I think it's in contrast to "reactive IO". Roughly: When you want to read from files reactively, you run "select" with these files as arguments in a loop. The

I think it's in contrast to "reactive IO". Roughly: When you want to read from files reactively, you run "select" with these files as arguments in a loop. The return value will tell you, which file is ready to be read. In proactive IO, you instead supply a buffer to the read operation and get a handle back, that will notify you when the read operation is finished. Windows IO Completion Ports (IOCPs) are an example of this.