Connecting two computers to one monitor, keyboard amd mouse

How do I connect two desktop midi Tower computers to one monitor, keyboard and mouse?  At start-up would I have an option to choose either of the two computers?  Is this arrangement possible?  All responses would be appreciated.

what you need is a kvm switch.

http://en.wikipedia.org/wiki/KVM_switch

here's an example of one:- http://www.amazon.co.uk/Aten-CS22U-2-Port-Cable-Switch/dp/B002NTIZCG/ref=lp_430437031_1_10?s=computers&ie=UTF8&qid=1417208984&sr=1-10

you connect the keyboard, mouse and monitor to one side and on the other side connect the 2usb and vga cable (2 sets of 3 cables) to each pc.

now you just start 1 or both pc's and then choose which pc is displayed and controlled by simple clicking/switching the control switch.

more examples of kvm switches here :- http://www.newegg.com/KVM-Switches/SubCategory/ID-143

and here :- http://www.amazon.co.uk/s/ref=nb_sb_ss_i_0_3?url=search-alias%3Dcomputers&field-keywords=kvm%20switch&sprefix=kvm%2Ccomputers%2C220