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CS50 2022 - Lecture 2 - Arrays.pptx
- 2. U I J T X B T D T 5 0
- 4. #include <stdio.h> int main(void) { printf("hello, worldn"); }
- 5. 01111111 01000101 01001100 01000110 00000010 00000001 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000010 00000000 00111110 00000000 00000001 00000000 00000000 00000000 10110000 00000101 01000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 11010000 00010011 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 00111000 00000000 00001001 00000000 01000000 00000000 00100100 00000000 00100001 00000000 00000110 00000000 00000000 00000000 00000101 00000000 00000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000 11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000 11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000 00001000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000011 00000000 00000000 00000000 00000100 00000000 00000000 00000000 00111000 00000010 00000000 00000000 00000000 00000000 00000000 00000000 ...
- 8. clang -o hello hello.c ./hello
- 9. #include <stdio.h> int main(void) { printf("hello, worldn"); }
- 10. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 11. clang -o hello hello.c -lcs50 ./hello
- 13. compiling
- 16. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 17. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 18. /usr/include
- 19. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 20. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 21. string get_string(string prompt); #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 22. string get_string(string prompt); #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 23. string get_string(string prompt); int printf(string format, ...); int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 24. ... string get_string(string prompt); int printf(string format, ...); ... int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 26. ... string get_string(string prompt); int printf(string format, ...); ... int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 27. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 28. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 29. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 31. ... main: # @main .cfi_startproc # BB#0: pushq %rbp .Ltmp0: .cfi_def_cfa_offset 16 .Ltmp1: .cfi_offset %rbp, -16 movq %rsp, %rbp .Ltmp2: .cfi_def_cfa_register %rbp subq $16, %rsp xorl %eax, %eax movl %eax, %edi movabsq $.L.str, %rsi movb $0, %al callq get_string movabsq $.L.str.1, %rdi movq %rax, -8(%rbp) movq -8(%rbp), %rsi movb $0, %al callq printf ...
- 34. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 35. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 36. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 37. #include <cs50.h> #include <stdio.h> int main(void) { string name = get_string("What's your name? "); printf("hello, %sn", name); }
- 38. hello.c
- 39. hello.c cs50.c
- 46. compiling
- 47. decompiling
- 50. debugging
- 56. printf
- 57. printf debugger
- 70. representation
- 71. types
- 73. bool 1 byte int 4 bytes long 8 bytes float 4 bytes double 8 bytes char 1 byte string ? bytes ...
- 85. int score1 = 72; int score2 = 73; int score3 = 33;
- 87. 72 score1
- 91. int score1 = 72; int score2 = 73; int score3 = 33;
- 92. arrays
- 93. int scores[3];
- 94. int scores[3]; scores[0] = 72; scores[1] = 73; scores[2] = 33;
- 96. arguments
- 97. char c1 = 'H'; char c2 = 'I'; char c3 = '!';
- 99. H c1 I c2 ! c3
- 100. 72 c1 73 c2 33 c3
- 102. string
- 103. string s = "HI!";
- 105. H I s !
- 106. H s[0] I s[1] ! s[2]
- 109. H s I ! 0
- 110. NUL
- 113. string s = "HI!"; string t = "BYE!";
- 115. H s I ! 0
- 116. H s I ! 0 B t Y E ! 0
- 118. string words[2]; words[0] = "HI!"; words[1] = "BYE!";
- 119. H words[0] I ! 0 B words[1] Y E ! 0
- 121. string
- 122. string.h
- 124. strlen
- 125. ctype.h
- 130. #include <stdio.h> int main(int argc, string argv[]) { ... }
- 131. cowsay
- 132. exit status
- 135. #include <stdio.h> int main(int argc, string argv[]) { ... }
- 136. #include <stdio.h> int main(int argc, string argv[]) { ... }
- 138. echo $?
- 139. cryptography
- 140. encryption
- 141. input → → output
- 142. plaintext → → ciphertext
- 143. plaintext → → ciphertext cipher
- 144. cipher plaintext → → ciphertext key →
- 145. HI! → 1 →
- 146. HI! → → IJ! 1 →
- 147. decryption
- 148. UIJT XBT DT50 → -1 →
- 149. U I J T X B T D T 5 0
- 150. T I J T X B T D T 5 0
- 151. T H J T X B T D T 5 0
- 152. T H I T X B T D T 5 0
- 153. T H I S X B T D T 5 0
- 154. T H I S W B T D T 5 0
- 155. T H I S W A T D T 5 0
- 156. T H I S W A S D T 5 0
- 157. T H I S W A S C T 5 0
- 158. T H I S W A S C S 5 0
Editor's Notes
- Reload codespace Uncheck VS Code tabs
- Reload codespace Uncheck VS Code tabs
- know it doesn't feel like it, but have had training wheels on… bottom-up understanding, to deduce solutions to problems
- hello0.c
- hello1.c
- ls
- 0s and 1s for printf.c are actually those for libc.so.
- intellectual property
- easier with hello-world than with, e.g., loops, which could be for loops or while loops, etc.
- https://en.wikipedia.org/wiki/Software_bug https://en.wikipedia.org/wiki/Harvard_Mark_II Dr Grace Hopper, Yale Mark II
- https://en.wikipedia.org/wiki/Grace_Hopper
- https://www.britannica.com/technology/Harvard-Mark-I SEC
- buggy0.c
- buggy1.c
- "explain as though to a TA, and when you hear yourself saying something that doesn't make sense…"
- La Parguera - Lajas, PR
- La Parguera - Lajas, PR
- largest radio telescope in the Northern/Western Hemisphere- National Astronomy and Ionosphere Center (Arecibo Observatory)
- San Francisco
- San Francisco sea lions
- Stanford
- Rome
- Rome
- London
- https://www.youtube.com/watch?v=cZB_EBsnc8c
- scores0.c
- not best design
- scores{1,2,3}.c should use constant for 3
- scores4.c
- hi{0,1}.c what about chars?
- most types have fixed length, so how implement strings?
- hi2.c
- How know where end is?
- hi3.c
- hi4.c
- https://asciichart.com/
- https://asciichart.com/
- hi5.c
- hi6.c
- hi7.c
- length{0,1}.c
- length2.c string{0,1}.c
- uppercase{0,1,2}.c
- make, cd, etc.
- greet{0,1,2,3}.c
- cowsay moo cowsay -f duck quack cowsay -f dragon RAWR
- https://community.zoom.com/t5/Meetings/ERROR-1132/td-p/40521
- https://github.com/
- status.c
- https://emojipedia.org/tangerine/