Embedded System - Raspberry Pi
Burn the OS SD Card
The Raspberry Pi that you would get with basic price(around 35 USD) would not comes with any preloaded operating system. You may get the one with preloaded OS in a SD card, but you would need to pay extra cost. In my case, I decided to buy a basic hardware and SD card separately and burn the SD card with an operating system on my own because I set this process(i.e, burning OS SD Card) as one of my learning topics as well.
In most of YouTube, it may look very simple like just downloading the OS file, unzip it and copy all the files onto SD card. But I am a little bit suspicious about many of those videos.. I think they will work but they might have missed some procedure that they have done before they made the video. Since any media (e.g, SD Card, Hard Disk) with bootable operating system requires a specific format and specific program(e.g, boot loader) placed in a specific location on the media, just following up those YouTube may or may not work when you try on your own.
So I would decide to go through a kind of formal procedure intruduced in Raspberry Pi official site and want to summarize what I went through in this page. It may look a little bit complicated than you might have expected if you want to use Raspberry Pi just as a low cost PC, but I may be a good study(training) topics if you want to use for a basic embedded system tool.
Usually this process is not that simple and require several cumbersome procedure, but luckily raspberry org has released very easy-to-use tool called Pi Imager on May 2020. If you want to install (burn) an OS released after May 2020, you can burn it into the SD card using Pi Imager. But if you want to install the older versions of OS you would need to do it in older method. I wrote on two separate procedure for old method (manual burning) and new method (Pi Imager) as linked below.