Why learn about OS?
- Security: Creating a protected environment to run programs
- To have an understanding of how computers work: A modern computer and how we use it is defined the OS (the abstractions, how systems work)
- Applications and Portability
- Reliability: understanding of lots of hardware and software mechanisms that make computer systems hard to crash
- Files and Program Management
- To explore
Fundamentals of Computer Systems
Basic computer components: CPU (basic operation: fetch, decode and execute), Memory (Von Neumann Model of Computing: Everything including the instructions are in some store), Disk (being increasingly replaced by solid state storage, nowadays though both are still being used), mouse, keyboard, display, network
What is OS?
- OS provides the abstraction of having as many virtual CPUs: For the purpose of efficieny (better utilization of resources/hardware) and multi-tasking (not limited by the physical hardware, ease of use)
- OS gives an illusion of a memory that is private to your program: For the purpose of security (not writing on someone else’s memory; virtual memory)
- In UNIX file systems, write operations first buffer the values on memory for 30 seconds or so before flushing it to the hard drive/SSD (cause this operation is slow). But we can use the “fsync()” interface to force the operation on the disk.
- trace (can be created using a kernel tracing tool): shows how many functions inside the kernel were called during the execution of a program
- For file systems: how do we function in-terms of committing data to the disk and reading data from the disk
- Threads: allow functions inside the same program to run at the same time (can be created using Pthread_create in C), its also known as multi-threaded or concurrent program (useful in running parallel programs and building web servers)
Accessing shared data results in different values every time execution of a program occurs (due to race conditions — fundamental problem in concurrency). To solve this we can use locks (which makes the program slower — cost of correctness)
GRATITUDE: I would love to thank Professor Remzi Arpaci-Dusseau for such an amazing content; as I was inspired to learn more and blog on Operating Systems due to your online lectures. I enjoyed every minute of your lecture as well as your marvelous sense of humor.