1. main objecttive
1.1. convenience
1.1.1. The OS as a User/Computer Interface
1.1.1.1. provides abstraction of hardware
1.1.1.2. making more convenient
1.1.2. Key Interface
1.1.2.1. ISA
1.1.2.1.1. defines repertoire of machine language
1.1.2.2. ABI
1.1.2.2.1. supports portability
1.1.2.3. API
1.1.2.3.1. can interface to OS through system calls
1.2. efficiency
1.2.1. The OS as Resource Manager
1.2.1.1. for moving, storing & process data
1.2.1.2. managing resources
1.2.1.3. control through software
1.2.1.3.1. as ordinary computer software
1.2.1.3.2. suite of programs, executed by processor
1.2.1.3.3. regain control to decide the next thing to process
1.3. ability to evolve
1.3.1. evolve over time for reasons
1.3.1.1. serial processing
1.3.1.1.1. earliest computers
1.3.1.1.2. problems
1.3.1.2. simple batch systems
1.3.1.2.1. computers are expensive
1.3.1.2.2. monitor (primitive o.s)
1.3.1.2.3. processor point of view
1.3.1.2.4. Job Control Language
1.3.1.2.5. Desirable Hardware Features
1.3.1.2.6. Modes Operation
1.3.1.2.7. overhead
1.3.1.3. multiprogrammed batch systems
1.3.1.3.1. processor is often idle
1.3.1.3.2. uniprogramming
1.3.1.3.3. multiprogramming
1.3.1.4. time sharing systems