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

0 1 2 3 4 5 6 7 8 9

0 1

123

1231

12310 1

123100 10 1

123100 10 1

100 × 1

123100 10 1

100 × 1 +

123100 10 1

100 × 1 10 × 2+

123100 10 1

100 × 1 10 × 2+ +

123100 10 1

100 × 1 10 × 2 1 × 3+ +

123100 10 1

100 20 3+ +

123

000100 10 1

001100 10 1

002100 10 1

003100 10 1

004100 10 1

005100 10 1

006100 10 1

007100 10 1

008100 10 1

009100 10 1

010100 10 1

000100 10 1

000102 101 100

00022 21 20

0004 2 1

0014 2 1

0104 2 1

0114 2 1

1004 2 1

1014 2 1

1104 2 1

1114 2 1

bit

💡

bit bit bit bit bit bit bit bit

💡💡💡💡💡💡💡💡

byte

💡💡💡💡💡💡💡💡

A

65

01000001

65

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

Unicode

128514

11111011000000010

RGB

72 73 33

72 73 33

input → → output

algorithms

10245122561286432168421

pseudocode

1 Pick up phone book2 Open to middle of phone book3 Look at page4 If Smith is on page5 Call Mike6 Else if Smith is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if Smith 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 Smith is on page5 Call Mike6 Else if Smith is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if Smith 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 Smith is on page5 Call Mike6 Else if Smith is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if Smith 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 Smith is on page5 Call Mike6 Else if Smith is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if Smith 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 Smith is on page5 Call Mike6 Else if Smith is earlier in book7 Open to middle of left half of book8 Go back to line 39 Else if Smith 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 <stdio.h>

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

input → → outputalgorithms

→ → algorithms → output

→ → → output

→ →

input → → outputalgorithms

→ → → outputalgorithms

→ → → output

→ →

input → → outputalgorithms

→ → → outputalgorithms

→ → → output

→ →

→

→

→ →

→ → →

This is CS50