Evolution of OS

Evolution of OS:

Evolution of OS is divided in 5 phases:
Phase 0: (1940-1955): 

• Computers are exotic experimental equipment. 
• Program in machine language. 
• Use plug boards to direct computer. 
• No overlap between computation, I/O, think time, and response time. 
• Programs manually loaded via card decks.

Phase 1 (1955-1970):

• User at console: one user at a time 
• OS becomes a batch monitor. 
• OS were written in Assembly languae.
• No structured programming.
• More efficient use of hardware. 
• No protection 
• difficult to debug!

Phase 2 (1970-1980): 

• Interactive timesharing. 
• One of the first timesharing systems. 
• To let multiple users interact with the system at the same time.
• Users do debugging, editing, and email online.
• More than one user executes their tasks simultaneously.

Phase 3 (1980-1990):

• Created MS- DOS. 
• GUI operating systems was developed first time. 
• Microsoft Windows: Win 1.0 (1985) .
• Phase 4 (1990-2000):  
• Networked Systems: (LAN). 
• Different machines share resources, printers, File Servers, Web Servers.
• Internet service providers (service between OS and apps). 

Phase 5 (2000-present): 

• Mobile and computer operating systems have been developed in different ways and for different uses. 
• Computer OS products are older and more familiar to larger groups of users. 
• Through this time, Microsoft Windows and Apple's Mac OS have emerged as the two dominant operating system designs.
• So many types of GUI operating systems are develop in phase 5 major types are: OS system of mobiles. window 95, window 98, window XP, window crystal vista window 8, window 10.

Operating Systems:

EasyExamNotes.com covered following topics in Operating Systems.

• Introduction to Operating Systems
• Function of OS
• Evolution of OS 
• Different Types of OS
• Desirable Characteristics and features of an OS
• Operating Systems Services
• Utility Programs
• System Calls
• File Systems: File Concept
• Contiguous disk space allocation met
• Directory Structures
• Disk Scheduling Algorithms
• FCFS Disk Scheduling Algorithms
• SSTF Disk Scheduling Algorithms
• SCAN Disk Scheduling Algorithms
• CSCAN Disk Scheduling Algorithms
• LOOK Disk Scheduling Algorithms
• CLOOK Disk Scheduling Algorithms.
• CPU Scheduling
• CPU Scheduling Concepts
• CPU Scheduling Algorithms
• FCFS CPU scheduling algorithm
• Nonpreemptive SJF CPU scheduling algorithm
• Preemptive SJF (SRTF) CPU scheduling algorithm
• Round Robin CPU scheduling algorithm
• Process Concept
• Process State Diagram
• Types of Schedulers
• System calls for Process Management
• Multiple Processor Scheduling
• Concept of Threads
• Memory Management
• Different Memory Management Techniques
• Swapping
• Segmentation
• Paging
• Paging vs Swapping
• Paging vs Segmentation
• Overlay in memory management
• FCFS page replacement algorithm
• LRU page replacement algorithm 
• Optimal page replacement algorithm
• Critical Section Problem
• Deadlock Avoidance, Recovery

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