'readSync' does two different things - tells the OS we want to read some data and then waits for the data to be ready.

In a good API design, you should exposed functions that each do one thing and can easily be composed together. The 'readSync' function doesn't meet that requirement, so it's arguably not necessary - it would be better to expose two separate functions.

This was not a big issue when computers only had a single processor or if the OS relied on cooperative multi-threading to perform I/O. But these days the OS and disk can both run in parallel to your program so the requirement to block when you read is a design wart we shouldn't have to live with.

he was referring to fs.readSync (node) which has also has fs.read, which is async. there is also no parallelism in node.

i don't see it as very useful or elegant to integrate any form for parallelism or concurrency into every imaginable api. depends on context of course. but generalized, just no. if a kind of io takes a microsecond, why bother.

> tells the OS we want to read some data and then waits for the data to be ready

No, it tells the OS "schedule the current thread to wake up when the data read task is completed".

Having to implement that with other OS primitives is a) complex and error-prone, and b) not atomic.