Parts of the OS specification which does not fit into other sections of this documentation has been collected here. These topics are internal to the operating system, but part of the OS specification. Some of these details are hidden from application/system programs and have more hardware dependency than most other parts of this documentation.

When the machine is powered on, the system is configured to start executing a ROM code in privileged mode. This code is called the bootstrap loader. This ROM code loads the first block of the disk into a pre-defined area in memory and transfers control to the newly loaded code. This code is called the OS startup code.

The OS startup code loads the system call routines into memory. These routines are loaded as software interrupt handlers. In addition to these, there are four hardware interrupt / exception handler modules that are to be loaded - the timer interrupt handler, the exception handler, the disk interrupt handler and the terminal handler. If the architecture supports other devices, then the corresponding device interrupt handlers also must be loaded by the OS Startup code. This specification leaves out details regarding other device handlers.