Just get in the habit of checking for your keys before you go through any door. It takes no mental effort once it's a habit. If they aren't in your pocket (or in my case a lanyard) then they are in that room or vehicle, so you should recover them before going out. This method worked for me 100% for decades. It only failed after I got married and my wife started stealing them. But it's usually not too hard to find her.
My neighbor at the trailer park was a janitor at the university. I built my computer from parts he salvaged from the recycle bin, and put Redhat 5 on it.
On Archlinux at least, the glibc package includes info pages for C functions. Just type info libc at the command line, or use info inside emacs. There are hyperlinks in info pages, it's a nicer interface than man pages.
PulseEffects can moderate the high-volumed sounds too. It has a complex set of controls and filters, and I'm not a sound engineer, so I just followed someone else's recipe.
My middle school algebra teacher sparked my interest in coding.
Due to moving around a lot, I never learned any mathematics, not even basic arithmetic before middle school. In the seventh grade, I was put in a class where the teacher just handed out worksheets with arithmetic problems, and then usually left the classroom until the end of the hour. On the rare occasions when she stayed, I asked her to teach me arithmetic, but she didn't believe I couldn't do it, so she never taught me and I failed the class.
But in the eighth or ninth grade, they allowed me to sign up for the Algebra for dummies class, which taught in two semesters what the normal class taught in one. My new teacher taught me arithmetic the first day, and I was his star pupil from that point.
He invited me and some other students to stay after school to learn FORTRAN. We did not have a computer at the middle school--it was at the university. We didn't even have a card punching machine. So we had cards that looked like punch cards, but instead of punching holes in them, we coded the Hollerith code in them by filling bubbles with a number 2 pencil. Then we sent the cards on a mail truck to the university and got back a printout a week later.
On my computer,
ps -ef | grep Xorg
gives
root 642 632 0 06:09 tty7 00:03:26 /usr/lib/Xorg :0 -seat seat0 -auth /run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
showing that the X server is running. I suspect that when you run the above ps command, that you will get no output, which shows that the X server is not running on your computer. In that case, you need to remove the lock that is preventing it from starting:
rm /tmp/.X0-lock
I don't have any need to edit markdown, but I sometimes use Marker: “Simple yet robust Markdown editor made with GTK” as a viewer.
It might be possible to boot into a bootable image from grub so you don't need to set up another bootable partition.
Or you could disable your display manager in systemd. This will start in console, then if you want X just run startx.
Or you could change your display manager to Lemur, which supports X, Wayland, and TTY sessions.
Or you could just press control-alt-F2 at the login screen to switch to a console.
$ info {command}
although not available for all commands will often give texts that are more tutorial in nature. If you don't like the interface of info, you can use tkinfo instead.