What is the operating system used in fourth generation computers?
You can use any operation system in fourth generation computers.
Most first generation computers had no operating system. When they did, it was usually just something called a Batch Monitor, all it did was sequence through several jobs one at a time that had been submitted in a batch. The computer companies saw no need for any form of operating system, so the machine's users had to write them all themselves. It was not until the second generation computer that computer companies supplied operating systems…
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 (PS/2)" line of second-generation personal computers.