Why we use return 0 and getch?

Answer 1

if you refering to c or c++ and its main function ... the return 0 defines the programm execution status ... 0 basucally means no errors and everything greater is a error. you do it if you catch an error and dont want the programm to crash (no clean up of resources, no freeing of shared memory , ect)

for the second question : getch
you have to provide more information or a context

Answer 2

it to return nothing in OOP