CS basics

Question 1

What does big O notation do?

Answer 1

Describe performance of an algorithm, meaning the cost in relation to input

Question 2

Big O O(1)

Answer 2

Constant time (eg printing the first item in array)

Question 3

Big O O(n)

Answer 3

Linear time - grows 1:1 with growth of input (eg printing all items in array)

Question 4

Big O O(n2)

Answer 4

Quadratic time (eg nested loops)

Question 5

Big O O(log n)

Answer 5

Logaritmic time (binary search, very scaleable)

Question 6

Big O O(2n)

Answer 6

Exponential time (avoid at all cost)

Question 7

Arity

Answer 7

Antal argument i en funktion

Question 8

Interpreters translate…

Answer 8

Line by line

Question 9

Compilers translate…

Answer 9

All lines and execute the whole program

Question 10

Vad är HMR (Hot Module Replacement) ?

Answer 10

En funktion som tillåter snabbare iterationer genom att ersätta, lägga till eller ta bort moduler i en applikation utan att behöva ladda om hela sidan eller förlora tillstånd.

Question 11

What does ‘binary’ mean?

Answer 11

‘Of two states’ eg on/off or 1/0

Question 12

How big is one binary number?

Answer 12

1 bit

Question 13

How many values can be represented with 8-bit numbers?

Answer 13

0 -255 (256)

Question 14

How big is 8 bits?

Answer 14

1 byte

Question 15

How many values can be represented with 32 bits?

Answer 15

Just under 4.3 billion

Question 16

How are numbers used to represent letters in binary?

Answer 16

UTF (8 or 16)

Question 17

Where do computers calculate?

Answer 17

In the ALU

Question 18

ALU

Answer 18

Arithmetic and Logic Unit

Question 19

UTF

Answer 19

Unicode Transformation Format

Question 20

How are values stored in memory?

Answer 20

Registers & RAM

Question 21

RAM

Answer 21

Random Access Memory

Question 22

How long does a value stay in RAM?

Answer 22

As long as the power stays on (or it isn’t needed anymore)

Question 23

CPU

Answer 23

Central processing unit

Question 24

What does the CPU do?

Answer 24

Executes programs, ie series or collections of instructions

Question 25

How does the CPU execute programs?

Answer 25

Via Fetch/decode/execute cycle

Question 26

What is clock speed?

Answer 26

How fast a CPU can perform one fetch/decode/execute cycle

Question 27

What unit is clock speed measured in?

Answer 27

Gigahertz, billions of CPU-cycles every second.

Question 28

What's the small piece of RAM installed on the CPU called?

Answer 28

Cache

Question 29

Why do we need a cache?

Answer 29

Because data needs to travel between CPU and RAM it's faster to check first if we already have the value stored in cache.

Question 30

Cache hit

Answer 30

Data found in cache

Question 31

Cache miss

Answer 31

Data **not** found in cache

Question 32

What can multi-core processors do?

Answer 32

Run multiple streams of instructions at once - but sharing cache for example so the cores can work together

Question 33

What is the native language of computers?

Answer 33

Raw binary.

Question 34

What do assemblers do?

Answer 34

Read instructions written in assembly code and translate them to binary.

Question 35

What are assembly languages?

Answer 35

Low level programming languages that map 1:1 to machine instructions.

Question 36

High level languages are fed through ...

Answer 36

A compiler

Question 37

What are the three parts of computer science?

Answer 37

1. Theoretical computer science 2. Computer engineering 3. Applications/software engineering

Question 38

What is the stack?

Answer 38

Short-term memory for currently executing functions. Gets overwritten all the time.

Question 39

What's the heap?

Answer 39

Long-term memory, needs to be allocated and freed or your program will have a memory leak and start running very slow.

Question 40

Stack and/or heap overflow?

Answer 40

Too much memory is used and the stack and the heap start clashing.

Question 41

What can cause stack overflow?

Answer 41

Infinte loops, recursive calls.

Question 42

What's the first thing that happens when we type in a url in the browser?

Answer 42

Request is sent to ISP - ISP asks DNS what IP to go to.

Question 43

ISP

Answer 43

Internet Service Provider

Question 44

What happens when ISP ask DNS about IP address?

Answer 44

IP address is sent to ISP and returned to browser.

Question 45

What happens when IP address is returned from DNS to ISP to browser?

Answer 45

Browser sends request to the IP address directly

Question 46

What happens when the browser sends request to IP address?

Answer 46

Server at IP address either rejects or responds and sends html, css and js files

Question 47

What happens when the browser recieves a server response?

Answer 47

The browser renders the page.

Question 48

What is the Internet backbone?

Answer 48

Physical cables all over the world

Question 49

Three basic ways to improve web performance?

Answer 49

1. Make sure physical distance from servers is small 2. As few trips as possible 3. As small files as possible

Question 50

What is WWW?

Answer 50

A shared language between computers that works on top of the internet.

Question 51

What are 5 expectations of a junior developer?

Answer 51

1. Know the basic stack 2. Basic git 3. Actively seeking to learn 4. Persistent with problem solving 5. Never afraid to ask questions -nothing is dumb

Question 52

"Your code will always ... , may as well ..."

Answer 52

"Your code will always **suck**, may as well **have fun**"

Question 53

"You will never ..., but that's ok"

Answer 53

"You will never **know enough**, but that's ok"

Question 54

"You will never be a master but..."

Answer 54

"You will never be a master but being a student is so much better"

Question 55

QDD

Answer 55

Question Driven Development