Initialization files in the system are stored in the /etc/rc.d directory.
Linux slackware basically uses the BSD-style layout for its initialization files in
opposition to System V init scripts which makes changes in configurations enhancing difficulty without using a program designed.
In BSD-init scripts, each runlevel is given a single rc file. Whereas in the system V, each runlevel is given its directory which contains many init scripts which provides an organized structure easy to maintain. The categories of initialization files are system startup, runlevels, network initialization, and System V compatibility.