One Last Point
As you review all of these answers, the answers will be a case of "depends". It not only depends on what you want to do with them (communicate? create documents? spreadsheets? Program the computers?) but also what your backround is. If you ask all of the questions, the answer will depend on whether you are talking to a mainframe person, a developer, someone who learned CP/M or DOS, or someone who worked with the MAC or even windows. Is the person tech-savy? or just a user who wants to run a web browser? Even amoung developers, there are those of us who like to work with machine-code and assembler and those who work with older laguages such as COBOL and FORTRAN and those who work with JAVA or with scripts.
The word "difficult" is always a relative term. It depends on one's idea of of "difficult". If you told a person who got a "blue screen" to debug the problem and come up with a solution, most of you probably would not be able to. I think it all depends.