contrast, a Windows operating system may use more than twice this amount before any application are started.
If a full sixed PC requires additional memory there are sockets on the motherboard to fit it. No additional memory can be added to the Pi.

More powerful graphics processing with more memory

Even a basic video card (including those integrated with the CPU and using shared memeory) are capable of drawing large detailed graphical users interfaces and playing DVDs.
Tasks that require more powerful cards include:

If a full sixed PC require a more powerful graphics card it can added to a slot on the motherboard. On the pi it is integrated into the CPU chip and can not be replaced.

Greater storage capacity

The storage capacity of the Pi is initially dictated by the size of the SD card (typically 8GB to 64GB) you put in it. Additional storage can be connected using a USB memory stick or external USB hard drive, so TBs of storage can be used. The storage capacity of a new full size PC is initially dictated by the size of hard disk (typically 1TB). Additional storage can be added by adding another hard drive inside the PC case or using an external USB hard drive. The files that consume the greatest amount of storage space on a home computer are generally the operating system, applications, vidoes and photos.

Optical drives

Optical drives are CDs, DVD, and blue ray. One of these will usually be included in a full size PC. A portal reader can be added to a USB port on a Pi.
Optical drives are used for:

Ethernet connector

Both the Pi and desktop machines have a an Ethernet port for making wired connections to your home network by connecting directly to an ADSL modem router. This is lacking on slimlime devices like netbooks because of the size of the connector. These rely on wireless ntworking.

Wireless network adapter

The Pi 3 and modern PCs have a wireless adaptor built in that allows them to connect wirelessly to a home, public or office network. Older versions of the Pi and older PCs require a wireless adaptor plugged in to a USB port.

Why most PCs are not the size of a credit card

There are several reasons why most PCs are so much larger than the credit card sized Pi:

Finally, many people buy a full sized PC with Windows because they do not really know what they are going to use it for so buy something much more expensive than they need when Raspbrry Pi was sufficient.

Portable PCs

Portable PCs can be roughly divided into netbooks and laptops.
Both have built:

A notebook uses a solid state drive (SSD) for ite primary storage. A laptop may use an SSD or small (in physical size) hard drive for ite primary storage. A large laptop will have an optical drive - a smaller laptop or netbook won't. Hence, laptops are bigger, heavier and more expensive. Indeed, while a netbook is generally cheaper than a desktop PC, a laptop is generally more expensive.

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