Simple Batch Systems- Resident Monitor program
- Users submit jobs to operator
- Operator batches jobs
- Monitor controls sequence of events to process batch
- When one job is finished, control returns to Monitor which reads next job
- Monitor handles scheduling
Job Control Language- Instructions to Monitor
- Usually denoted by $
- e.g.
- $JOB
- $FTN
- ... Some Fortran instructions
- $LOAD
- $RUN
- ... Some data
- $END
Desirable Hardware Features- Memory protection
- Timer
- To prevent a job monopolizing the system
- Privileged instructions
- Only executed by Monitor
- e.g. I/O
- Interrupts
- Allows for relinquishing and regaining control
Multi-programmed Batch Systems- I/O devices very slow
- When one program is waiting for I/O, another can use the CPU
Time Sharing Systems- Allow users to interact directly with the computer
- Multi-programming allows a number of users to interact with the computer
Operating System Support - Part 2
