A syscall is a method for calling a kernel routine to do something outside the current process. All i/o (network, filesystem, ipc), memory allocation, process

A syscall is a method for calling a kernel routine to do something outside the current process. All i/o (network, filesystem, ipc), memory allocation, process interaction, signals, etc go through syscalls. open(), read() and write() are all syscalls. If the syscall interface exists then the only thing left to do is to execute the program -- which depends on the cpu executing the machine instructions. If the machine instructions are for the wrong cpu then emulation may come into play.