GATE CS 1998 Q1.29 — I/O Scheduling

SPOOL (Simultaneous Peripheral Operations On-Line) is a technique where data is temporarily held in a buffer or disk space so that a slow peripheral device can process it at its own pace without holding up the CPU or active processes.

Let's analyze the options:

• Option A: An interactive terminal used for entering input data communicates directly with the running program in real-time and does not use spooling.
• Option B: A printer (or an output device printing jobs from multiple users) is the classic example of a spooled device. Since a printer is slow and can only handle one job at a time, multiple processes write their output to a spool file on the disk. The operating system then feeds these files to the printer sequentially, preventing the processes from being blocked.
• Option C: Secondary memory in a virtual storage system is managed via paging and segmentation, which is a memory management technique rather than I/O spooling.
• Option D: The swapping area on a disk is used by the OS scheduler to move entire processes in and out of main memory (swapping), which is distinct from spooling.

Thus, Option B is the correct answer.