Four
Your standard computer has two IDE channels, each can support up to two devices for a total of 4 IDE devices.
With additional IDE controllers, it is possible to have 8 12 or even 16 IDE devices on a system, but this is fairly uncommon.
Four computers and two phone devices can be connected with that.
A device which connects to the computer is called a "peripheral."
2
2 devices
In a plain SCSI (Small Computer System Interface) chain, up to 8 devices can be connected, including the SCSI host adapter. This means there are 7 additional devices that can be connected to the chain. SCSI IDs range from 0 to 7, with each device needing a unique ID for proper communication.
I read by 2012, 17 billion devices will be connected to the internet
USB connectors are used to connect peripheral devices such as printers, cameras and keyboards to a computer. The USB port is a technology standard developed in the 1990s that makes it possible to plug and play many different devices on the same computer system.
16 devices can be connected
Keyboard and touchpad are input devices, but they have output aspects, such as the CAPS LOCK light indicator on a standard PC keyboard. Typical output devices on a standard computer include the video adapter with the monitor or display, the sound adapter with loudspeakers, the printer. Many other devices are bidirectional in nature (hard disks, memory cards, all types of network or bus connectors) and can thus be counted among the output devices.
The number of devices you can link to a router will depend on the specific router,typically 4 devices can be connected.
127 USB devices are supported by one host controller.
This is similar to running too many programs on one computer. The computer's "brain" and RAM can't handle too many processes occurring at the same time, and wireless routers lock up when too many devices are connected because there is too much data transmission for them to handle at one time.