一些有用的C语言小程序：输入以秒为单位所表示的时间，试将其换算为几日几时几分几秒；输入一个华氏温度，输出对应的摄氏温度，要求输出结果保留两位小数；输出a、b两数中的较大值；输入一个年号，判断该年是否闰年，并输出判断结果；求一元二次方程的根，系数a、b、c由键盘输入-Some useful C-applet: input in seconds the time indicated, try to convert a fraction to a few days when a few seconds　enter a Fahrenheit temperature, the output corresponds to the Celsius temperature, required to retain two decimal output　output a, b the number of the larger of two values　enter an era name, determine whether a leap year that year, and output to judge the results　seek the root of quadratic equation, coefficients a, b, c from the keyboard