Agreed. I wasn’t trying to say they are always better just explain the difference.

I almost exclusivity use Linux and it handles this great. .so libraries are stored with a version number and a link to the latest. So math3.so and math4.so with math.so being a link to math4.so. that way if needed I can set a program to use math3.so and keep everything else on the latest version.

So the basic purpose of a library is to allow code that does some useful thing to be easily used in multiple programs. Like say math functions beyond what is in the language it self or creating network connections.

When you build a program with multiple source files there are many steps. First each file compiled into an object file. This is machine code but wherever you have calls into other files it just inserted a note that basicly says connect this call to this part of another file. So for example connect this call to SquareRoot function in Math library.

After that has been done to every file needed then the linker steps in. It grabs all the object files combines them into one big file and then looks for all the notes that say connect this call to that function and replaces them with actual calls to the address where it put that function.

That is static linking. All the code ends up in a big executable. Simple but it has two big problems. The first is size. Doing it this way means every program that takes the squareroot of something has a copy of the entire math library. This adds up. Second is if there is an error in the math library every program needs to be rebuilt for the fix to apply.

Enter dynamic linking. With that the linker replaces the note to connect to the SquareRoot function in math library with code that requests the connection be made by the operating system.

Then when the program is run the OS gets a list of the libraries needed by the program, finds them, copies them into the memory reserved for that program, and connects them. These are .so files on Linux and .dll on Windows.

Now the os only needs one copy of math.so and if there is a error in the library a update of math.so can fix all the programs that use it.

For GPL vs LGPL this is an important distinction. The main difference between them is how they treat libraries. (There are other differences and this is not legal advice)

So if math.so is GPL and your code uses it as a static link or a dynamic link you have to providd a copy of the source code for your entire program with any executable and licence it to them under the GPL.

With LGPL it’s different. If math.so is staticly linked it acts similar to the GPL. If it’s dynamicly linked you only have to provide the source to build math.so and licences it under LGPL. So you don’t have to give away all your source code but you do have to provide any changes to the math library you made. So if you added a cubeRoot function to the math library you would need to provide that.

If you don’t code with undefined behavior compiler updates can apply to legacy code. I’ve been through enough compiler upgrades with microcontrollers that it’s old hat.

The nice thing is if a much better solution exists then a rust compiler that uses it can be implemented using it. Then you don’t have to rewrite all the rust code.

For ntsc vhs players it wasnt a component in the vcr that was made for copy protection. They would add garbled color burst signals. This would desync the automatic color burst sync system on the vcr.

CRT TVs didn’t need this component but some fancy tvs would also have the same problem with macrovission.

The color burst system was actually a pretty cool invention from the time broadcast started to add color. They needed to be able stay compatible with existing black and white tv.

The solution was to not change the black and white image being sent but add the color offset information on a higher frequency and color TVs would combine the signals.

This was easy for CRT as the electron beam would sweep across the screen changing intensity as it hit each black and white pixel.

To display color each black and white pixel was a RGB triangle of pixels. So you would add small offset to the beam up or down to make it more or less green and left or right to adjust the red and blue.

Those adjustment knobs on old tvs were in part you manually targeting the beam adjustment to hit the pixels just right.

VCRs didn’t usually have these adjustments so they needed a auto system to keep the color synced in the recording.

Pretty specific use case. A normal OS handleds time slicing and core assignment for processes and uses it’s judgement for that. So at any time your process can be suspended and you don’t know when you get your next time slice.

Same with when you make wait calls. You might say wait 100ms but it may be much longer before your process gets to run again.

In a real time OS if you have real time priority the OS will suspend anything else including it self to give you the time you request. It also won’t suspend you no matter how long you use the core.

So if you need to control a process with extreme precision like a chemical manufacturing process, medical device, or flying a rocket where being 10ms late means failure they are required.

However with great power comes great responsibility. You need to make sure your code calls sleep frequently enough that other tasks have time to run. Including things like file io or the gui.

Cool. I remember having to use Red Hawk Linux years ago. It’s a real time variant of Red Hat. It was such a pain to get the dependencies workin on it.

It’s a hot mess. Or it was 10 years when I was last forced to use it.

I remember there was one setting I needed to adjust from time to time. However the menu tree it was in had been removed leaving it a orphaned tree. So you couldn’t get to it through the ui. The only way to get to the setting was to go to a unrelated page in the documentation and click on the goto link in it. That would launch the menu that otherwise didn’t exist. From there you could back up and get into the menu to adjust the setting.