SCANF返回值问题

返回值 a 表示成功地读到的数的个数。

输入字母，按整数格式%d读，失败了，所以a=0.

Both scanf and wscanf return the number of fields successfully converted and assigned; the return value does not include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned. The return value is EOF for an error or if the end-of-file character or the end-of-string character is encountered in the first attempt to read a character.

输入数字，匹配%d,配置b的值成功，scanf返回成功配置数量1；
输入字母，不匹配%d,配置b的值失败，scanf返回成功配置数量0；
输入Ctrl+Z，scanf返回-1；

scanf() printf()
返回值是这样定义的：
正常下：返回成功输入输出的变量个数
异常下：返回0