Schedule processes when the hardware timer ticks

[howardlau1999]

The very first step towards a working minimal operating system is the ability to do some initialization work after booting up and handle interrupts where it can have a chance to schedule and switch processes.

To achieve this, we should

• Write the entry function which does all the initialization work including initializing necessary data structures and setting up interrupt handler
• Define a minimal structure of PCB(Process Control Block)
• Implement the context switch function
• Implement a very basic scheduler
• Call the scheduler and switch to target process when the hardware timer ticks