This is CS50

This is CS50

2/3of CS50 students have never taken CS before

what ultimately matters in this course is not so much where you end up relative to your classmates but where you end up relative to yourself when you began

input → → output

representation

decimal

base-10

0 1 2 3 4 5 6 7 8 9

0 1

base-2

binary

0 1

bits

0

1

0 1

0 1 2 3 4 5 6 7 8 9

123

1231

12310 1

123100 10 1

123100 10 1

100 × 1

123100 10 1

100 × 1 10 × 2+

123100 10 1

100 × 1 10 × 2 1 × 3+ +

123100 10 1

100 20 3+ +

123

# # #100 10 1

# # #102 101 100

# # #22 21 20

# # #4 2 1

0004 2 1

0014 2 1

0104 2 1

0114 2 1

1004 2 1

1014 2 1

1104 2 1

1114 2 1

This is CS50

A

65

01000001

ASCII

... A B C D E F G H I ...

... 65 66 67 68 69 70 71 72 73 ...

72 73 33

H I

72 73 33

H I !

72 73 33

H I !

01001000 01001001 00100001

bytes

Unicode

128514

000000011111011000000010

RGB

72 73 33

72 73 33

http://www.youtube.com/watch?v=sz78_07Xg-U

input → → output

algorithms

This is CS50

+1-949-468-2750

http://www.youtube.com/watch?v=-yTRajiUi5s

http://www.youtube.com/watch?v=F5LZhsekEBc

n

n/2n

n/2n

n/2n

n/2n

n/2n

n/2n

log2 n

pseudocode

1 Pick up phone book2 Open to middle of phone book3 Look at page4 If person is on page5 Call person6 Else if person is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if person is later in book10 Open to middle of right half of book11 Go back to line 312 Else13 Quit

1 Pick up phone book2 Open to middle of phone book3 Look at page4 If person is on page5 Call person6 Else if person is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if person is later in book10 Open to middle of right half of book11 Go back to line 312 Else13 Quit

1 Pick up phone book2 Open to middle of phone book3 Look at page4 If person is on page5 Call person6 Else if person is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if person is later in book10 Open to middle of right half of book11 Go back to line 312 Else13 Quit

1 Pick up phone book2 Open to middle of phone book3 Look at page4 If person is on page5 Call person6 Else if person is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if person is later in book10 Open to middle of right half of book11 Go back to line 312 Else13 Quit

1 Pick up phone book2 Open to middle of phone book3 Look at page4 If person is on page5 Call person6 Else if person is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if person is later in book10 Open to middle of right half of book11 Go back to line 312 Else13 Quit

● functions● conditions● Boolean expressions● loops

● functions● conditions● Boolean expressions● loops● variables● threads● events● ...

#include

int main(void){ printf("hello, world\n");}

input → → outputalgorithms

→ → algorithms → output

→ → → output

→ →

input → → outputalgorithms

→ → → outputalgorithms

→ → → output

→ →

input → → outputalgorithms

→ → → outputalgorithms

→ → → output

→ →

→

→

→ →

→ → →

abstraction

This is CS50