# Datatypes --- # Review ---- ### What are datatypes? ---- ### int? ---- #### Finish last work! 1. Write a `C` code that makes 2 to the power of N(a static number) ```c= #include<stdio.h> int main(void){ int N = sizeof(int) * 8; int target = 2; /* * Your core codes should write here */ printf("%d\n", target); } ``` --- # Strings ---- ### How does strings store data ---- ## ASCII Codes ---- ##### ASCII Codes  ---- ### Any others? ---- ## How about Chinese Charactors? ---- ## Unicode ---- ### Unicodes  --- ### Test ---- #### ASCII Codes ```c= #include<stdio.h> int main(void){ printf("%d, %c\n", 'A', 'A'); } ``` ---- ##### Result ```shell= 65, A ``` ---- #### Wait ---- ##### What is `%d`, `%c`? ---- ##### Remember this?  [Reference](https://en.wikipedia.org/wiki/C_data_types) ---- ##### Tell the computer what kind of datatype it is - `%d` -> integer - `%c` -> charactor - `%s` -> string - `%f` -> float - and so on (just google it) [Reference](https://en.wikipedia.org/wiki/C_data_types) ---- ##### What happened? - 'A' = 65 in ASCII Code - 'A' and 65 are actually the same in binary, but different way to present - `%d` -> 65 - `%c` -> A ---- ##### Try it out! ```c= #include<stdio.h> int main(void){ printf("%d, %c\n", 'A', 'A'); printf("%d, %c\n", 65, 65); } ``` ###### result ```shell= 65, A 65, A ``` ---- ###### What is `\n`? ---- ##### Try it out! ---- ```c= #include<stdio.h> int main(void){ printf("%d", '\n'); } ``` ###### result ```shell= 10 ``` ---- ##### Compare to ASCII TABLE  LINE FEED (Enter) --- ### What else? ---- #### How many letters are there between 'A' and 'I'? ---- ABCDEFGHI -> 8 letters ---- #### Using Code? ---- #### Cool ```c= #include<stdio.h> int main(void){ printf("%d\n", 'I' - 'A'); } ``` --- #### Decode and Encode ---- #### ROT13 ROT13 ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet. ---- #### ROT13  ---- ```graphviz digraph { rankdir=LR; node [ shape=record ]; struct1 [ label = "<port1>Message"; ]; struct2 [ label = "{<port2>Non Sence}"; ]; struct3 [ label = "{<port3>Decode Message}" ] struct1:port1 -> struct2:port2 [ label="ROT13" ]; struct2:port2 -> struct3:port3 [ label="ROT13" ]; } ``` ---- #### Try to write a code to decode this! `LBHNERFBNJRFBZR` ---- #### How about this? `Lbh_ne3_f0_pb01!` ---- ##### Ans ```c= #include<stdio.h> #include<string.h> int main(void){ char input[100]; scanf("%s", input); for(int i = 0; i < strlen(input); i++){ if (input[i] >= 'a' && input[i] <= 'z'){ int tmp = input[i] - 'a'; tmp += 13; tmp %= 26; input[i] = tmp + 'a'; }else if (input[i] >= 'A' && input[i] <= 'Z'){ int tmp = input[i] - 'A'; tmp += 13; tmp %= 26; input[i] = tmp + 'A'; } } printf("%s\n", input); } ``` --- ### That's all for today ---- #### Any questions?