Post on 08-Feb-2021
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