A block chain or blockchain is a permissionless distributed database based on the bitcoin protocol that maintains a continuously growing list of data records hardened against tampering and revision, even by its operators. The initial and most widely known application of block chain technology is the public ledger of transactions for bitcoin, which has been the inspiration for similar implementations often known as altchains.
The block chain consists of blocks that hold timestamped batches of recent valid transactions. Each block includes the hash of the prior block, linking the blocks together. The linked blocks form a chain, with each additional block reinforcing those before it, thus giving the database type its name.
A block chain implementation consists of two kinds of records: transactions and blocks.
Transactions are the content to be stored in the block chain.Transactions are created by participants using the system. In the case of cryptocurrencies, a transaction is created anytime a bitcoin owner sends cryptocurrency to another.
Chain was Edinburgh musician Paul Haig's third album and was released in May 1989 on Circa Records, a subsidiary of Virgin Records. Chain, which Haig financed himself, was recorded and completed in 1988, but it sat on the shelf after the normally accommodating Les Disques Du Crepuscule decided not to take up the option of releasing it. The album was co-produced by long-time Haig cohort, Alan Rankine, instrumentalist with celebrated Dundee band, The Associates. There was another Associates connection on the album - the track "Chained" was written by Haig's good friend, Billy Mackenzie. Haig returned the favour and gave Mackenzie the track "Reach The Top" for his album The Glamour Chase, which after many years in limbo was finally released in 2002.
One single, "Something Good", was taken from the album, but much to Circa's disappointment, neither the single nor the album sold in great numbers.
The Chain, sometimes also pronounced as Chai, are cultivating and fishing caste found in eastern Uttar Pradesh in India. They are a sub-group within the larger Kewat communinity of North India.
The Chai according to some traditions, were a community of Vaishyas, who lost caste, when they took to fishing. Other traditions make them out to be a branch of the Bindcaste, and the two communities intermarry, with suggests a common origin. They are now recognized as a sub-group within the Kewat community, and they intermarry with other Kewat clans such as the Banaphar and Dhivar. The majority of the Chai are now cultivators, with a small number still employed as boatmen on the Ganges. They are Hindu, and have customs similar to other Kewat groups.
A block of the periodic table of elements is a set of adjacent groups. The term appears to have been first used by Charles Janet. The respective highest-energy electrons in each element in a block belong to the same atomic orbital type. Each block is named after its characteristic orbital; thus, the blocks are:
The block names (s, p, d, f and g) are derived from the spectroscopic notation for the associated atomic orbitals: sharp, principal, diffuse and fundamental, and then g which follows f in the alphabet.
The following is the order for filling the "subshell" orbitals, according to the Aufbau principle, which also gives the linear order of the "blocks" (as atomic number increases) in the periodic table:
The "periodic" nature of the filling of orbitals, as well as emergence of the s, p, d and f "blocks" is more obvious, if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows ("periods") in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements:
Block is an Australian term for a small agricultural landholding. Block settlement has been used by Governments to encourage decentralization and during financial depressions to give families of unemployed workers an opportunity (frequently illusory) to become primary producers. It may also refer to a lifestyle choice or "hobby farm" for those with an independent source of income.
In parts of Australia, parcels of land of around 6 to 20 acres (2 to 8ha) were allocated by Government to working-class men at nominal rent during the depression of the 1890s with the object of giving them work and, potentially, a source of income. Some eventually prospered, but those on marginal land were doomed to failure. Proponents of the "block system" included George Witherage Cotton. Holders of such allotments were referred to as "blockers" or "blockies".
In computing (specifically data transmission and data storage), a block, sometimes called a physical record, is a sequence of bytes or bits, usually containing some whole number of records, having a maximum length, a block size. Data thus structured are said to be blocked. The process of putting data into blocks is called blocking, while deblocking is the process of extracting data from blocks. Blocked data is normally stored in a data buffer and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data-stream. For some devices such as magnetic tape and CKD disk devices blocking reduces the amount of external storage required for the data. Blocking is almost universally employed when storing data to 9-track magnetic tape, to NAND flash memory, and to rotating media such as floppy disks, hard disks, and optical discs.
Most file systems are based on a block device, which is a level of abstraction for the hardware responsible for storing and retrieving specified blocks of data, though the block size in file systems may be a multiple of the physical block size. This leads to space inefficiency due to internal fragmentation, since file lengths are often not integer multiples of block size, and thus the last block of a file may remain partially empty. This will create slack space, which averages half a block per file.
Some newer file systems attempt to solve this through techniques called block suballocation and tail merging.