1. External Devices
1.1. Human Readable
1.1.1. Suitable to communicate with computer user
1.1.2. Eg ; Printers
1.2. Machine Readable
1.2.1. Suitable to communicate with equipment
1.2.2. Eg ; Magnetic disks
1.3. Communication
1.3.1. Suitable to ocmmunicate with remote devices
1.3.2. Eg ; Human/Machine Readable
2. Modules
2.1. Control & Timing
2.1.1. To coordinate flow of traffic between internal resources and external device
2.2. Processor Communication
2.2.1. Command decoding
2.2.1.1. I/O module accepts commands from processor
2.2.2. Data
2.2.2.1. Exchanged data between processor and I/O Modules via data bus
2.2.3. Status Reporting
2.2.3.1. Peripherals is slow so its important to know the status
2.2.4. Address recognition
2.2.4.1. I/O modules must recognize one unique address for each peripheral
2.3. Device Communication
2.3.1. Command
2.3.2. Statuts Info
2.3.3. Data
2.4. Data Buffering
2.4.1. Data are buffered in I/O module and sent to peripheral devices at its data rate
2.5. Error
2.5.1. Mechanical & Electrical Malfunctions
2.5.2. Unintentional Changes
2.5.3. Transmission
3. Direct Memory Access
3.1. A way for I/O Devices to bypass CPU when accessing memory
4. Interface To External
4.1. Control SIgnal
4.1.1. Determines the function that device will perform
4.2. Data Signal
4.2.1. Send or receive data from I/O module in form of bits
4.3. Status Signal
4.3.1. Indicates the status of signal
5. I/O Issues
5.1. Wide variety of peripherals
5.2. Data Transfer Rate is slower than memory/processor
5.3. Data Transfer Rate is faster than memory/processor
5.4. Peripherals use different data formats
6. I/O Module
6.1. Functions
6.1.1. Interface to processor & memory via system bus / central switch
6.1.2. Interface to or more peripheral devices