CS50

Question 1

what is the input to any computer?

Answer 1

elictiricity

Question 2

what does electricity represent in computers?

Answer 2

zeros and ones

Question 3

what is the highest you can count with 3 light bulbes?

Answer 3

up to 7 as we count from 0 and we have 8 patterns to count

Question 4

how did we count that 123 is one hundred and twenty 3?

Answer 4

because from the right to the left we use the base of 10
3 * 1 + 10^0
2 * 10 + 10^1
1 * 100 + = 10^2
123

Question 5

what is the base to calculate in binary systems?

Answer 5

2 ^ 0 1
2 ^1 2
2^ 2 4

Question 6

how to represent letters in binary?

Answer 6

we use numbers to represent each letter

Question 7

what is a byte?

Answer 7

8 bits

Question 8

what is a bit?

Answer 8

a zero or a one

Question 9

how many letters can u represent with a byte?

Answer 9

256

Question 10

what is an algorithm?

Answer 10

it’s a step by step instruction to solve a problem

Question 11

what is a compiler?

Answer 11

a software that converts source code to machine code?

Question 12

what is machine code?

Answer 12

it’s the language of zeros and ones

Question 13

how is the code evaluated?

Answer 13

from right to left

Question 14

how many bytes in an int?

Answer 14

4 bytes (32 bits)

Question 15

what is an unsigned integer?

Answer 15

it’s not a new data type it’s just a qualifier for int meaning it changes it’s properties containing only positive values

Question 16

how many bytes does char take?

Answer 16

1 byte (8 bits)

Question 17

how many bytes does a float take?

Answer 17

4 bytes (32 bits)

Question 18

how many bytes does a double take?

Answer 18

8 bytes (64 bits)

Question 19

when is && evaluates to true?

Answer 19

when all of the operands evaluate to true

Question 20

when is || evaluate to true?

Answer 20

when only one condition is true

Question 21

what happens when you don’t break in switch case?

Answer 21

u fall down the cases after one of them evaluates to true

Question 22

how many steps in compiling?

Answer 22

preprocessing:
copies functions prototypes any #include to current file
compiling:
converts source code to assembly code
assembling:
converts assembly code to machine code zeros and ones
linking:
links our zeros and ones to the original C language zeros and ones and other libraries

Question 23

what is an array?

Answer 23

a sequence of contiguous values stored back to back

Question 24

can u initialize an array with a variable?

Answer 24

no it must be a constant

Question 25

what is the null character?

Answer 25

\0 8 zero bits

Question 26

when can we describe an algorithm in theta?

Answer 26

if the upper bound is the same as the lower bound

Question 27

what is the complexity of linear search?

Answer 27

O(n)

sigma(1)

Question 28

what is psuedo code for linear search?

Answer 28

starting from first element till last
if we find element then exit
otherwise move to next element

Question 29

what is the main idea of binary search?

Answer 29

divide and conquer

each loop divide it by half

Question 30

what is the condition to do binary search?

Answer 30

elements must be sorted

Question 31

what is the complexity of binary search?

Answer 31

O(log n)

sigma (1)

Question 32

what is psuedo code for binary search?

Answer 32

repeat until subarray of size 0 (start and end are crossed)
calculate the current middle point of the current array if the target is at middle
or if the target is less than what’s at the middle, repeat but change the endpoint to be just the left of the middle
or if the target is more than what’s at the middle, repeat but change the start point to be just the right of the middle

Question 33

what is the main idea of bubble sort?

Answer 33

move higher elements to the right and lower value elements to the left

Question 34

what is psuedo code for bubble sort?

Answer 34

set swap counter to non-zero 
repeat until is swap counter not zero
set counter to zero
look at adjacent pairs
   if not in order swap them and increase counter by one

Question 35

what is the complexity of bubble sort?

Answer 35

O(n2)

sigma(n)

Question 36

what is the main idea of selection sort?

Answer 36

find the smallest element in an unsorted list and add it to the end of the sorted list

Question 37

what is psuedo code for selection sort?

Answer 37

repeat until no unsorted elements remain:
search the unsorted part of the data to find the smallest element
swap the smallest value with the first element of the unsorted part

Question 38

what is the complexity of selection sort?

Answer 38

O(n2)

simga(n2)