Recycling old Laptop Parts to make Digital Typewriter?
I have a Lenovo Laptop B590 and when it becomes obsolete and unusable I want to use the parts and build an extremely lightweight "digital typewriter" to be just able to type documents, use the mouse. and save to a memory source (either hard drive or flash). This is practically like a "Notepad". This will make it especially convenient to type while in cars, planes, etc., and be able to transport it easily. Please ELI5, I have no experience in building computers...
I don't need any USB ports, WiFi, any sort of powerful processor, disk reader, etc. I just want to build a laptop with the essential parts to do the actions above.
Do I need to make an OS, or is there like typing OS's out there?
Is this not possible, or am I going to have to just get like, Chrome OS or Ubuntu on my current laptop without making the laptop as lightweight as possible?