Abacus Definition, What is Abacus

An abacus is a mechanical device used to aid an individual in performing mathematical calculations.

The Origin of the Abacus

The origins of the abacus are disputed, as many different cultures have been known to have used similar tools. It is known to have existed in Babylonia and in China, with invention to have taken place between 1000 BCE and 500 BCE. The first abacus was almost certainly based on a flat stone covered with sand or dust. Lines were drawn in the sand and pebbles used to aid calculations. From this, a variety of abaci were developed; the most popular were based on the bi-quinary system, using a combination of two bases (base-2 and base-5) to represent decimal numbers.

The use of the word abacus dates back to before 1387 when a Middle English work borrowed the word from Latin to describe a sandboard abacus. The Latin word came from abakos, the Greek genitive form of abax ("calculating-table"). Because abax also had the sense of "table sprinkled with sand or dust, used for drawing geometric figures," it is speculated by some linguists that the Greek word may be derived from a Semitic root, ābāq, the Hebrew word for "dust." Though details of the transmission are obscure, it may also be derived from the Phoenician word abak, meaning "sand". The plural of abacus is abaci.

Babylonian Abacus

A tablet found on the island of Salamis (near Greece) in 1846 dates back to the Babylonians of 300 BCE making it the oldest counting board discovered so far. It was originally thought to be a gaming board.

Its construction is a slab of white marble measuring 149 cm in length, 75 cm in width and 4.5 cm thick, on which are 5 groups of markings. In the center of the tablet are a set of 5 parallel lines equally divided by a vertical line, capped with a semi-circle at the intersection of the bottom-most horizontal line and the single vertical line. Below these lines is a wide space with a horizontal crack dividing it. Below this crack is another group of eleven parallel lines, again divided into two sections by a line perpendicular to them but with the semi-circle at the top of the intersection; the third, sixth and ninth of these lines are marked with a cross where they intersect with the vertical line.

Roman Abacus

The Late Empire Roman abacus shown here in reconstruction contains eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each.

The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives—five units, five tens, etc., essentially in a bi-quinary coded decimal system, obviously related to the Roman numerals. The short grooves on the right may have been used for marking Roman ounces.

Computations are made by means of beads which would probably have been slid up and down the grooves to indicate the value of each column.

Chinese Abacus

The suanpan (Simplified Chinese: 算盘, Traditional Chinese: 算盤; pinyin: suànpán) of the Chinese is similar to the Roman abacus in principle, though has a different construction, and it was designed to do both decimal and hexadecimal arithmetics.

The Chinese abacus is typically around 20 cm (8 inches) tall and it comes in various widths depending on the application. It usually has more than seven rods. There are two beads on each rod in the upper deck and five beads each in the bottom for both decimal and hexadecimal computation. The beads are usually rounded and made of a hard wood. The beads are counted by moving them up or down towards the beam. The abacus can be reset to the starting position instantly by a quick jerk along the horizontal axis to spin all the beads away from the horizontal beam at the center.

Chinese abaci can be used for functions other than counting. Unlike the simple counting board used in elementary schools, very efficient suanpan techniques have been developed to do multiplication, division, addition, subtraction, square root and cube root operations at high speed.

Bead arithmetic is the calculating technique used with various types of abaci, in particular the Chinese abacus. The similarity of the Roman abacus to the Chinese one suggests that one could have inspired the other, as there is some evidence of a trade relationship between the Roman Empire and China. However, no direct connection can be demonstrated, and the similarity of the abaci may be coincidental, both ultimately arising from counting with five fingers per hand. Where the Roman model (like most modern Japanese) has 4 plus 1 bead per decimal place, the standard Chinese abacus has 5 plus 2, allowing less challenging arithmetic algorithms, and also allowing use with a hexadecimal numeral system. Instead of running on wires as in the Chinese and Japanese models, the beads of Roman model runs in groves, presumably making arithmetic calculations much slower. Possibly the Roman abacus was used primarily for simple counting.

Japanese Abacus

Traditional Chinese weighing units used a hexadecimal system which necessitated two beads on the upper deck. The Japanese first eliminated one bead from the upper deck and later another bead from the lower deck in each column of the Chinese abacus, making the Japanese abacus purely for the decimal system. The Japanese also eliminated the use of the Qiuchu (Chinese division table). However, the Chinese division table was still used when there were 5 lower beads. There came the debate of the multiplication table versus the division table, with the school of multiplication table prevailing in the 1920s. The rods (number of digits) usually increase to 21, 23, 27 or even 31, thus allowing calculation for more digits or representations of several different numbers at the same time.

Soroban is taught in primary schools as a part of lessons in mathematics because the decimal numerical system can be demonstrated visually. When teaching the soroban, a song-like instruction is given by the teacher. The soroban is about 8 cm (3 inches) tall. The beads on a soroban are usually shaped as a double cone (bi-cone) to facilitate ease of movement. Often, primary school students may bring along with them two sorobans, one with 1 upper bead and 5 lower beads, the other with 1 upper bead with 4 lower beads. Despite the advent of handheld calculators, some parents send their children to private tutors to learn soroban because proficiency in soroban calculation can be easily converted to mental arithmetic at a highly advanced level.

Russian Abacus

The Russian abacus, the schoty (счёты), usually has a single slanted deck, with ten beads on each wire (except one wire which has four beads, for quarter-ruble fractions). This wire is usually near the user. (Older models have another 4-bead wire for quarter-kopeks, which were minted until 1916.) The Russian abacus is often used vertically, with wires from left to right in the manner of a book. The wires are usually bowed to bulge upward in the center, in order to keep the beads pinned to either of the two sides. It is cleared when all the beads are moved to the right. During manipulation, beads are moved to the left. For easy viewing, the middle 2 beads on each wire (the 5th and 6th bead) usually have a colour different to the other 8 beads. Likewise, the left bead of the thousands wire (and the million wire, if present) may have a different color.

The Russian abacus is still in use today in shops and markets throughout the former Soviet Union, although it is no longer taught in most schools.

School Abacus

Around the world, abaci have been used in pre-schools and elementary schools as an aid in teaching the numeral system and arithmetic. In Western countries, a bead frame similar to the Russian abacus but with straight wires has been common (see image). It is still often seen as a plastic or wooden toy.

The type of abacus shown here is often used to represent numbers without the use of place value. Each bead and each wire has the same value and used in this way it can represent numbers up to 100.

The most significant educational advantage of using an abacus, rather than loose beads or counters, when practicing counting and simple addition is that it gives the student an awareness of the groupings of 10 which are the foundation of our number system. Although adults take this base 10 structure for granted, it is actually difficult to learn. Many 6 year olds can count to 100 by rote with only a slight awareness of the patterns involved.

Native American Abacus

Some sources mention the use of an abacus called a Nepohualtzintzin in ancient Aztec culture. This Mesoamerican abacus uses the 5-digit base-20 system.

The khipu of the Incas was a system of knotted cords used to record numerical data - like advanced tally sticks—but was not used to perform calculations. Calculations were carried out using a yupana (quechua for "counting tool"; see figure) which was still in use after the conquest of Peru. The working principle of a yupana was unknown up to very recent years (2001) when an explanation of the mathematical basis of these instruments has been proposed: comparing the form of several yupanas, it appears that calculations were based using the Fibonacci sequence 1,1,2,3,5 and powers of 10, 20 and 40 as place values for the different fields in the instrument. The Fibonacci sequence is useful to keep the number of grains within any one field at minimum.

Drive Definition, What is a Drive

The A: Drive is a physical drive located on IBM or PC compatible computers. The A: drive is a drive letter that is almost always used for the 3.5-inch floppy disk drive today, but an older computer may be the 5.25-inch drive.

The A: drive is usually the first boot-able drive on IBM compatible computers that helps enable users to use boot-able floppy diskettes to fix and repair their computer.

B: Drive is also another commonly known disk drive just like the A: drive. I know this information is a bit archaic, but never-less, you should at least now about the old school parts of a PC.

System Account Definition, What is a System Account

A system account is a membership with a multi-user network, online service, computer or other device or service that keeps track of various personal information such as rights or privileges, user personal information, access information and various other information about the user or his / her account.

ACPI Definition, What is ACPI

The Advanced Configuration and Power Interface (ACPI) specification is an open industry standard first released in December 1996 developed by HP, Intel, Microsoft, Phoenix and Toshiba that defines common interfaces for hardware recognition, motherboard and device configuration and power management. According to its specification[1], "ACPI is the key element in Operating System-directed configuration and Power Management (OSPM)".

The most widely recognized element of the standard is power management, of which there have been two major improvements. First, it puts the operating system (OS) in control of power management. Conversely, the previously existing APM model assigns power management control to the BIOS, with limited intervention from the OS. In ACPI, the BIOS provides the OS with methods for directly controlling the dirty details of the hardware so it has nearly complete control over the power savings.

The other important feature of ACPI is in bringing power management features previously only available in portable computers to desktop computers and servers. Extremely low consumption states, i.e. in which only memory, or not even memory is powered, but from which ordinary interrupts (real time clock, keyboard, modem, etc.) can quickly wake the system. These modes were previously only available in portable computers.

The standard supports keys on a normal keyboard for suspending or powering off the computer. Some vendors (e.g. ASUS and Compaq) have extended this feature and use it for other keys, especially so-called Power management keys.

ACPI cannot be applied to older hardware; for it to work, the operating system, the motherboard chip-set  and for some functions even the CPU need to be designed for it.

ACPI uses its own ACPI Machine Language (or AML) for implementing power event handlers, rather than the native assembly language of the host system.

The first version of Microsoft Windows to support ACPI was Windows 98. Linux, FreeBSD, NetBSD and OpenBSD all have at least some support for ACPI, though problems tend to arise from buggy implementations, especially those which Microsoft platforms and the Microsoft compiler support (though the implementation is not standards-compliant). Some people misinterpret this as the Microsoft tools being able to work around the bugs, when in fact the Microsoft tools simply allow the bugs to go unchecked and handle them in a non-standards-conforming way.


ACPI Global States

The ACPI specification defines the following seven states (so-called global states) an ACPI-compliant computer system can be in:

G0 Working is the normal working state of the computer, meaning that the operating system and whatever applications run. The CPU(s) execute instructions. Within this state (i.e., without entering G1 Sleeping), it is possible for CPU(s) and devices like hard drives, DVD drives, etc. to be repeatedly put into and come back from low-energy states, called C0–Cn and D0–D3. (Laptops, for example, routinely power down all currently unused devices when running on battery; some computers do this to reduce noise.)

G1 Sleeping subdivides into the four states S1 through S4. The time needed to bring the system from here back into G0 Working (wake-latency time) is shortest for S1, short for S2 and S3, and not so short for S4.

• S1 is the most power-hungry of sleep modes. All processor caches are flushed, and the CPU(s) stop executing instructions. Power to the CPU(s) and RAM is maintained; devices that do not indicate they must remain on may be powered down. Some newer machines do not support S1; older machines are more likely to support S1 than S3.
• S2 is a deeper sleep state than S1, where the CPU is powered off; however, it is not commonly implemented.
• S3 is called Standby in Windows, Sleep in Mac OS X, and sometimes also Suspend to RAM (STR), although the ACPI specification mentions only the term Sleep. In this state, main memory (RAM) is still powered, although it is almost the only component that is. Since the state of the operating system and all applications, open documents, etc. lies all in main memory, the user can resume work exactly where he/she left off—the main memory content when the computer comes back from S3 is the same as when it was put into S3. (The specification mentions that S3 is rather similar to S2, only that some more components are powered down in S3.)
• (Main article: Hibernate (OS feature)). S4 is called Hibernation in Windows, Safe Sleep in Mac OS X, and sometimes also Suspend to disk, although the ACPI specification mentions none of these terms. In this state, all content of main memory is saved to a hard drive, preserving the state of the operating system, all applications, open documents etc. That means that after coming back from S4, the user can resume work where it was left off in much the same way as with S3. The difference between S4 and S3, apart from the added time of moving the main memory content to disk and back, is that a power loss of a computer in S3 makes it lose all data in main memory, including all unsaved documents, while a computer in S4 is unaffected. (S4 is quite different from the other S states and actually resembles G2 Soft Off and G3 Mechanical Off more than it resembles S1–S3.)

G2 Soft Off (also known as S5) is almost the same as G3 Mechanical Off, which means among other things that the boot procedure must be run to bring the system from G2 to G0 Working. A key difference is that G3 Mechanical Off is entered only when a power loss occurs, whereas G2 is initiated by the operating system (typically because the user issued a shutdown command in some way). Additionally, for functionality like starting the system when the space bar on the keyboard is pressed, some components remain powered in G2, which means the computer is not safe for dis-assembly in this state.

G3 Mechanical Off: The computer's power consumption is very close to zero, to the point that the power cord can be removed and the system is safe for dis-assembly (typically, only the real-time clock is running off its own small battery). The computer falls into this state when a power loss occurs, e.g. in case of a power outage. Once power is restored, a full boot procedure is necessary to bring the system from G3 to G0 Working.

Furthermore, a state Legacy is defined as the state when an operating system runs which does not support ACPI. In this state, the hardware and power is not managed via ACPI, effectively disabling ACPI.


ACPI Device States

The device states D0-D3 are device-dependent:

• D0 Fully-On is the operating state.
• D1 and D2 are intermediate power states whose definition varies by device.
• D3 Off has the device powered off and unresponsive to its bus.

ACPI Processor States

The CPU power states C0-C3 are defined as follows:

• C0 is the operating state.
• C1 (often known as Halt) is a state where the processor is not executing instructions, but can return to an executing state essentially instantaneously.
• C2 (often known as Stop-Clock) is a state where the processor maintains all software-visible state, but may take longer to wake up.
• C3 (often known as Sleep) is a state where the processor does not need to keep its cache coherent, but maintains other state. Some processors have variations on the C3 state (Deep Sleep, Deeper Sleep, etc.) that differ in how long it takes to wake the processor.

ACPI Performance States

While a device or processor is operating (D0 and C0, respectively), it can be in one of several power-performance states. These states are implementation-dependent, but P0 is always the highest-performance state, with P1 to Pn being successively lower-performance states, up to an implementation-specific limit of n no greater than 16.

P-states in Intel processors are called SpeedStep, and in AMD processors, Cool'n'Quiet.


ACPI Critique

ACPI is a complex specification (over 500 pages long) that contains multiple components, including declarative tables, an imperative byte-code, and specific hardware components. Concerns have been repeatedly raised that an implementation of ACPI has to run complex, untrusted and potentially buggy bytecode with full privileges, thus potentially making any system that implements ACPI unstable and/or insecure.

Where hardware is non-conforming to ACPI, but claims to be, the software interoperating with that hardware is faced with a dilemma: Either it can be written to be ACPI-compliant, thus risking problems with the not-entirely-compliant hardware, or it can deviate from the ACPI standard to accommodate the hardware quirks. That, however, is generally seen as undesirable from a software-engineering point of view, since the software would potentially have to be adapted for and tested with arbitrarily large numbers of hardware devices, which is precisely what standards such as ACPI are intended to avoid. This is a constant debate between "standards purists" (mainly in the Linux community) and advocates of software that "simply works" with as much hardware as possible.

Access Definition, What is Access

Microsoft Access (current full name Microsoft Office Access) is a relational database management system from Microsoft, packaged with Microsoft Office Professional which combines the relational Microsoft Jet Database Engine with a graphical user interface.

Microsoft Access can use data stored in Access/Jet, Microsoft SQL Server, Oracle, or any ODBC-compliant data container. Skilled software developers and data architects use it to develop powerful, complex application software. Relatively unskilled programmers and non-programmer "power users" can use it to build simple applications without having to deal with features they don't understand. It supports substantial object-oriented (OO) techniques but falls short of being a fully OO development tool.

Microsoft Access was also the name of a communications program from Microsoft, meant to compete with ProComm and other programs. This Microsoft Access proved a failure and was dropped. Years later Microsoft reused the name for its database software.


Microsoft Access History

Microsoft Access version 1.0 was released in November 1992.

Microsoft specified the minimum operating system for Version 1.1 as Microsoft Windows v3.0 with 4 MB of RAM. 6 MB RAM was recommended along with a minimum of 8 MB of available hard disk space (14 MB hard disk space recommended). The product was shipped on seven 1.44 MB diskettes. The manual shows a 1993 copyright date.

The software worked well with very large records sets but testing showed some circumstances caused data corruption. For example, file sizes over 700 MB were problematic. (Note that most hard disks were smaller than 700 MB at the time this was in wide use). The Getting Started manual warns about a number of circumstances where obsolete device drivers or incorrect configurations can cause data loss.

MS-Access's initial codename was Cirrus. This was developed before Visual Basic and the forms engine was called Ruby.

Bill Gates saw the protoypes and decided that the Basic language component should be co-developed as a separate expandable application. This project was called Thunder.

The two projects were developed separately as the underlying forms engines were incompatible with each other; however, these were merged together again after VBA.


Microsoft Access Usage

Access is widely used by small businesses, within departments of large corporations, and hobby programmers to create ad hoc customized systems for handling the creation and manipulation of data. Its ease of use and powerful design tools give the non-professional programmer a lot of power for little effort. However, this ease of use can be misleading. This sort of developer is often an office worker with little or no training in application or data design. Because Access makes it possible even for such developers to create usable systems, many are misled into thinking that the tool itself is limited to such applications.

Some professional application developers use Access for rapid application development, especially for the creation of prototypes and standalone applications that serve as tools for on-the-road salesmen. Access does not scale well if data access is via a network, so applications that are used by more than a handful of people tend to rely on a Client-Server based solution such as Oracle, DB2, Microsoft SQL Server, PostgreSQL, MySQL, MaxDB, or FileMaker. However, an Access "front end" (the forms, reports, queries and VB code) can be used against a host of database backends, including Access itself, Microsoft SQL Server, Oracle, and any other ODBC-compliant product. This approach allows the developer to move a matured application's data to a more powerful server without sacrificing the development already in place.

Many developers who use Microsoft Access use the Leszynski naming convention, though this is not universal; it is a programming convention, not a DBMS-enforced rule.


Microsoft Access Features

One of the benefits of Access from a programmer's perspective is its relative compatibility with SQL – queries may be viewed and edited as SQL statements, and SQL statements can be used directly in Macros and VBA Modules to manipulate Access tables. Users may mix and use both VBA and "Macros" for programming forms and logic and offers object-oriented possibilities.

The report writer in Access is capable and up to the task of sophisticated report creation. MSDE (Microsoft SQL Server Desktop Engine) 2000, a mini-version of MS SQL Server 2000, is included with the developer edition of Office XP and may be used with Access as an alternative to the Jet Database Engine.

The Access cut-and-paste functionality can make it a useful tool for connecting between other databases (for example, Oracle and Microsoft SQL Server during data or database conversions). Access comes with various import and export features that allow integration with Windows and other platform applications, several of which can be executed on demand from within applications or manually by the user. For example the very compact SNP format for sharing perfectly formatted reports with people who don't have the full Access software. It can also easily be upgraded to Microsoft SQL Server.

Unlike a complete RDBMS, the Jet Engine lacks database triggers and stored procedures. Starting in MS Access 2000 (Jet 4.0), there is a syntax that allows creating queries with parameters, in a way that looks like creating stored procedures, but these procedures are limited to one statement per procedure.[1] Microsoft Access does allow forms to contain code that is triggered as changes are made to the underlying table (as long as the modifications are done only with that form), and it is common to use pass-through queries and other techniques in Access to run stored procedures in RDBMSs that support these.

In ADP files (supported in MS Access 2000 and later), the database-related features are entirely different, because this type of file connects to a MSDE or Microsoft SQL Server, instead of using the Jet Engine. Thus, it supports the creation of nearly all objects in the underlying server (tables with constraints and triggers, views, stored procedures and UDF-s). However, only forms, reports, macros and modules are stored in the ADP file (the other objects are stored in the back-end database).


Microsoft Access Development

The programming language available in Access is, as in other products of the Microsoft Office suite, Microsoft Visual Basic for Applications. Two database access libraries of COM components are provided: the legacy Data Access Objects (DAO), only available with Access, and the new ActiveX Data Objects (ADO).

Microsoft Access is easily applied to small projects but scales poorly to large projects owing to weak security and database locking features.

All database queries, forms, and reports are stored in the database, and in keeping with the ideals of the relational model, there is no possibility of making a physically structured hierarchy with them.

One design technique is to divide an Access application between data and programs. One database should contain only tables and relationships, while another would have all programs, forms, reports and queries, and links to the first database tables. Unfortunately, Access allows no relative paths when linking, so the development environment should have the same path as the production environment (Although you can write your own "dynamic-linker" routine in VBA that can search out a certain back-end file by searching through the directory tree, if it can't find it in the current path).

This technique also allows the developer to divide the application among different files, so some structure is possible.

ACCESS Co., Ltd.

ACCESS Co., Ltd. (ACCESS Kabushiki-gaisha Akusesu) (TYO: 4813 ), founded in 1984 in Tokyo, Japan, is a company providing embedded software for connected devices, such as mobile phones, PDAs, video game consoles and set top boxes.

The company gained wide recognition for its NetFront browser product, which has been deployed in over 200 Million devices as of November 2005 (See: http://www.access-us-inc.com/news_releases/20051122a.html), and has been used as a principal element of the widely successful i-mode data service of NTT DoCoMo in Japan. It is also in use by the Sony PSP as the web browser for versions 2.0 and above.

In September 2005, ACCESS has acquired PalmSource, the owners of the Palm OS and BeOS.

ACCESS.bus

ACCESS.bus (or A.b) is a peripheral-interconnect computer bus developed by Philips in the early 1990s. It is similar in purpose to USB, in that it allows low-speed devices to be added or removed from a computer on the fly. While it was in use earlier than USB, it never became popular, largely due to considerably less corporate backing in the industry.

A.b is a physical layer definition that describes the physical cabling and connectors used in the network. The higher layers, namely the signaling and protocol issues, are already defined to be the same as Philips' I²C bus.

Compared to I²C, A.b:

adds two additional pins to provide power to the devices (+5 V and GND)
allows for only 125 devices out of I²C's 1024
supports only the 100 kbit/s "standard mode" and 10 kbit/s "low-speed mode"
The idea was to define a single standard that could be used both inside and outside a computer. A single I²C/A.b controller chip would be used inside the machine, connected on the motherboard to internal devices like the clock and battery power monitor. An A.b connector on the outside would then allow additional devices to be plugged into the bus. This way all of the low- and medium-speed devices on the machine would be driven by a single controller and protocol stack.

A.b also defined a small set of standardized device classes. These included monitors, keyboards, "locators" (pointing devices like mice and joysticks), battery monitors, and "text devices" (modems, etc.). Depending on how much intelligence the device needed, the interface in the device could leave almost all of the work to the driver. This allows A.b to scale down to price points low enough for devices like mice.

Although A.b mice and keyboards have been available (in limited fashion) for some time, the only serious attempt to use the system was by the VESA group. They needed a standardized bus for communicating device abilities between monitors and computers, and selected I²C because it required only two pins. Re-using existing "reserved" pins in the standard VGA connector allows for a complete A.b implementation (including power). A number of monitors with A.b connectors started appearing in the mid-1990s, but this was at about the same time USB was being created. So while many still use the system to communicate to the graphics card, few (if any) include the A.b connector.

Compared to USB, A.b has several advantages. One is that any device on the bus can be a master or a slave, and a protocol is defined for selecting which one a device should use under any particular circumstance. This allows devices to be plugged together with A.b without any computer. For instance, a digital camera could be plugged directly into a printer and become the master. Under USB the computer is always the master and the devices are always slaves. In order to support the same sort of device-to-device connection, USB requires additional support in the dual role OTG devices, to emulate a host and provide similar functionality (although higher data rates). Another advantage of A.b is that devices can be strung together into a single daisy-chain—A.b can support, but does not require, the use of hubs. This can reduce cable-clutter significantly.

On the downside, A.b is much slower than USB. Had IEEE 1394 (also known as FireWire) been widely available at the time, a computer with both A.b and FireWire would have been an attractive solution for all speed ranges. As it was, USB fit neatly into the niche between the two. With USB soon included in the standard motherboard control chips from Intel, A.b was pushed out onto the low-end and quickly disappeared.