Betriebssysteme an der Humboldt-Universität zu Berlin

• Software between applications and hardware
• Responsible for providing execution environment to applications:
  • Providing abstractions
  • Protection (& Sharing)
  • Resource Management

• Provide abstractions
  • Raw hardware devices are difficult to use
  • Create virtual resources that are more usable
  • Make unreliable resources “reliable”
  • Make finite resources (e.g. memory, CPU) “infinite”
• Protection (& Sharing)
  •  Run multiple applications safely
  • Mechanisms to prevent applications from crashing the system
  • Which user is allowed to use the system / to access a resource?
• Resource Management
  • Resources are always limited
  • Make resource usage fair
  • Accounting
    May 2006 - 3

- File system instead of disk blocks
- 4GB continuous virtual memory vs. 1GB fragmented physical memory
- Reliable network connection instead of noisy network link

What if a program starts randomly accessing memory?

What if a user tries to consume all system resources?

What if many programs are running infinite loops?

What if many programs are requesting lots of memory?

primitive operating system in charge of executing the
batch job

-resided permanently in memory

- monitored the execution of each job

- Control Card Interpreter
(read & carry out card instructions)
- Loader (load system programs
& applications into memory)
- Controls for peripheral devices

combine multiple user jobs into a single batch job

- each user job would be executed in turn

- users received output after all jobs finished

Simultaneous Peripheral Operation OnLine

- Overlap I/O of one job with computation of another job.
While executing one job, the OS:
- reads next job from card reader into a storage area on the disk
(job queue).
- outputs printout of previous job from disk to printer.

process of storing the state of a process or thread, so that it can be restored and resume execution at a later point. 

This allows multiple processes to share a single CPU

multiple jobs are kept in main
memory at the same time.

CPU is assigned sequentially, i.e. when a job finishes another can
start immediately, while the free memory partition is being reloaded.

- CPU:
- Arithmetic Logic Unit
- Control Unit

- Memory Unit
- I/O Devices
- Busses

- had to sign up to use for allotted time