system call

Hi, I want to implement a system call as explained in Linux kernel development by Robert Love. He does three things adding entry to entry.S adding entry to asm/unistd.h and adding the system call code to sched.c and then make + make install I do not want to implement for all architectures but only for my PC which is 64 bit. I am not able to locate files entry. S and unistd.h which he is telling in his tutorial. Please help me out to figure out the exact steps. Please also mention the linux kernel version I should use. Nitin