not for general use register - a register that has a purpose besides storing information, so don't touch it one of them is the RFLAGS register, that can for example be used to understand that a stack overflow has happened
RBP and RSP are used for stack manipulation, don't use them to store data
in order to make a syscall you need a kernel, but bootloaders don't have one for example, and they still work, so you can do functioning assembly code without syscalls.
not for general use register - a register that has a purpose besides storing information, so don't touch it
one of them is the RFLAGS register, that can for example be used to understand that a stack overflow has happened
RBP and RSP are used for stack manipulation, don't use them to store data
in order to make a syscall you need a kernel, but bootloaders don't have one for example, and they still work, so you can do functioning assembly code without syscalls.