Internet: www.economist.com (adapted).

Based on the text above, judge the following item.

1               The difficulty for health policy makers the world overis
         this: it is simply not possible to promote healthier lifestyles
         through presidential decree or through being overprotective
4       towards people and the way they choose to live. Recent history
         has proved that one-size-fits-all solutions are no good when
         public health challenges vary from one area of the country to
7       the next. But we cannot sit back while, in spite of all this, so
        many people are suffering such severe lifestyle-driven ill health
       and such acute health inequalities.
   
        Internet: <www.gov.uk> (adapted).

          The aging process affects us all at different rates. Some people of fifty-three, like the esteemed author, look a mere thirty-five, with sparkling brown eyes, a handsome gait and the virility of a steam train. Others, like the author’s friend Colin, look like little middle-aged men at twenty-one with middle-aged outlooks of set ways and planned futures. In women the former condition is common but women rarely suffer from the latter, being fired with the insatiable drive of ambition for either an independent and distinguished career in a still male-dominated world, or a home and seven children by the time they are thirty followed by an independent and distinguished career as a Cheltenham councillor or a public relations agent for Jonathan Cape, in later life.
         No such luck for Charles Charlesworth, who was born on the 14th of March, 1829, in Stafford. At the age of four Charles had a beard and was sexually active.
         In the final three years of his life his skin wrinkled, he developed varicose veins, shortness of breath, grey hair, senile dementia and incontinence. Some time in his seventh year he fainted and never gained consciousness
         The coroner returned a verdict of natural causes due to old age.

Hugh Cory. Advanced writing with english in use. Oxford University Press, p. 34.

Repeaters and hubs

A repeater is an electronic device that receives a network signal, cleans it of unnecessary noise, and regenerates it. The signal is retransmitted at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. A repeater with multiple ports is known as a hub. Repeaters work on the physical layer of the OSI model. Repeaters require a small amount of time to regenerate the signal. This can cause a propagation delay which can affect network performance. As a result, many network architectures limit the number of repeaters that can be used in a row, e.g., the Ethernet 5-4-3 rule.
Hubs have been mostly obsoleted by modern switches; but repeaters are used for long distance links, notably undersea cabling.


Bridges

A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model to form a single network. Bridges broadcast to all ports except the port on which the broadcast was received. However, bridges do not promiscuously copy traffic to all ports, as hubs do. Instead, bridges learn which MAC addresses are reachable through specific ports. Once the bridge associates a port with an address, it will send traffic for that address to that port only.
Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, the bridge assumes that the MAC address is associated with that port and stores its source address.
The first time a bridge sees a previously unknown destination address, the bridge will forward the frame to all ports other than the one on which the frame arrived.

Bridges come in three basic types:

Local bridges: Directly connect LANs

Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers. Wireless bridges: Can be used to join LANs or connect remote devices to LANs.

Internet: http://en.wikipedia.org (adapted).

Types of operating systems

Real-time
A real-time operating system is a multitasking operating system that aims at executing real-time applications. Real-time operating systems often use specialized scheduling algorithms so that they can achieve a deterministic nature of behavior. The main objective of real-time operating systems is their quick and predictable response to events. They have an event-driven or time-sharing design and often aspects of both. 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.

Multi-user
A multi-user operating system allows multiple users to access a computer system at the same time. Time-sharing systems and Internet servers can be classified as multi-user systems as they enable multiple-user access to a computer through the sharing of time. Single-user operating systems have only one user but may allow multiple programs to run at the same time.

Multi-tasking vs. single-tasking
A multi-tasking operating system allows more than one program to be running at the same time, from the point of view of human time scales. A single-tasking system has only one running program. Multi-tasking can be of two types: pre-emptive and co-operative. In pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and Linux support pre-emptive multitasking, as does AmigaOS. Cooperative multitasking is achieved by relying on each process to give 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 pre-emptive multi-tasking. Mac OS prior to OS X used to support cooperative multitasking.

Distributed
A distributed operating system manages a group of independent 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 make a distributed system.


Embedded
Embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE and Minix 3 are some examples of embedded operating systems.

Internet: http://en.wikipedia.org (adapted)