CLKCSS - Scheduling Algorithm

This document details an assembly language implementation of a scheduling algorithm, specifically a routine named NXTJOB, authored by T. Hastings on June 29, 1965. The algorithm's core function is to optimize system performance by keeping I/O devices continuously busy and identifying the highest priority user for execution.

The NXTJOB routine begins by tracking I/O completion and manipulating I/O availability to simulate faster operations. It then systematically checks through various I/O device categories to find available resources. For each device category, it searches for waiting jobs, evaluating their runnability, checking their wait status bits, and assessing if they have exceeded their allocated quantum time. The code includes logic to manage job states, such as setting run times, clearing wait bits, and controlling scanner channels.

Key data structures defined include AVALTB (for I/O device availability flags), WAITB (for job waiting status bits), and QUANTS (defining quantum times for different job queues, such as magnetic tape, data control, dectape, I/O wait satisfied, and straight computation queues). The document also provides a comprehensive symbol table listing all variables, their addresses, and types used within the algorithm. The assembly concludes with a message confirming no errors were found.