EXERCISE N° 1: LINUX

Warm Up To Penguins The Zen Of Xen One of the hottest recent topics in the computer industry at this time is virtualization. Products such as VMware and Microsoft’s Virtual PC are trying to take advantage of the increasing demand to run virtual computers on top of a physical host. There are several reasons to do this. If, for example, you need to run a number of different versions of Linux from time to time, you can run them as virtual systems on top of a stable host without worrying about constantly reinstalling or corrupting your system. For businesses, virtual machines let many users share a single physical host. Because a system rarely runs at 100% load all the time, you can usually load-balance and get more bang for your hardware buck with virtual systems. Linux, of course, has a virtualization application, too: Xen. Xen is an open-source project organized by XenSource which is in turn owned by Citrix, known for GotoMyPC among others. Xen consists of a hypervisor, which is simply a software package that enables virtual hosts to run on Linux, and the virtual hosts themselves. If you’ve ever used VMware, there are some significant differences between how VMware (and Virtual PC) handles virtualization and how Xen does it. For example, VMware runs as a program (or service) that the virtual hosts run inside, but Xen actually is part of the Linux Kernel. The “host” machine is just another virtual machine (or domain, as Xen calls them) running on the hardware. Although this may seem a bit strange conceptually, it seems to pay off performance-wise.

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REVIEW 2- SIMPLE PAST: HISTORY OF COMPUTING

HISTORY OF COMPUTING

Computing hardware has been an important component of the process of calculation and data storage since it became useful for numerical values to be processed and shared.

Devices to aid computation changed from simple recording and counting devices to the abacus, the slide rule, analog computers, and more recent electronic computers. Even today, an experienced abacus user using a device hundreds of years old can sometimes complete basic calculations more quickly than an unskilled person using an electronic calculator — though for more complex calculations, computers out-perform even the most skilled human.

This article covers major developments in the history of computing hardware, and attempts to put them in context. For a detailed timeline of events, see the computing timeline article. The history of computing article is a related overview and treats methods intended for pen and paper, with or without the aid of tables.

As early as 1725 Basile Bouchon used a perforated paper loop in a loom to establish the pattern to be reproduced on cloth, and in 1726 his co-worker Jean-Baptiste Falcon improved on his design by using perforated paper cards attached to one another for efficiency in adapting and changing the program. The Bouchon-Falcon loom was semi-automatic and required manual feed of the program.

In 1801, Joseph-Marie Jacquard developed a loom in which the pattern being woven was controlled by punched cards. The series of cards could be changed without changing the mechanical design of the loom. This was a landmark point in programmability.

Herman Hollerith invented a tabulating machine using punched cards in the 1880s.
In 1833, Charles Babbage moved on from developing his difference engine to developing a more complete design, the analytical engine, which would draw directly on Jacquard's punched cards for its programming.

In 1890, the United States Census Bureau used punched cards and sorting machines designed by Herman Hollerith, to handle the flood of data from the decennial census mandated by the Constitution. Hollerith's company eventually became the core of IBM. IBM developed punched card technology into a powerful tool for business data-processing and produced an extensive line of specialized unit record equipment. By 1950, the IBM card had become ubiquitous in industry and government. The warning printed on most cards intended for circulation as documents (checks, for example), "Do not fold, spindle or mutilate," became a motto for the post-World War II era.