SLR 04 – Operating systems – Systems software 13. OCR A Level (H046-H446) SLR4 – 1.2 Need for operating systems 14. OCR A Level (H046-H446) SLR4 – 1.2 Paging, segmentation and virtual memory 15. OCR A Level (H046-H446) SLR4 – 1.2 Interrupts 16. OCR A Level (H046-H446) SLR4 – 1.2 Scheduling 17. OCR A Level (H046-H446) SLR4 – 1.2 Types of operating system 18. OCR A Level (H046-H446) SLR4 – 1.2 BIOS 19. OCR A Level (H046-H446) SLR4 – 1.2 Device drivers 20. OCR A Level (H046-H446) SLR4 – 1.2 Virtual machines