DOIO Call Format: Calling Procedures Quiz

Study Notes

I/O Request Format

A typical I/O request to the operating system has the format: DOIO(stream, mode, amount, destination, semaphore)
DOIO is the system I/O procedure name

I/O Request Parameters

Stream: the number of the stream on which I/O is to take place
Mode: indicates the operation required (e.g., data transfer or rewind) and character code to be used
Amount: the amount of data to be transferred (if applicable)
Destination (or source): the location for the data transfer
Semaphore: the address of a semaphore request to be signaled when the I/O operation is complete

Device Identification

The device corresponding to the specified stream is determined from the stream descriptor list of the calling process
The list is consulted at the time the stream was opened

Error Checking

The parameters of the I/O request are checked for consistency against the device descriptor information
If an error is detected, an exit can be made to the caller

I/O Request Processing

The I/O procedure assembles the request parameters into an I/O request block (IORB)
The IORB is added to a queue of similar blocks representing other requests for the same device
Requests in the queue may come from the same process or other processes (in the case of a shared device like a disk)

Description

Learn about the general form of a system I/O procedure call in operating systems, including the parameters like stream number, operation mode, data amount, destination, and semaphore. Understand how different aspects like data transfer and character codes are handled in this call format.