OS History + Types

OS History + Types

1. History Phases

   • History Phase 1 - 1948/1970
     • Hardware expensive, humans cheap
     • One user at console at a time
     • Batch Monitor - Load program, run, print
     • Introduction of transistor
     • Direct Memory Access for I/O devices
     • Multiprogramming - Run multiple programs simultaneously
   • History Phase 2 - 1970/1985
     • Hardware cheaper, humans expensive
       • Multiple users can interact with the system at the same time
       • Problem: Thrashing
         • Performance falls adding users
   • History Phase 3 - 1981-
     • Hardware very cheap, humans very expensive
     • Personal computers
     • PCs become powerful
   • History Phase 4 - 1989-
     • Networking (LAN)
       • Connected machines
       • Client/server model
   • History Phase 5 - 1995-
     • Mobile systems
       • Laptops/phones etc.
     • Wireless/Wide Area Network
       • Internet

2. Types/Evolution

   • Batch Processing OS
     • Jobs submitted in sequential batches
     • No interactions with user
     • Monitor: Pieces of software controlling sequence in main memory
   • Time-sharing OS
     • Service to online users concurrently
     • Sharing CPU time and other resources
     • Protection between multiple jobs overwriting eachother
   • Real-time OS
     • Strict timing constraints on response
   • Network OS
     • Users can view other machines and read/copy/write files
     • Support diskless workstation environment
   • Distributed OS
     • Entire set of machines treated as single system