Bootstrap
Bootstrap refers to the start-up of a computer. The term encompasses the loading of the operating system and other software necessary for the start-up phase. These operations occur when the computer is booted. A cold boot is when the computer is turned on from an off position. A warm boot is when a computer that is already running is reset.
The derivation of the term bootstrap is historical. Prior to the computer age, a bootstrap referred to the strap attached to the top of a boot, which could be used to pull the boot onto a foot. From this function arose the expression "pull oneself up by the bootstraps." As this bootstrap helped a person get ready, bootstrap utilities prepare a computer for operation.
Bootstrapping involves the implementation of the computer's operating system and the checking of all internal and peripheral devices to ensure that they are operational. If a device is found to be non-compliant, the start-up process is halted. A simple example is when a floppy disk has been left in its drive. Until the disk is removed and any key depressed, the start-up procedure is frozen.
To implement the operating system, the bootstrap program is loaded by the basic input/output system (BIOS). The BIOS is integral software that determines what a computer can do--functioning of the keyboard, display screen, disk drives, and serial communications--without accessing programs from a disk. The BIOS has no information concerning the environment required by the operating system; it merely initializes the system. It is the bootstrap program that loads the appropriate operating environment in which the operating system functions.
The bootstrap program is loaded from the first sector on a disk, which is called track zero, head zero, sector one. The program is very small, only 512 bytes. This 512-byte sector is loaded into memory at the physical address 0000:7000. The BIOS verifies that the bootstrap loading process has proceeded correctly, by examining the final two bytes for a designated value. Upon confirmation of loading, the BIOS jumps to the 0000:7000 address and turns the control of the start-up process over to the bootstrap.
Bootstrap also refers to a statistical method of analysis, created in 1977 by Stanford University statistician Bradley Efron. The method, which allows statisticians to determine the reliability of data analysis, requires the calculation muscle of computers to function. The method involves the construction of a new set of data by the computer, by the random selection of data from existing data. By analyzing how the newly generated data varies from the original set of data, the reliability of any inferences that were used in the original analysis can be probed. The method is called the bootstrap method because the data, in a sense, pull themselves up by their own bootstraps by generating the new data sets. Bootstrap analysis is relevant to many disciplines, ranging from medical to biological to sociological data analysis.
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