If you have multiple computers and not enough monitors or enough monitors but not enough space to set everything up, then there is good news. It's possible to share a monitor. There are various ways.
1. KVM Switch
A KVM Switch or Keyboard Video Mouse switch, allows you to hook up more than one computer to a monitor. My examples are all VGA based. You take a VGA cable and hook one end to the end port of the KVM and the other to your monitor. Then you hook up your computers to the side ports of the Switch. Other designs may have a slightly different setup. Then it's just a matter of cycling through the computers by pressing the button on the device. I can also hook up a keyboard and mouse. So I could hook up one monitor, one keyboard and one mouse to 2 or 4 computers or more. The small ones in my picture are for 2 computers and the larger ones can handle 4 each.
From experience, switching monitors, no real issues but mouse and keyboard switching, it's so-so.
2. HDMI Switch
I have an HDMI Switch hooked up here. This one does not support keyboard and mouse. Here I have the output wire at the bottom connected to my TV. The two wires at the top are connections from my cable box and my Windows 7 Acer Desktop. Using the select button I can cycle through up to three devices with this model.
I also like to point out this one comes with a handy-dandy little remote-control to make switching from one source to the next a lot easier than fumbling with the select switch on the device.
A third option is to use your TV as a monitor. I do it on and off all the time. Most modern day TVs come with an assortment of plugins on the back. I have an older Acer desktop that I use for backup that I have connected to my TV. I have to click on the source button to switch the input device. In my case, my button is labeled TV Input. It might also say, Input, Source, Video Input, etc, depending on the brand of TV and remote.
Your monitor, like TVs, may have more than one input. If so, you can hook up a different computer to each input and then go into the monitor menu and switch the Input. My HP LP1965 monitor has a button labeled Input.
To sum up, too many computers, lack of space, just share your monitor.