Direct changeover is one of the methods to change from an existing system to a new one.
This is the simplest methods of changeov. Imagine a new checkout system for a supermarket. If the implementation is done by direct changeover, then the supermarket will be closed for one night, all the old checkouts will be taken out, the new ones will be installed and the sup This is how the UK stock market was computerized in the 1980s. The old market closed on Friday night and the computers were all switched on the following Monday morning. Unfortunately, there was an error in the software, which made all the computers sell shares and carry on selling them. By the time human beings had intervened to stop the computers, half of the value of companies had been wiped off the stock market and many people had been ruined.