Introduction

Hardware should support certain features to run OS properly!

I/O

• I/O devices and CPU can execute concurrently
• Each device controller is in charge of a particular device type
• Each device has a local buffer
• CPU issues specific commands to I/O devices
• CPU moves data between main memory and local buffers

Problem: I/O is too slow (sometimes, its time is unknown e.g. keyboards)
CPU is a precious resource, it should be freed from time-consuming tasks!

수치적인 근

방정식의 근은 오차범위 내에서만 파악 가능
ex) $10x = 3$의 정확한 근을 표현할 수 없음

따라서 방정식의 근을 찾는다는건 사실 $|f(x)| < \varepsilon$이 되는 값의 범위을 찾는다고 생각해야 함.
실수를 다룰 때는 정확하게 a==b인지 검사할 수 없다!!

이분법

$f(x)$가 연속함수고 $f(a)f(b) < 0$이라면 $f(x)=0$인 $x \in (a,b)$가 존재한다.

정수

다 알다시피 $2n$비트 숫자는 $-2^n$ 부터 $2^n - 1$ 까지 표현가능

실수

$$x = \pm 1.m \times 2^c$$

단정도 (single)에선 sign 1비트, exponent 8비트, mantissa 23비트
배정도는 (double)에선 sign 1비트, exponent 11비트, mantissa에 52비트

Why OS?

To protect and to serve (from NYPD)

Operating System (kernel) is a software that converts hardware into a useful form for applications.
Middleware, Software Development Environment (compilers, loaders, editors, libraries, ...) are not OS!

History of OS

1G (1945 ~ 1955)

Cryptography

1. 1G: Classical Cryptography
   (Oxford) The art of writing or solving "codes"
   Is wasn't even called cryptography...
2. 2G: Modern Cryptography
   Research has been active enough to establish cryptography since the 1970s
3. 3G: Advanced Cryptography The real "modern cryptography"

The book only focus on 1970s modern cryptography... But we will learn some advanced cryptography too.

What is cryptography?

Not cryptocurrency

Introduction

https://arxiv.org/abs/1706.03762

Vaswani, A., Shazeer, N., Parmar, N., Uszkoreit, J., Jones, L., Gomez, A. N., ... & Polosukhin, I. (2017). Attention is all you need. Advances in neural information processing systems, 30.

일명 Transformer 논문. LLM 시대를 열 수 있게 만들어준 기념비적인 논문이다.

Background

Dynamics

Simulation is the most popular method to create computer animation procedurally.

Unlike kinematics, dynamics concerns forces and their effect on motion.

Animation Equation

The basic equation: $F=ma$??

4G/5G cellular networks

The solution for wide-area mobile internet!
We have more mobile-broadband-connected devices than fixed-broadband-connected devices.

Widespread deployment/use!
4G is available 97% of the time in Korea!

Comparison with wired internet

Similarities:

History of Animation

Ancient Egypt, Leonardo da Vinci, ...
Lots of people drew movement as a series of frame!

Phenakistoscope: Draw frames on the disk, then spin it to animate it!
In fact we have a 3D version of phenakistoscope, called zoetrope!

The first film captured movement of the horse!
Multiple cameras were placed in the path of the horse.
In fact this was only a set of photos, not a real animation.

The first animation on film was made by hand!
Photos of chalkboard drawing were taken and animated. (about 15 min)

Wireless and mobile networks

• More wireless (mobile) phone subscribers than fixed (wired) phone subscribers!
• More mobile-broadband-connected devices than fixed-broadband-connected devices.

Two important challenges:

• Wireless: Communication over wirelss link.
• Mobility: Handling the mobile user who changes point of attachment to network.

Elements of a wireless network