Basics of OS (Computer System)

Basics knowledge of computer system structure requires an understanding of how the operating system works.

 A computer consists of one or more CPUs and a large number of device controllers connected by a common bus that provides access to shared memory. 

Computer System Diagram


Key Terms -

1. Bootstrap program: it is the first program that runs after the power button clicks. Following are some of the main functions:

  • It stored in the ROM (Read-only Memory)
  • It must know how to load an OS and start executing the system
  • It must load and locate into an OS kernel.

Before we move on, we need to wonder what the OS kernel means. It's like the heart of an OS (Operating System). 

2. Interrupt: In general what is the meaning of Interrupt?  Let's say you have work and someone comes in and tells you to quit this work and do this work that I first assigned to you.  The same refers to computers. Assuming the CPU is doing that job, the hardware may interrupt immediately stops work, and transfers the execution to a fixed location.  When an event occurs, you can usually get a signal from hardware or software for interrupt. Hardware can anytime interrupt the CPU by sending a signal and is done using a system bus. After completion CPU resumes the interrupted computation.

3. System call: The above described how the hardware interrupts the CPU when it is interrupted by a software called a system call or monitor call.