I am making a control system project for factories where the motors and other appliances are supposed to be controlled via touchscreen. Is there a separate software in which the screen buttons has to be designed for taking input and showing whether on or off?
Depends on what touch screen you are using.
For a resistive touch screen, like the ones on Nintendo DS, you will need Anlog to Digital converters. These can all be obtained at Spark Fun. The A2Ds will read the analog (changing) voltage of the x axis movement and y axis movement and out put them digitally to the GPIO pins on the Raspberry. You will read this data via SPI and do what ever it is that you want with the data. It is quite a project, will take some time and experimenting but it is not difficult. There may be code online if you google that may get you started with the raspberry.
Sample touch screen projects:
DS Touch Screen Also you will need an LCD for the touch screen to sit on top of. There are other LCD screens that come with touch capabilities but you will have to pay attention to how it interfaces (I2C, I2S, SPI etc.)
Raspberry Pi 2 supported interfaces at the top I've made a project of this before a while back and it was neat but definitely a project.
There's another type of touch screen which is capacitive. Which I have not used but I imagine it would require A2Ds as well.