#include <stdio.h>
void main()
{
    float tran(float);
    float c,x;
    scanf("%f", &c);
    x = tran(c);
    printf("%6.1f^F = %6.1f^C", c, x);
}

float tran(float a)

{
    return(5.0 / 9.0)*(a - 32.0);
}
说程序在scanf有问题

1>------ 已启动生成:  项目: ConsoleApplication2, 配置: Debug Win32 ------
1>  源.cpp
1>c:\users\administrator\documents\visual studio 2013\projects\consoleapplication2\consoleapplication2\源.cpp(6): error C4996: 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.
1>          d:\vc2013\vc\include\stdio.h(283) : 参见“scanf”的声明
1>c:\users\administrator\documents\visual studio 2013\projects\consoleapplication2\consoleapplication2\源.cpp(14): warning C4244: “return”: 从“double”转换到“float”，可能丢失数据
========== 生成:  成功 0 个，失败 1 个，最新 0 个，跳过 0 个 ==========



每次出现这句话       error C4996: 'scanf': This function or variable may be unsafe. Consider using scanf_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS. See online help for details.


我用的是vs2013

哦，我知道了，每次出现明显错误才仔细看，遇到这种警告就没在意。。可是为什么会不安全啊

多谢1