Esquema de estudio para sistemas tema 2

Esquema de estudio para sistemas tema 2

1. OS Historical evolution

   • 1940
     • ▪ Vacuum valves. They were programmed with mechanical switches and haved high and complex machine setup time.
   • 1950
     • ▪ Transistors, the concept of Operating System appears. Data entry through punched cards or magnetic tapes.
   • 1960
     • ▪ Integrated circuits. They found new techniques to improve performance
       • Multiprogramming: allows holding in memory two or more processes to be executed concurrently
       • Time-sharing: allows the CPU to be distributed equally among the programs of the different users that are running.
       • Real time: systems in which the response time is required to be immediate such as air traffic control, patient monitoring, etc.
       • Multiprocessor: allows working with machines that have more than one processor
   • 1970
     • ▪ Microprocessors and minicomputers. C and Pascal programming languages.
   • 1980
     • ▪ High level languages, such as C++ (object oriented).
   • 1990
     • ▪ OS performance increases thanks to hardware improvement.

2. OS Structure

   • Monolithic structure
     • All the functionalities of the system are implemented in a single program and its difficult modifying or correcting mistakes. (Not used nowadays.)
   • Layered structure
     • OS is divided into several layers or levels, each layer is capable of communicating directly with immediately higher or lower layers by using service interfaces.
   • Modules structure
     • There is a separate module to implement each functionality. Each module communicates through interfaces with a central module called "Kernel".

3. OS Classification

   • Internal structure
     • Monolithic, layered, modules...
   • Number of users
     • SUOS (Single user operating system)
       • Capable of serving only ONE user at a time.
     • MUOS (Multi user operating system)
       • Capable of serving MULTIPLE users at a time.
   • Number of tasks
     • Monotasking
       • Only one program at a time is executed.
     • Multitasking
       • Several programs executed at the same time.
   • Number of processors
     • Monoprocessor
       • They can only work with one processor
     • Multiprocessor
       • They allow to manage several processors.
   • Licensing type
     • Propiertary
     • Free