01-C-筆記

https://sandbox.cs50.io/
https://www.youtube.com/watch?v=e9Eds2Rc_x8

** clang **
source code -> complier -> machine code

int.c
cough1
agree
floats 溢位
mario 2

需引入參數

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

hello.c

#include <stdio.h>

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

$ clang hello.c
$ ./a.out 
$ clang -o hello hello.c
./hello

rm a.out 
yes

---

string.c

#include <stdio.h>

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

clang -o string string.c

string.c

step2.

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

// %s 意思是 string 

錯誤
$ clang string string.c -lcs50
clang-7: error: no such file or directory: ‘string’

正確

clang -o string string.c -lcs50

---

int.c

step3

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

int main(void)
{
    int age = get_int("What's your age?\n");
    int days = age * 365;
    printf("You are at least %i days old.\n", days);
}

make int
./int

---

float.c

step4

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

int main(void)
{
    int price = get_float("What's the price? \n");
    printf("Your total is %f. \n", price * 1.0625);
}

make float
./float

printf("Your total is %.2f. \n", price * 1.0625);
小數點後兩位

---

agree

step 5

// Logical operators

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

int main(void)
{
    // Prompt user to agree
    char c = get_char("Do you agree?\n");

    // Check whether agreed
    if(c == 'Y' || c == 'y')
    {
        printf("Agreed.\n");
    }
    else if(c == 'N' || c == 'n')
    {
        printf("Not agreed.\n");
    }
}
// Logical operators

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

int main(void)
{
    // Prompt user to agree
    char c = get_char("Do you agree?\n");

    // Check whether agreed
    if(c == 'Y' || c == 'y')
    {
        printf("Agreed.\n");
    }
    else if(c == 'N' || c == 'n')
    {
        printf("Not agreed.\n");
    }
}

make agree
./agree

---

cough1

step 6

#include <stdio.h>

void cough(void);

int main(void)
{
    for(int i=0; i < 3; i++) {
        // printf('Cough!');
        cough();
    }
}

void cough(void)
{
    printf("cough \n");
}

make cough1
./cough1

函數左側是輸出類型
void 是空
int 是自自
void cough(void)
{
printf(“cough \n”);
}

int get_positive_int(void)
{
int n;
do
{
n = get_int(“Positive Integer: “);

}
while(n < 1)
return n;

}

---

step7

mario 2

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

int main(void)
{
    int n;
    do
    {
        n = get_int("Width: ");
    }
    while (n < 1);
    for (int i =0; i < n; i++)
    {
        for(int j=0; j < n;  j++)
        <!-- 聖誕樹 for(int j=0; j < i;  j++) -->
        <!--  printf("#\n"); -->
        {
            printf("#");
        }
        printf("\n");
    }
    printf("\n");
}

$ make mario2
./mario2 
Width: 10
##########
##########
##########
##########
##########
##########
##########
##########
##########

step 9

floats 溢位

// 有限的內存 計算機 不能計算超過特定區域的值

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


int main(void)
{
    float x = get_float("x: ");
    float y = get_float("y: ");

    // printf("x/y = %f\n", x / y);
    printf("x/y = %.50f\n", x / y);
    
}

---

overflow

step10

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

int main(void)
{
    for (int i =1; ; i *=2)
    {
        printf("%i\n", i);
        sleep(1);
    }
}

make overflow
./overflow