ENVS 1500 Lecture Notes - Lecture 22: Application Programming Interface, Word Processor, Multiprocessing
13 May 2018
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ENVS 1500 Lecture 22 Notes – OS Users
Introduction
• Most important, this includes the loading and execution of programs.
• When a user program is not being executed, the OS is always available to the user for
these purposes.
• The OS user interface provides a means for the user to get work done more quickly and
efficiently.
• This is especially true for the user interface found on modern operating systems.
• The best modern operating systems combine graphical simplicity with sophisticated text
command input capability and output display of results to provide the user with
powerful access to the facilities of the computer.
• Under most conditions, the computer system operates well below full capacity.
• The CPU sits idle while waiting for I/O transfers to occur.
• A user sits thinking at the keyboard.
• Multiuser and multitasking operating systems make it possible for many users or tasks
to share the computer resource, providing fuller utilization of the system.
• The operating system extends the capability of the computer to include features that
require special coordinated hardware and software that is invisible to the user.
• These features include virtual memory, cache memory, multiprocessing, vector
processors, and networking.
• The operating system provides powerful tools to the user’s programs that improve the
uality of the pogas ad ake the use’s wok easie.
• For example, modern OS tools allow work to be easily transferred between applications
through a clipboard
• Make it possible to embed a spreadsheet into a word processing document.
• System services are provided by an API, or Application Programming Interface.
• The API provides file and I/O services, tools that create and support the graphical user
interface, even tools to embed a spreadsheet into a word processing document.
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