rust-kernel | A toy kernel in rust | Interpreter library

I'd like to explain zx485's comment in more detail:

I've often seen that assembly language beginners are confused about what instructions like int (x86), syscall (MIPS) or SWI (ARM) actually do.

Actually, these instructions are a special form of call instruction: They call some sub-routine which is typically located in the operating system.

64-bit x86 CPUs have different operating modes. One of them is named "real mode". In this mode the CPU can only execute 16-bit code.

The BIOS sub-routine that can be called using int 0x16 only works when the PC is operating in "real mode".

The fact that your program is a 64-bit program (registers like rax are used) tells us that your CPU is not running in real mode.

If you are writing your own operating system, you can define own sub-routines that are called by certain int instructions:

You can define a sub-routine that is called by int 0x16 which reads the keyboard and another one called by int 0x10 writing to the screen.

However, you are also free to define that int 0x16 is used for writing to the screen and int 0x10 is used for hard disk access in your operating system.

And in every case you'll have to write the sub-routines yourself because the existing sub-routines in the BIOS cannot be used in any other operating mode than "real mode". (This is what Ross Ridge is indicating in his comment.)