Lecture 1 - Basics

Question 1

What is an operating system?

Answer 1

• Program that acts as intermediary between user and hardware
• Manages complexity of running multiple programs efficiently
• “Everything you don’t need to write to get a program to run”

Question 2

How did direct input operating systems work?

Answer 2

Run one job at a time:

enter into computer (possibly by rewiring)

Run

Get results

Question 3

What was the problem with direct input operating systems?

Answer 3

• Lots of wasted time - computer very often idle

Question 4

What is the point of the operating system?

Answer 4

Abstract details of hardware away so the programmer can focus on writing the program

Question 5

What is a batch system?

Answer 5

• Programmer prepares program away from machine (e.g. punch cards)
• Cards are read by card reader - input tape produced
• Input tape inserted on computer - Program is performed
• Output tape is produced

Question 6

What is spooling?

Answer 6

• Simultaneous peripheral operation on-line
• While one job is busy, perform I/O for another job
• Still only one job running but a bit more efficient

Question 7

What was the major hardware advance that helped move away from batch systems?

Answer 7

• 1960s - integrated circuits

Question 8

What is multiprogramming?

Answer 8

• Multiple jobs in memory - protected from one another
• Resources split - while one does I/O the other computes
• Still not interactive - user submits job, computer runs its, user gets results

Question 9

What is timesharing?

Answer 9

Like multiprogramming but timer device interrupts after given time

So perform one job for a bit, then the next, then the next, then back to the first etc.

Question 10

What does timesharing require?

Answer 10

CPU scheduling to choose next job to run

Question 11

What was Multics

Answer 11

• Joint industry/academe OS - supported hundreds of users on a computer roughly as powerful as intel 386

Question 12

What was Unix?

Answer 12

• OS inspired by Multics
• Written by Bell Labs in C

Question 13

What is the point of timesharing?

Answer 13

Allow multiple users to have jobs running on a computer at the same time

Question 14

What was Minix?

Answer 14

• Simplified version of UNIX that runs on a PC
• Intended for class teaching
• By Andrew Tanenbaum

Question 15

What is Linux?

Answer 15

By linus torvalds

Working from Minix, built his own kernel - encouraged people to contribute