CS50-01-Scratch: 01-Getting started with Data Representation

Day 1 of CS50's Introduction to Computer Science here I noted keypoints of the very first part of the course how to represent Data and how computer interprets it

Computer Science

• Computer science is used to solve problems with some techniques and methods.

• With the help of computational thinking, we can think like a computer to solve problems using algorithms.

• In algorithms, we can input data and design algorithms to solve specific problems and give solutions as output

Binary system

• By far we can count 31 numbers by hand

• The computer is an electro-mechanical device that requires electricity to operate

• The state where electric current is there is 1 and is not is 0.

• In decimal, we can count each digit as in number multiplied by the power of 10 similarly, we can represent digits in the power of 2

  ex - 123 -> 1x10^2 + 2x10^1 + 3x10^0 -> 100 + 20 + 3 == 123

  binary -> 4 -> 100 -> 1x2^2 + 0x2^1 + 0x2^0 == 4 + 0 + 0 => 4 -> 100

  • Bit -> One bit represents 0 or 1

  • Byte -> Collection of 8 bits -> 2^8 -> 25611 numbers can be presented from range 0-255

  • For negative 8th bit represents the negative number if 0 -> positive and 1 -> negative

  • so the range of is (2^(n-1) - 2^(n-1)-1) i.e. (-128 to 127)

ASCII and Unicode representation

• Ascii code is the human convention to represent each alphabet and symbol as a number

• Unicode is a superset of ASCII which not only relies on 8 bits but also can use 16 or 24 sometimes even 32 bits if required per character which enables us to use roughly 4 billion characters

• This leads to a large no of calculations so in Unicode we use the hexadecimal number system

• so for example in the yellow thumbs-up emoji, we use (👍) U+1F44D as Unicode, so for another skin tone we don't change the emoji Unicode instead we add the color cod like U+1F44D U+1F3FD (👍🏿)

• Same for couple love we have the same Unicode we just add code accordingly like man-woman, man-man, women-women, etc.

• Ex-(🧑🏻‍❤️‍🧑🏽💑) Unicode for heart and man will be the same and code gets added to it when we change color or man to women. U+.... U+200D U+.... U+200D U+....

• Here U+200D is zero-width-joiners which joins two emojis to each other

Colors

• RGB is used to associate colors, each pixel has these three numbers and every color is possible by their combination

Representation of certain meaning

• As we know RGB(73,72,33) gives us light yellow but in the text it gives us Hi! and different in the case of numbers

• So to interpret it correctly one should set important context