02-Array-筆記

測驗
https://sandbox.cs50.io/
https://cs50.harvard.edu/x/2020/weeks/2/
https://www.youtube.com/watch?v=8PrOp9t0PyQ&t=11s

進入點

Source code :
https://cs50.harvard.edu/x/2020/psets/2/

Ｃ編譯過程

• precompiling 編譯前
• compiling 編譯
• assembling 組合
• linking

Source code

#include <cs50.h>
#include <stdio.h>
int main(void) 
{
    string answer = get_string("What's your name? \n");
    printf("hello, %s\n", answer);    
}

經過 precompiling

...
string get_string(string prompt)
int printf(string format , ...)
...
int main(void) 
{
    string answer = get_string("What's your name? \n");
    printf("hello, %s\n", answer);    
}

---

compiling 編譯發生的事情 會經過

1. intel AMD 大廠
2. CPU 處理基礎（底層操作）

   @main

   ...
   main :
       .cfi_startproc
   ##### BB#0:
       pushq  %rbp
   .Ltmp0:
       .cfi_def_cfa_offset16
   .Ltmp2:
       subq $16, $rsp
       xorl %eax, %eax
       movl %eax, edi

---

之後開始組合

assembling

011010101010110011010
101010101010101010101
101010101010101010101

---

linking

hello.c    cs50.c     pritf.c
01101010   0101010    0010101010

hello
010101010101010100100101001010
101010101010101010101010101101
````

若有問題發生
# linking
step 關注頂部
###  linking
buggy0.c

int main(void) {
printf(“hello word \n”)
}

make buggy0
// 會跳錯
help50 make buggy0


buggy1.c

#include <stdio.h>

int main(void) {
string_name = get_string(“what your name? \n”);
printf(“hello, %s”, name);
}

跳錯 
help50 make buggy1

buggc2.c

#include <stdio.h>

int main(void) {
for(int i =0; i<10; i++) {
printf(“#\n”);
}
}

./buggy2 


debug50: command not found 暫時跳過
影片 
1:12:39

-----------
複習
https://youtu.be/8PrOp9t0PyQ?t=5048

hello.c

#include <cs50.h>
#include <stdio.h>
int main(void)
{
char c1 = ‘H’;
char c2 = ‘I’;
char c3 = ‘!’;
printf(“%c %c %c\n”, c1, c2, c3);
printf(“%i %i %i\n”, c1, c2, c3);
}

terminal 操作

make hello
./hello

-----------------

#include <cs50.h>
#include <stdio.h>

int main(void) {
string s =get_string(“Input : “);
printf(“Output: “);

for(int i=0; s[i] != '\0'; i++) {
    printf("%c", s[i]);
}

printf("\n");

}

-------------
score3 

#include <cs50.h>
#include <stdio.h>

float average(int length, int array[]);

int main(void){
int n = get_int(“Scores : “);
int scores[n];

for(int i=0; i < n; n++) {
    scores[i] = get_int("Score %i", i + 1);
}
printf("Average: %.1f\n", average(n, scores));

}

float average(int length, int array[]) {
int sum =0;
for(int i =0; i <length; i++) {
sum += array[i];
}
return (float)sum / (float)length;
}

```