Admin, Overview & History Flashcards
What is an Operating System?
The low-level software that supports a computer’s basic functions, such as scheduling tasks and controlling peripherals. The one program running at all times on the computer
What is the purpose of Operating System?
Resource Mangement /
Provide an environment for execution of programs
Provide services to programs and users
Phase 1: Serial Processing
1940s – 50s
* No Operating System,
programmers interacted
directly with hardware
* Signed up for blocks of time
* Potential for wasted time
* I/O took a long time
* CPU idle
Phase 2: Simple Batch Systems
- 1950s – 60s
- Programmers no longer have
direct to the hardware - Submit jobs to computer
operator who bundles a group of
jobs into a batch - Resident program – monitor –
accepts a batch, and processes
jobs sequentially, with minimal
pauses between
Phase 3: Multi-programmed Batch Systems
- 1960s – 70s
- Automatic job sequencing
removes the gaps between jobs,
but still the processor is often idle - I/O devices are slow, time spent
waiting for them - Multiprocessing allows operating
system to switch to a different job
when active job is waiting for I/O - UNICS (later UNIX): became a
foundation for modern operating
systems.
Phase 4: Time-Sharing
Multi-programmed batch systems can be quite efficient
* But do not allow user interaction
* Time-sharing systems take it one step further and allow
user interaction
* Trade-off between maximising user processing and minimising
response time
Key Features of Operating Systems
- User Interface
- Process Management
- Memory management
- Information Protection & Security
- Scheduling & Resource Management
- Communication
- Error Detection
System Calls interface
- Programming interface to the services provided by the OS
- Mostly accessed by programs via a high-level Application
Program Interface (API) rather than direct system calls - Act as a bridge between user-mode and kernel-mode operations
What is a System Program?
An OS System Program—software to provide useful
functions, utilities, and services.
* System Programs are not part of the kernel but operate in
user space
* Leverage System Calls to interact with the kernel and
manage resources.
* Some are simply user interfaces to system calls; others are
considerably more complex
3 most common system call types
- Three most common:
- Win32 API for Windows
- POSIX API: for all POSIX-based systems (*nix, OS X, Android)
- Java API for the Java Virtual Machine (JVM)
Name the System Programs?
- File management
- Status information and debugging
- File modification
- Programming-language support
- Program loading and execution
- Communications
- Background Services
