[C/C++--ERROR]: The scanf_s function requires 2 parameters (name, character length) to obtain an array

1. Code: talkback.c - demo and user interaction

// talkback.c -- 演示与用户交互
#include <stdio.h>
#include <string.h>  // 提供strlen()函数的原型
#define DENSITY 62.4 // 人体密度（单位：磅/立方英尺）
int main(void) {
    
    
	float weight, volume;
	int size, letters;
	char name[40];  //name是一个可容纳40个字符的数组

	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;
}

2. The error is as follows:

The following warning will appear at compile time, and the subsequent code of scanf_s cannot be run at runtime:

1>e:\talkback.c(17): warning C4244: “=”: 从“double”转换到“float”，可能丢失数据
1>e:\talkback.c(11): warning C4473: “scanf_s”: 没有为格式字符串传递足够的参数
1>e:\talkback.c(11): note: 占位符和其参数预计 2 可变参数，但提供的却是 1 参数
1>e:\talkback.c(11): note: 缺失的可变参数 2 为格式字符串“%s”所需
1>e:\talkback.c(11): note: 此参数用作缓冲区大小

3. Reason analysis:

According to the above warning, the scanf_s call is missing one parameter (not passing enough parameters), scanf_s is a safe version of scanf and requires a parameter indicating the length of the array, so the correct call should be:

scanf_s("%s", name, 40);

4. Complete code:

// talkback.c -- 演示与用户交互
#include <stdio.h>
#include <string.h>  // 提供strlen()函数的原型
#define DENSITY 62.4 // 人体密度（单位：磅/立方英尺）
int main(void) {
    
    
	float weight, volume;
	int size, letters;
	char name[40];  //name是一个可容纳40个字符的数组

	printf("Hi, What's your first name?\n");
	scanf_s("%s", name, 40);
	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;
}