CushionTheBlow (구 BluemoonSoft)

In software engineering, busy waiting or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as waiting for keyboard input or waiting for a lock to become available. It can also be used to delay execution for some amount of time; this was necessary on old computers that had no method of waiting a specific length of time other than by repeating a useless loop a specific number of times, but on modern computers with clocks and different processor speeds, this form of time delay is often inaccurate and a sign of a naive attempt at programming. Spinning can be a valid strategy in certain special circumstances, most notably in the implementation of spinlocks within operating systems designed to run on SMP systems. In general, however, it is considered an anti-pattern and should be avoided, as the CPU time spent waiting could have been reassigned to another task.

Reference:
http://en.wikipedia.org/wiki/Busy-loop

BogoMips (from "bogus" and MIPS) is an unscientific measurement of CPU speed made by the Linux kernel when it boots, to calibrate an internal busy-loop. An oft-quoted definition of the term is "the number of million times per second a processor can do absolutely nothing."

BogoMips can be used to see whether it is in the proper range for the particular processor, its clock frequency, and the potentially present CPU cache. It is not usable for performance comparison between different CPUs.

Reference:
http://en.wikipedia.org/wiki/Bogomips

The term jiffy (or jiffie) is used in different applications for various different short periods of time.

In general parlance, the term means any unspecified short period of time, or a moment, and is often used in the sense of the time taken to complete a task, as in, "I'll be done in a jiffy." Records of the term date to 1785. Its ultimate origin is unknown, but it is believed to have been thieves' cant for lightning.

Use in computing
In computing, a jiffy is the duration of one tick of the system timer interrupt. It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform.

Typically, this time is 0.01 seconds. Early microcomputer systems such as the Commodore 64 and many game consoles (which use televisions as a display device) commonly synchronize the system clock with the vertical frequency of the local television standard, either 59.94 Hz with NTSC systems, or 50.0 Hz with most PAL systems. Within the Linux 2.6 operating system kernel, since release 2.6.13, on the Intel i386 platform a jiffy is by default 4 ms, or 1/250th of a second. The jiffy value for other Linux versions and platforms have typically varied between about 1 ms and 10 ms.

Reference:
http://en.wikipedia.org/wiki/Jiffy_%28time%29

Rational ClearCase is a software tool for revision control (e.g. configuration management, SCM) of source code and other software development assets. It is developed by the Rational Software division of IBM. ClearCase forms the base of version control for many large and medium sized businesses and can handle projects with hundreds or thousands of developers, but the price is quite steep for smaller companies.

Rational supports two types of SCM configurations, UCM, and base ClearCase. UCM provides an out-of-the-box SCM configuration while base ClearCase supplies all the basic tools to make it very configurable and flexible. Both can be configured to support a wide variety of SCM needs.

ClearCase can run on a number of platforms including Linux, HP-UX, Solaris and Windows. It can handle large binary files, large numbers of files, and large repository sizes. It handles branching, labeling, and versioning of directories.

Reference:
http://en.wikipedia.org/wiki/Rational_ClearCase

BitKeeper is a software tool for revision control (configuration management, SCM, etc.) of computer source code. A sophisticated distributed system, BitKeeper competes largely against other professional systems such as Rational ClearCase and Perforce. BitKeeper is produced by BitMover Inc., a privately held company based in Campbell, California and owned by CEO Larry McVoy, who had previously designed TeamWare.

BitKeeper builds upon many of the TeamWare concepts. Its key selling point is the ease with which distributed development teams can keep their own local source repositories and still work with the central repository.

BitKeeper is proprietary software and is normally sold or leased (as part of a support package) to medium or large corporations.

History
BitMover used to provide access to the system for certain open source or free software projects, the most famous (and controversial) of which was the source code of the Linux kernel. The license for the "community" version of BitKeeper had allowed for developers to use the tool at no cost for open source or free software projects, provided those developers did not participate in the development of a competing tool (such as CVS, GNU Arch, Subversion or ClearCase) for the duration of their usage of BitKeeper plus one year. This restriction applied regardless of whether the competing tool is open/free or proprietary. This version of BitKeeper also required that certain meta-information about changes be stored on computer servers operated by BitMover (www.openlogging.org), an addition that makes it impossible for community version users to run projects of which BitMover is unaware.

Reference:
http://en.wikipedia.org/wiki/Bitkeeper

Unless you have a reason for doing otherwise, we recommend that you create the following partitions:

- A swap partition (at least 32MB) ? swap partitions are used to support virtual memory. In other words, data is written to a swap partition when there is not enough RAM to store the data your system is processing. The size of your swap partition should be equal to twice your computer's RAM, or 32MB, whichever amount is larger.

For example, if you have 1GB of RAM or less, your swap partition should be at least equal to the amount of RAM on your system, up to two times the RAM. For more than 1GB of RAM, 2GB of swap is recommended. Creating a large swap space partition will be especially helpful if you plan to upgrade your RAM at a later time.

- A /boot partition (100MB) ? the partition mounted on /boot contains the operating system kernel (which allows your system to boot Red Hat Linux), along with files used during the bootstrap process. Due to the limitations of most PC BIOSes, creating a small partition to hold these files is a good idea. For most users, a 100MB boot partition is sufficient.

* Warning
Do not create your /boot partition as an LVM partition type. The boot loaders included with Red Hat Linux cannot read LVM partitions and you will not be able to boot your Red Hat Linux system.

* Caution
While partitioning your hard drive, keep in mind that the BIOS in some older systems cannot access more than the first 1024 cylinders on a hard drive. If this is the case, leave enough room for the /boot Linux partition on the first 1024 cylinders of your hard drive to boot Linux. The other Linux partitions can be after cylinder 1024.

If your hard drive is more than 1024 cylinders, you may need to create a /boot partition if you want the / (root) partition to use all of the remaining space on your hard drive.

In the disk partitioning tool parted, 1024 cylinders equals 528MB (this exact number is dependent on your BIOS, however). Refer to http://www.pcguide.com/ref/hdd/bios/sizeMB504-c.html for more information.

- A root partition (1.7-5.0GB) ? this is where "/" (the root directory) will be located. In this setup, all files (except those stored in /boot) are on the root partition. A 1.7GB root partition will permit the equivalent of a personal desktop installation (with very little free space), while a 5.0GB root partition will let you install every package.

Reference:
http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/install-guide/s1-diskpartitioning.html

A device driver, or software driver, is a computer program allowing higher-level computer programs to interact with a device.

A driver typically communicates with the device through the computer bus or communications subsystem to which the hardware is connected. When a calling program invokes a routine in the driver, the driver issues commands to the device. Once the device sends data back to the driver, the driver may invoke routines in the original calling program. Drivers are hardware-dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface.

Reference:
http://en.wikipedia.org/wiki/Device_driver

In computer storage, logical volume management or LVM is a method of allocating space on mass storage devices that is more flexible than conventional partitioning schemes. In particular, a volume manager can concatenate, stripe together or otherwise combine partitions into larger virtual ones that can be resized or moved, possibly while it is being used.

Volume management is one of many forms of storage virtualization, the one implemented as a layer in the OS disk driver stack.

Reference:
http://en.wikipedia.org/wiki/Logical_volume

LVM is a logical volume manager for the Linux kernel. It was originally written in 1998 by Heinz Mauelshagen, who based its design on that of the LVM in HP-UX.

The installers for the Fedora, MontaVista Linux, openSUSE, SLES, SLED, Debian GNU/Linux, and Ubuntu distributions are LVM-aware and can install a bootable system with a root filesystem on a logical volume.

Reference:
http://en.wikipedia.org/wiki/Lvm

In computer science, a type system defines how a programming language classifies values and expressions into types, how it can manipulate those types and how they interact. A type identifies a value or set of values as having a particular meaning or purpose (although some types, such as abstract types and function types, might not be represented as values in the running computer program). Type systems vary significantly between languages with, perhaps, the most important variations being their compile-time syntactic and run-time operational implementations.

A compiler may use the static type of a value to optimize the storage it needs and the choice of algorithms for operations on the value. For example, in many C compilers the "float" data type is represented in 32 bits, in accordance with the IEEE specification for single-precision floating point numbers. Thus, C uses floating-point-specific operations on those values (floating-point addition, multiplication, etc.).

The depth of type constraints and the manner of their evaluation affect the typing of the language. Further, a programming language may associate an operation with varying concrete algorithms on each type in the case of type polymorphism. Type theory is the study of type systems, although the concrete type systems of programming languages originate from practical issues of computer architecture, compiler implementation, and language design.

Reference:
http://en.wikipedia.org/wiki/Statically_typed