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Tuesday, 20 February 2018

Types of operating systems

Types of operating systems:


a- Real-time- a multitasking operating system that executes real-time applications through specialised scheduling algorithms to determine their performance, aiming at quick and predictable response to events. They incorporate traits of both time sharing and event-driven properties. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.

b- Multi-user - allows multiple users to access a computer system at the same time e.g.: time-sharing systems and Internet servers. Single-user operating systems can only have one user at a time although they can still be multitask systems,meaning multiple programs running concurrently.

c- Multi-tasking vs. single-tasking
The former allows more than one program to be running at the same time, while the latter has only one running program. There are 2 types of multi-tasking system: pre-emptive (the operating system slices the CPU time and dedicates one slot to each of the programs) and cooperative (each process gives time to the other processes). 

d- Distributed - a group of independent computers behave like one single entity, similar to a network cluster. The processing is distributed across the participating machines.


e- Embedded - for use in embedded computer systems (small machines like PDAs). As they run on limited resources, their design is usually efficient considering the reduced autonomy with which they operate.

Friday, 16 February 2018

Ethnography

Ethnography is the study of people and cultures, analysing the latter from the former's viewpoint, documenting the cultural development of a group.

Originally an area of anthropologist interests, it has also become popular in the social sciences, communication studies and history. Ethnography is relevant for the understanding of ethnic differences, compositions and materialism/spirituality among the observed populations. A holistic study, it usually includes history and terrain and climate features. Its purpose is to provide a basic understanding of the varied styles in human social life.

The field of anthropology originated from Europe in late 19th century, arriving in the United States at the beginning of the 20th century. The founders of ethnography are considered to be EB Tylor (1832-1917) from Britain and Lewis H Morgan (1818-1881), from the us. Franz Boas (1858-1942), Bronislaw Malinowski (1858—1942), Ruth Benedict and Margaret Mead (1901-1978), were researchers who contributed the idea of cultural relativism to the literature, focusing on the use of documents and informants, including experiencing life as one of them.

Friday, 29 December 2017

Function Point

A function point measures how business-worthy an information system component is to the end user. As a single unit, the cost of a function point is based on previous projects. Although there is no widely recognised method in the sizing result, there have been many approaches to bring it closer to a standardising convention

As of 2013, these are −

ISO Standards
COSMIC − ISO/IEC 19761:2011 Software engineering. A functional size measurement method.

FiSMA − ISO/IEC 29881:2008 Information technology - Software and systems engineering - FiSMA 1.1 functional size measurement method.

IFPUG − ISO/IEC 20926:2009 Software and systems engineering - Software measurement - IFPUG functional size measurement method.

Mark-II − ISO/IEC 20968:2002 Software engineering - Ml II Function Point Analysis - Counting Practices Manual.

NESMA − ISO/IEC 24570:2005 Software engineering - NESMA function size measurement method version 2.1 - Definitions and counting guidelines for the application of Function Point Analysis.


Object Management Group (OMG), an open membership and not-for-profit computer industry standards consortium, has adopted the Automated Function Point (AFP) specification led by the Consortium for IT Software Quality.

Function Point Analysis (FPA) technique quantifies the functions within software that are meaningful to the users. The functions are based on the requirements specification.

Sunday, 12 November 2017

TCL commands

Transaction Control Language(TCL) commands manage transactions in database, usually the changes rbought about by DML statements (update, delete, insert).

Commit - used to permanently save any transaction into the database.

Rollback - undoes all changes, returning to the last committed stage. It can also be used in conjunction with the savepoint command when regression to an earlier state is desirable if savepoints were used rather than commit.

Savepoint - temporarily saves a transaction, thus allowing for a rollback operation to reverse back to this saved state. Savepoint is the only TCL command that needs to be named in order to be identified by a rollback operation.

The Weasel War Dance

In colloquial language, the weasel war dance is a set of moves done by a ferret to indicate playful behaviour. It consists of a frenzied series of hops sideways and backwards, often accompanied by an arched back, and a frizzed-out tail. Ferrets exhibit a pointed lack of spatial awareness when in this state,  often bumping into or falling over objects and furniture.  The dance includes a clucking vocalization, known as "dooking". 

Tuesday, 7 November 2017

Database Tuning

Database tuning is the process of fine tuning either the parameters of a database installation or the influencing properties of a db application in order to improve performance. It's often recommended with huge database systems due to the  complexity and amount of data to be handled.

Tuning is best done by highly specialised professionals even though it's a costly process with hardly noticeable results. A more cost-effective solution with similar effects can be achieved by hardware implementation. This restricts the need for tuning to a few areas, e.g.: high-end applications. Another option includes the optimisation of the data model by normalising its tables e.g.: using atomic fields and eliminating transitive dependencies.

Monday, 2 October 2017

critical path method (CPM)

The critical path method (CPM) is a progressive project management technique to separate critical and non-critical tasks in order to avoid bottlenecks and missed deadlines due to lack of priorisation. It's best suited for projects with a diverse range of activities in a way that enables their solving in an ordered manner. ideally, a flowchart is used for displaying how the tasks relate to each other (e.g.: how the output of an activity is the input of a subsequent process). It's also tops to determine beforehand the expected completion time for each task.

An activities model designed for project management, common elements of this model include time for the completion of each activity, the dependencies therein, milestones and deliverables. It makes use of the presentation capabilities of an operation flowchart, the outcomes pictured as knots while the accompanying relationships are represented by arrows. For this model to make sense, all individual project operations should be plotted with their respective durations.
Using the dynamics of the operation-duration relationships, CPM calculates the longest path of planned activities to logical end points or to the end of the project, and the earliest and latest that each activity can start and finish without delaying the whole project, as a means of providing a safe margin for work within a given deadline. This procedure distinguishes activities between "critical" and which have "total float", meaning, allowed some delay without compromising the project overall. This network of activities and their matching duration defines the shortest possible time to carry a project through to completion, with total float being unused time within the critical path.