#include <stdio.h>
#include <string.h>
#define DENSITY 62.4
int main()
{
    float weight, volume;
    int size, letters;
    char name[40];

    printf("Hi!What's your first name?\n");
    scanf_s("%s", name);
    printf("%s,what's your weight in pounds?\n", name);
    scanf_s("%f", &weight);
    size = sizeof name;
    letters = strlen(name);
    volume = weight / DENSITY;
    printf("Well,%s,your volume is %2.2f cubic feet.\n",
        name, volume);
    printf("Also,your first name has %d letters,\n",
        letters);
    printf("and we have %d bytes to store it.\n", size);
    return 0;

}
运行后输入名字再回车，就开始出现问题了

比如:char d[20];写成scanf_s("%s",d,20);才是正确的