Computer data storage
Computer data storage called storage or memory, is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers; the central processing unit of a computer is. In practice all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but larger and cheaper options farther away; the fast volatile technologies are referred to as "memory", while slower persistent technologies are referred to as "storage". In the Von Neumann architecture, the CPU consists of two main parts: The control unit and the arithmetic logic unit; the former controls the flow of data between the CPU and memory, while the latter performs arithmetic and logical operations on data. Without a significant amount of memory, a computer would be able to perform fixed operations and output the result, it would have to be reconfigured to change its behavior. This is acceptable for devices such as desk calculators, digital signal processors, other specialized devices.
Von Neumann machines differ in having a memory in which they store their operating instructions and data. Such computers are more versatile in that they do not need to have their hardware reconfigured for each new program, but can be reprogrammed with new in-memory instructions. Most modern computers are von Neumann machines. A modern digital computer represents data using the binary numeral system. Text, pictures and nearly any other form of information can be converted into a string of bits, or binary digits, each of which has a value of 1 or 0; the most common unit of storage is the byte, equal to 8 bits. A piece of information can be handled by any computer or device whose storage space is large enough to accommodate the binary representation of the piece of information, or data. For example, the complete works of Shakespeare, about 1250 pages in print, can be stored in about five megabytes with one byte per character. Data are encoded by assigning a bit pattern to digit, or multimedia object.
Many standards exist for encoding. By adding bits to each encoded unit, redundancy allows the computer to both detect errors in coded data and correct them based on mathematical algorithms. Errors occur in low probabilities due to random bit value flipping, or "physical bit fatigue", loss of the physical bit in storage of its ability to maintain a distinguishable value, or due to errors in inter or intra-computer communication. A random bit flip is corrected upon detection. A bit, or a group of malfunctioning physical bits is automatically fenced-out, taken out of use by the device, replaced with another functioning equivalent group in the device, where the corrected bit values are restored; the cyclic redundancy check method is used in communications and storage for error detection. A detected error is retried. Data compression methods allow in many cases to represent a string of bits by a shorter bit string and reconstruct the original string when needed; this utilizes less storage for many types of data at the cost of more computation.
Analysis of trade-off between storage cost saving and costs of related computations and possible delays in data availability is done before deciding whether to keep certain data compressed or not. For security reasons certain types of data may be kept encrypted in storage to prevent the possibility of unauthorized information reconstruction from chunks of storage snapshots; the lower a storage is in the hierarchy, the lesser its bandwidth and the greater its access latency is from the CPU. This traditional division of storage to primary, secondary and off-line storage is guided by cost per bit. In contemporary usage, "memory" is semiconductor storage read-write random-access memory DRAM or other forms of fast but temporary storage. "Storage" consists of storage devices and their media not directly accessible by the CPU hard disk drives, optical disc drives, other devices slower than RAM but non-volatile. Memory has been called core memory, main memory, real storage or internal memory. Meanwhile, non-volatile storage devices have been referred to as secondary storage, external memory or auxiliary/peripheral storage.
Primary storage referred to as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions executes them as required. Any data operated on is stored there in uniform manner. Early computers used delay lines, Williams tubes, or rotating magnetic drums as primary storage. By 1954, those unreliable methods were replaced by magnetic core memory. Core memory remained dominant until the 1970s, when advances in integrated circuit technology allowed semiconductor memory to become economically competitive; this led to modern random-access memo
A package manager or package-management system is a collection of software tools that automates the process of installing, upgrading and removing computer programs for a computer's operating system in a consistent manner. A package manager deals with distributions of software and data in archive files. Packages contain metadata, such as the software's name, description of its purpose, version number, checksum, a list of dependencies necessary for the software to run properly. Upon installation, metadata is stored in a local package database. Package managers maintain a database of software dependencies and version information to prevent software mismatches and missing prerequisites, they work with software repositories, binary repository managers, app stores. Package managers are designed to eliminate the need for manual updates; this can be useful for large enterprises whose operating systems are based on Linux and other Unix-like systems consisting of hundreds or tens of thousands of distinct software packages.
A software package is an archive file containing a computer program as well as necessary metadata for its deployment. The computer program can be in source code that has to be built first. Package metadata include package description, package version, dependencies. Package managers are charged with the task of finding, maintaining or uninstalling software packages upon the user's command. Typical functions of a package management system include: Working with file archivers to extract package archives Ensuring the integrity and authenticity of the package by verifying their digital certificates and checksums Looking up, installing or updating existing software from a software repository or app store Grouping packages by function to reduce user confusion Managing dependencies to ensure a package is installed with all packages it requires, thus avoiding "dependency hell" Computer systems that rely on dynamic library linking, instead of static library linking, share executable libraries of machine instructions across packages and applications.
In these systems, complex relationships between different packages requiring different versions of libraries results in a challenge colloquially known as "dependency hell". On Microsoft Windows systems, this is called "DLL hell" when working with dynamically linked libraries. Good package management is vital on these systems; the Framework system from OPENSTEP was an attempt at solving this issue, by allowing multiple versions of libraries to be installed and for software packages to specify which version they were linked against. System administrators may install and maintain software using tools other than package management software. For example, a local administrator may download unpackaged source code, compile it, install it; this may cause the state of the local system to fall out of synchronization with the state of the package manager's database. The local administrator will be required to take additional measures, such as manually managing some dependencies or integrating the changes into the package manager.
There are tools available to ensure that locally compiled packages are integrated with the package management. For distributions based on.deb and.rpm files as well as Slackware Linux, there is CheckInstall, for recipe-based systems such as Gentoo Linux and hybrid systems such as Arch Linux, it is possible to write a recipe first, which ensures that the package fits into the local package database. Troublesome with software upgrades are upgrades of configuration files. Since package managers, at least on Unix systems, originated as extensions of file archiving utilities, they can only either overwrite or retain configuration files, rather than applying rules to them. There are exceptions to this that apply to kernel configuration. Problems can be caused; some package managers, such as Debian's dpkg, allow configuration during installation. In other situations, it is desirable to install packages with the default configuration and overwrite this configuration, for instance, in headless installations to a large number of computers.
This kind of pre-configured installation is supported by dpkg. To give users more control over the kinds of software that they are allowing to be installed on their system, software is downloaded from a number of software repositories; when a user interacts with the package management software to bring about an upgrade, it is customary to present the user with the list of actions to be executed, allow the user to either accept the upgrade in bulk, or select individual packages for upgrades. Many package managers can be configured to never upgrade certain packages, or to upgrade them only when critical vulnerabilities or instabilities are found in the previous version, as defined by the packager of the software; this process is sometimes called version pinning. For instance: yum supports this with the syntax exclude=openoffice* pacman with IgnorePkg = openoffice dpkg and dselect support this through the hold flag in package selections APT extends the hold flag through the complex "pinning" mechanismUsers can blacklist a package aptitude has "hold" and "forbid" flags portage s
Ipfirewall or ipfw is a FreeBSD IP, stateful firewall, packet filter and traffic accounting facility. Its ruleset logic is similar to many other packet filters except IPFilter. Ipfw is maintained by FreeBSD volunteer staff members, its syntax enables use of sophisticated filtering capabilities and thus enables users to satisfy advanced requirements. It can either be incorporated into the kernel. Ipfw was the built-in firewall of Mac OS X until Mac OS X 10.7 Lion in 2011 when it was replaced with the OpenBSD project's PF. Like FreeBSD, ipfw is open source, it is used in many FreeBSD-based firewall products, including m0n0wall and FreeNAS. A port of ipfw and the dummynet traffic shaper is available for Linux, OpenWrt and Microsoft Windows. Wipfw is a Windows port of an old version of ipfw. netfilter/iptables, a Linux-based descendant of ipchains NPF, a NetBSD packet filter PF, another deployed BSD firewall solution ipfw section of the FreeBSD Handbook. The dummynet project - including versions for Linux, OpenWrt and Windows wipfw Windows port of an old version of ipfw
Boulder Creek, California
Boulder Creek is a census-designated place in Santa Cruz County, with a population of 4,923 as of the 2010 census. It is named for Boulder Creek. Boulder Creek served as the upper terminus of the San Lorenzo Valley Logging Flume terminating in Felton, which began construction in 1874 and when formally opened in October 1875 was augmented by a new rail line to transport logs to the wharf in Santa Cruz. In the 1880s, this lumber town, called Lorenzo took the name of the Boulder Creek post office, established in the 1870s. Boulder Creek is located at 37°7′30″N 122°7′30″W. According to the United States Census Bureau, the CDP has a total area of 7.5 square miles. Boulder Creek is the gateway town to Big Basin Redwoods State Park, California's oldest State Park, founded in 1902; the 2010 United States Census reported that Boulder Creek had a population of 4,923. The population density was 655.4 people per square mile. The racial makeup of Boulder Creek was 4,429 White, 54 African American, 31 Native American, 81 Asian, 5 Pacific Islander, 119 from other races, 204 from two or more races.
Hispanic or Latino of any race were 366 persons. The Census reported. There were 2,124 households, out of which 548 had children under the age of 18 living in them, 997 were opposite-sex married couples living together, 176 had a female householder with no husband present, 97 had a male householder with no wife present. There were 189 unmarried opposite-sex partnerships, 29 same-sex married couples or partnerships. 598 households were made up of individuals and 129 had someone living alone, 65 years of age or older. The average household size was 2.32. There were 1,270 families; the population was spread out with 884 people under the age of 18, 319 people aged 18 to 24, 1,222 people aged 25 to 44, 2,066 people aged 45 to 64, 432 people who were 65 years of age or older. The median age was 45.4 years. For every 100 females, there were 105.2 males. For every 100 females age 18 and over, there were 104.3 males. There were 2,455 housing units at an average density of 326.8 per square mile, of which 71.6% were owner-occupied and 28.4% were occupied by renters.
The homeowner vacancy rate was 2.1%. 74.0% of the population lived in owner-occupied housing units and 26.0% lived in rental housing units. As of the census of 2000, there were 4,081 people, 1,630 households, 1,025 families residing in the CDP; the population density was 963.3 people per square mile. There were 1,829 housing units at an average density of 431.7 per square mile. The racial makeup of the CDP was 90.25% White, 0.59% African American, 1.10% Native American, 1.72% Asian, 0.20% Pacific Islander, 2.18% from other races, 3.97% from two or more races. Hispanic or Latino of any race were 5.68% of the population. There were 1,630 households, of which 31.8% had children under the age of 18 living with them, 48.1% were married couples living together, 10.1% had a female householder with no husband present, 37.1% were non-families. 25.6% of all households were made up of individuals and 4.2% had someone living alone, 65 years of age or older. The average household size was 2.50 and the average family size was 3.02.
In the CDP, the population was spread out with 23.6% under the age of 18, 7.9% from 18 to 24, 33.8% from 25 to 44, 28.7% from 45 to 64, 6.0% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 101.1 males. For every 100 females age 18 and over, there were 101.6 males. The median income for a household in the CDP was $60,455, the median income for a family was $66,037. Males had a median income of $48,125 versus $40,197 for females; the per capita income for the CDP was $32,012. About 1.9% of families and 8.0% of the population were below the poverty line, including 0.9% of those under age 18 and 7.4% of those age 65 or over. In the California State Legislature, Boulder Creek is in the 17th Senate District, represented by Democrat Bill Monning, in the 29th Assembly District, represented by Democrat Mark Stone. In the United States House of Representatives, Boulder Creek is in California's 18th congressional district, represented by Democrat Anna Eshoo.
The Boulder Creek area is represented on the Santa Cruz County Board of Supervisors by Bruce McPherson. Cora Evans, Catholic mystic Jonathan Franzen, author Nick Herbert, poet, author Jordan Hubbard, technologist and co-founder of FreeBSD Welcome to Boulder-Creek.com Santa Cruz Mountain Bulletin - Newspaper - reporting news for San Lorenzo Valley and all of the Santa Cruz Mountains Boulder Creek Insider - Community blog - Commentary and Current Events
University of California, Berkeley
The University of California, Berkeley is a public research university in Berkeley, California. It was founded in 1868 and serves as the flagship institution of the ten research universities affiliated with the University of California system. Berkeley has since grown to instruct over 40,000 students in 350 undergraduate and graduate degree programs covering numerous disciplines. Berkeley is one of the 14 founding members of the Association of American Universities, with $789 million in R&D expenditures in the fiscal year ending June 30, 2015. Today, Berkeley maintains close relationships with three United States Department of Energy National Laboratories—Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory and Los Alamos National Laboratory—and is home to many institutes, including the Mathematical Sciences Research Institute and the Space Sciences Laboratory. Through its partner institution University of California, San Francisco, Berkeley offers a joint medical program at the UCSF Medical Center.
As of October 2018, Berkeley alumni, faculty members and researchers include 107 Nobel laureates, 25 Turing Award winners, 14 Fields Medalists. They have won 9 Wolf Prizes, 45 MacArthur Fellowships, 20 Academy Awards, 14 Pulitzer Prizes and 207 Olympic medals. In 1930, Ernest Lawrence invented the cyclotron at Berkeley, based on which UC Berkeley researchers along with Berkeley Lab have discovered or co-discovered 16 chemical elements of the periodic table – more than any other university in the world. During the 1940s, Berkeley physicist J. R. Oppenheimer, the "Father of the Atomic Bomb," led the Manhattan project to create the first atomic bomb. In the 1960s, Berkeley was noted for the Free Speech Movement as well as the Anti-Vietnam War Movement led by its students. In the 21st century, Berkeley has become one of the leading universities in producing entrepreneurs and its alumni have founded a large number of companies worldwide. Berkeley is ranked among the top 20 universities in the world by the Academic Ranking of World Universities, the Times Higher Education World University Rankings, the U.
S. News & World Report Global University Rankings, it is considered one of the "Public Ivies", meaning that it is a public university thought to offer a quality of education comparable to that of the Ivy League. In 1866, the private College of California purchased the land comprising the current Berkeley campus in order to re-sell it in subdivided lots to raise funds; the effort failed to raise the necessary funds, so the private college merged with the state-run Agricultural and Mechanical Arts College to form the University of California, the first full-curriculum public university in the state. Upon its founding, The Dwinelle Bill stated that the "University shall have for its design, to provide instruction and thorough and complete education in all departments of science and art, industrial and professional pursuits, general education, special courses of instruction in preparation for the professions". Ten faculty members and 40 students made up the new University of California when it opened in Oakland in 1869.
Frederick H. Billings was a trustee of the College of California and suggested that the new site for the college north of Oakland be named in honor of the Anglo-Irish philosopher George Berkeley. In 1870, Henry Durant, the founder of the College of California, became the first president. With the completion of North and South Halls in 1873, the university relocated to its Berkeley location with 167 male and 22 female students where it held its first classes. Beginning in 1891, Phoebe Apperson Hearst made several large gifts to Berkeley, funding a number of programs and new buildings and sponsoring, in 1898, an international competition in Antwerp, where French architect Émile Bénard submitted the winning design for a campus master plan. In 1905, the University Farm was established near Sacramento becoming the University of California, Davis. In 1919, Los Angeles State Normal School became the southern branch of the University, which became University of California, Los Angeles. By 1920s, the number of campus buildings had grown and included twenty structures designed by architect John Galen Howard.
Robert Gordon Sproul served as president from 1930 to 1958. In the 1930s, Ernest Lawrence helped establish the Radiation Laboratory and invented the cyclotron, which won him the Nobel physics prize in 1939. Based on the cyclotron, UC Berkeley scientists and researchers, along with Berkeley Lab, went on to discover 16 chemical elements of the periodic table – more than any other university in the world. In particular, during World War II and following Glenn Seaborg's then-secret discovery of plutonium, Ernest Orlando Lawrence's Radiation Laboratory began to contract with the U. S. Army to develop the atomic bomb. UC Berkeley physics professor J. Robert Oppenheimer was named scientific head of the Manhattan Project in 1942. Along with the Lawrence Berkeley National Laboratory, Berkeley was a partner in managing two other labs, Los Alamos National Laboratory and Lawrence Livermore National Laboratory. By 1942, the American Council on Education ranked Berkeley second only to Harvard in the number of distinguished departments.
During the McCarthy era in 1949, the Board of Regents adopted an anti-communist loyalty oath. A number of faculty members led by Edward C. Tolman were dismissed. In 1952, the University of California became; each campus was give
Purdue University is a public research university in West Lafayette and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money to establish a college of science and agriculture in his name; the first classes were held on September 1874, with six instructors and 39 students. The main campus in West Lafayette offers more than 200 majors for undergraduates, over 69 masters and doctoral programs, professional degrees in pharmacy and veterinary medicine. In addition, Purdue has more than 900 student organizations. Purdue is a member of the Big Ten Conference and enrolls the second largest student body of any university in Indiana, as well as the fourth largest foreign student population of any university in the United States. In 1865, the Indiana General Assembly voted to take advantage of the Morrill Land-Grant Colleges Act of 1862, began plans to establish an institution with a focus on agriculture and engineering.
Communities throughout the state offered their facilities and money to bid for the location of the new college. Popular proposals included the addition of an agriculture department at Indiana State University or at what is now Butler University. By 1869, Tippecanoe County’s offer included $150,000 from Lafayette business leader and philanthropist John Purdue, $50,000 from the county, 100 acres of land from local residents. On May 6, 1869, the General Assembly established the institution in Tippecanoe County as Purdue University, in the name of the principal benefactor. Classes began at Purdue on September 1874, with six instructors and 39 students. Professor John S. Hougham was Purdue’s first faculty member and served as acting president between the administrations of presidents Shortridge and White. A campus of five buildings was completed by the end of 1874. Purdue issued its first degree, a Bachelor of Science in chemistry, in 1875 and admitted its first female students that fall. Emerson E. White, the university’s president from 1876 to 1883, followed a strict interpretation of the Morrill Act.
Rather than emulate the classical universities, White believed Purdue should be an "industrial college" and devote its resources toward providing a liberal education with an emphasis on science and agriculture. He intended not only to prepare students for industrial work, but to prepare them to be good citizens and family members. Part of White's plan to distinguish Purdue from classical universities included a controversial attempt to ban fraternities; this ban was overturned by the Indiana Supreme Court and led to White's resignation. The next president, James H. Smart, is remembered for his call in 1894 to rebuild the original Heavilon Hall "one brick higher" after it had been destroyed by a fire. By the end of the nineteenth century, the university was organized into schools of agriculture and pharmacy, former U. S. President Benjamin Harrison was serving on the board of trustees. Purdue's engineering laboratories included testing facilities for a locomotive and a Corliss steam engine, one of the most efficient engines of the time.
The School of Agriculture was sharing its research with farmers throughout the state with its cooperative extension services and would undergo a period of growth over the following two decades. Programs in education and home economics were soon established, as well as a short-lived school of medicine. By 1925 Purdue had the largest undergraduate engineering enrollment in the country, a status it would keep for half a century. President Edward C. Elliott oversaw a campus building program between the world wars. Inventor and trustee David E. Ross coordinated several fundraisers, donated lands to the university, was instrumental in establishing the Purdue Research Foundation. Ross's gifts and fundraisers supported such projects as Ross–Ade Stadium, the Memorial Union, a civil engineering surveying camp, Purdue University Airport. Purdue Airport was the country's first university-owned airport and the site of the country's first college-credit flight training courses. Amelia Earhart joined the Purdue faculty in 1935 as a consultant for these flight courses and as a counselor on women's careers.
In 1937, the Purdue Research Foundation provided the funds for the Lockheed Electra 10-E Earhart flew on her attempted round-the-world flight. Every school and department at the university was involved in some type of military research or training during World War II. During a project on radar receivers, Purdue physicists discovered properties of germanium that led to the making of the first transistor; the Army and the Navy conducted training programs at Purdue and more than 17,500 students and alumni served in the armed forces. Purdue set up about a hundred centers throughout Indiana to train skilled workers for defense industries; as veterans returned to the university under the G. I. Bill, first-year classes were taught at some of these sites to alleviate the demand for campus space. Four of these sites are now degree-granting regional campuses of the Purdue University system. Purdue's on-campus housing became racially desegregated in 1947, following pressure from Purdue President Frederick L. Hovde and Indiana Governor Ralph F. Gates.
After the war, Hovde worked to expand the academic opportunities at the university. A decade-long construction program emphasized research. In the late 1950s and early 1960s the university established programs in veterinary medicine, industrial management, nursing, as well as the first computer science department in the United States. Undergraduate humanities courses were strengthened
University of Texas at Austin
The University of Texas at Austin is a public research university in Austin, Texas. It is the flagship institution of the University of Texas System; the University of Texas was inducted into the Association of American Universities in 1929, becoming only the third university in the American South to be elected. The institution has the nation's eighth-largest single-campus enrollment, with over 50,000 undergraduate and graduate students and over 24,000 faculty and staff. A Public Ivy, it is a major center for academic research, with research expenditures exceeding $615 million for the 2016–2017 school year; the university houses seven museums and seventeen libraries, including the Lyndon Baines Johnson Library and Museum and the Blanton Museum of Art, operates various auxiliary research facilities, such as the J. J. Pickle Research Campus and the McDonald Observatory. Among university faculty are recipients of the Nobel Prize, Pulitzer Prize, the Wolf Prize, the Primetime Emmy Award, the Turing Award, the National Medal of Science, as well as many other awards.
As of October 2018, 11 Nobel Prize winners, 2 Turing Award winners and 1 Fields medalist have been affiliated with the school as alumni, faculty members or researchers. Student athletes are members of the Big 12 Conference, its Longhorn Network is the only sports network featuring the college sports of a single university. The Longhorns have won four NCAA Division I National Football Championships, six NCAA Division I National Baseball Championships, thirteen NCAA Division I National Men's Swimming and Diving Championships, has claimed more titles in men's and women's sports than any other school in the Big 12 since the league was founded in 1996; the first mention of a public university in Texas can be traced to the 1827 constitution for the Mexican state of Coahuila y Tejas. Although Title 6, Article 217 of the Constitution promised to establish public education in the arts and sciences, no action was taken by the Mexican government. After Texas obtained its independence from Mexico in 1836, the Texas Congress adopted the Constitution of the Republic, under Section 5 of its General Provisions, stated "It shall be the duty of Congress, as soon as circumstances will permit, to provide, by law, a general system of education."On April 18, 1838, "An Act to Establish the University of Texas" was referred to a special committee of the Texas Congress, but was not reported back for further action.
On January 26, 1839, the Texas Congress agreed to set aside fifty leagues of land—approximately 288,000 acres —towards the establishment of a publicly funded university. In addition, 40 acres in the new capital of Austin were reserved and designated "College Hill." In 1845, Texas was annexed into the United States. The state's Constitution of 1845 failed to mention higher education. On February 11, 1858, the Seventh Texas Legislature approved O. B. 102, an act to establish the University of Texas, which set aside $100,000 in United States bonds toward construction of the state's first publicly funded university. The legislature designated land reserved for the encouragement of railroad construction toward the university's endowment. On January 31, 1860, the state legislature, wanting to avoid raising taxes, passed an act authorizing the money set aside for the University of Texas to be used for frontier defense in west Texas to protect settlers from Indian attacks. Texas's secession from the Union and the American Civil War delayed repayment of the borrowed monies.
At the end of the Civil War in 1865, The University of Texas's endowment was just over $16,000 in warrants and nothing substantive had been done to organize the university's operations. This effort to establish a University was again mandated by Article 7, Section 10 of the Texas Constitution of 1876 which directed the legislature to "establish and provide for the maintenance and direction of a university of the first class, to be located by a vote of the people of this State, styled "The University of Texas."Additionally, Article 7, Section 11 of the 1876 Constitution established the Permanent University Fund, a sovereign wealth fund managed by the Board of Regents of the University of Texas and dedicated for the maintenance of the university. Because some state legislators perceived an extravagance in the construction of academic buildings of other universities, Article 7, Section 14 of the Constitution expressly prohibited the legislature from using the state's general revenue to fund construction of university buildings.
Funds for constructing university buildings had to come from the university's endowment or from private gifts to the university, but the university's operating expenses could come from the state's general revenues. The 1876 Constitution revoked the endowment of the railroad lands of the Act of 1858, but dedicated 1,000,000 acres of land, along with other property appropriated for the university, to the Permanent University Fund; this was to the detriment of the university as the lands the Constitution of 1876 granted the university represented less than 5% of the value of the lands granted to the university under the Act of 1858. The more valuable lands reverted to the fund to support general educat