If we use different relocation address for each process, how many process can we run on a system with say 4GB of RAM? Basically we are dividing main memory here for different processes and so, assuming equal division, suppose each process takes 100 MB of memory we can have maximum 40 processes only including all system ones. This also means that there is no way for any process to use more than 100 MB of memory in any case. I do not think any such system exist except may be in embedded domain. For this question, 'b' is also an answer- you can refer use of virtual memory in any good book. Also, these questions of GATE 1999 were having multiple correct answers and only if all were marked, they gave marks.