Question: what are the five classification of operating systems?
Answer: i) Multiuser OS: In a multiuser OS, more than one user can use the same system at a same time through the multi I/O terminal or through the network. ... 
ii) Multiprocessing OS: ... 
iii) Multiprogramming OS: ... 
iv) Multitasking OS: ... 
v) Multithreading: ... 
vi) Batch Processing: ... 
vii) Online Processing: