的asyncio样品（也叫“PDC”样本）是一个字符

代码说明：

The AsyncIO sample (also called the "PDC" sample) is a character-mode program for searching the files in a directory tree for a match against a pattern. It uses multiple threads, with each thread processing one file at a time, accumulating its matches. When each thread finishes searching a file, the thread sends the matches contiguously to a standard output.