Single- and multi-tasking

A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program to be running in concurrency. This is achieved by time-sharing, dividing the available processor time between multiple processes that are each interrupted repeatedly in time slices by a task-scheduling subsystem of the operating system. Multi-tasking may be characterized in preemptive and co-operative types. In preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e.g., Solaris, Linux, as well as AmigaOS support preemptive multitasking. Cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking. 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking.

Single- and multi-user

Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem. A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, and the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources to multiple users.

Distributed

A distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they form a distributed system.

Templated

HUMAN COMPUTER INTERACTION

Human–computer interaction (HCI), alternatively man–machine interaction (MMI) or computer– human interaction (CHI) is the study of interaction between people (users) and computers.

"Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them."

1. A basic goal of HCI is

· to improve the interactions between users and computers

· by making computers more usable and receptive to the user's needs.

2. A long term goal of HCI is

· to design systems that minimize the barrier between the human's cognitive model of what they want

· to accomplish and the computer's understanding of the user's task.

· Why is HCI important?

· User-centered design is getting a crucial role!

It is getting more important today to increase competitiveness via HCI studies (Norman, 1990)

· High-cost e-transformation investments

· Users lose time with badly designed products and services

· Users even give up using bad interface