Understanding Computer I/O: Types, Transfer Methods, and Storage

Posted on Mar 19, 2025 in Computers

Understanding Computer I/O

Human-Readable I/O

  • Used for communication with the user
  • Printers
  • Graphical display terminals
  • Screen
  • Keyboard
  • Mouse

Machine-Readable I/O

  • Used for communication with electronic equipment
  • Units of discs and tapes
  • Sensors
  • Drivers
  • Activators

Communication I/O

  • Used to communicate with remote devices
  • Digital line drivers
  • Modem

Data Transfer Rate

  • There may be differences of several orders of magnitude between data transfer rates

Application

  • A disc used to store files requires software support for file management
  • A disc used as backing store for pages in a virtual memory scheme depends on the use of hardware and software virtual memory
  • A terminal used by a system administrator might have a higher priority

Complexity of Control

Transfer Unit

  • Data can be transferred as a stream of bytes or characters to a terminal or in larger blocks for a disk

Data Representation

  • Encoding Schemes

Error Conditions

  • The devices respond to errors differently

I/O Scheduling

  • The process makes a standby until the operation is complete before continuing

I/O Interrupt Driven

  • It emits a term of I/O
  • The processor continues executing instructions
  • The I/O module sends an interrupt when it has completed its work

DMA (Direct Memory Access)

  • A DMA module controls the exchange of data between main memory and an I/O module
  • The processor sends a request to transfer a data block to the DMA module and is interrupted only when the entire block has been transferred

Driver or Module I/O with Interruptions

  • The processor does not need to waste time waiting to undergo an operation of I/O

Direct Memory Access (DMA)

  • They move blocks of data to memory without involving the processor
  • The processor is involved at the beginning and end of the transfer, nothing more

Direct Memory Access (Direct Memory Access, DMA)

  • The processor delegates the operation of I/O to the DMA module
  • DMA module transfers the data directly from memory or to it
  • When the transfer is complete, the DMA module sends an interrupt signal to the processor

Buffers I/O

Reasons for this strategy

  • Processes must wait for completion of the operation of I/O prior
  • Some pages should remain in main memory during operation of I/O

Designed to Block

  • Stores information in fixed-sized blocks
  • The transfers are made from block to block
  • Used for disk and tape

Oriented Character Stream

  • Transfer information as a byte stream
  • Used for terminals, printers, communication ports, mouse and other pointing devices, and most devices that are not secondary storage

Albums
The following are the main advantages over the use of main memory and storage
• Many larger storage capacity.
· Lower price per bit.
§ The information is not lost when you shut down the computer.

Hardware For Albums
The discs are organized in cylinders, tracks, and sectors.

All sectors have an equal number of bytes.
The areas close to the edge of the disk will be physically larger than those near the ring.
A driver can search one or more units at once:
· They overlapping searches.
• While the software driver and expect to search a unit, the controller can initiate a search in another.
Many drivers can:
· Reading or writing a unit.
· Look elsewhere.