Evolution of OS, Early Operating Systems, Generation Of Operating System
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Evolution of OS:
• The evolution of operating systems went through seven
major phases.
• Six of them significantly changed the ways in which users
accessed computers through the open shop, batch
processing, multiprogramming, timesharing, personal
computing, and distributed systems.
• In the seventh phase the foundations of concurrent
programming were developed and demonstrated in model
operating systems.
Early Operating Systems
• Early computers
– Single-user batch processing
• Only one job or task at a time
• Process data in groups (batches)
• Decks of punched cards
• Operating systems
– Software systems
– Manage transitions between jobs
– Increased throughput
• Amount of work computers process
Early Operating Systems
• Multiprogramming
– Many jobs or tasks sharing computer’s resources
– “Simultaneous” operation of many jobs
• Timesharing
– 1960s
– Special case of multiprogramming
– Users access computer through terminals
• Devices with keyboards and screens
• Dozens, even hundreds of users
– Perform small portion of one user’s job, then moves on
to service next user
– Advantage:
• User receives almost immediate responses to requests