为什么用int型变量去存放字符比如,getchar()接收char字符,但返回值是int再比如,《The C Programming Language》中,(2.7节)将大写字符转换成小写的lower()函数
/*lower: convert c to lower case;ASCII only*/int lower(int c){ if(c>='A'&&c<='Z') return c+'a'-'A'; else return c;}