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Topic Review
Pax (Command)
Pax is an archiving utility available for various operating systems and defined since 1995. Rather than sort out the incompatible options that have crept up between tar and cpio, along with their implementations across various versions of Unix, the IEEE designed new archive utility pax that could support various archive formats with useful options from both archivers. The pax command is available on Unix and Unix-like operating systems and on IBM i, Microsoft Windows NT, and Windows 2000. In 2001, IEEE defined a new pax format which is basically tar with additional extended attributes. The format is not supported by pax commands in most Linux distributions and in FreeBSD, but it is supported by tar commands from GNU and FreeBSD; the format is further supported by pax commands in AIX, Solaris and HP-UX. The name "pax" is an acronym for portable archive exchange. The command invocation and structure is somewhat a unification of both tar and cpio.
  • 649
  • 04 Nov 2022
Topic Review
Pipeline
In software engineering, a pipeline consists of a chain of processing elements (processes, threads, coroutines, functions, etc.), arranged so that the output of each element is the input of the next; the name is by analogy to a physical pipeline. Usually some amount of buffering is provided between consecutive elements. The information that flows in these pipelines is often a stream of records, bytes, or bits, and the elements of a pipeline may be called filters; this is also called the pipes and filters design pattern. Connecting elements into a pipeline is analogous to function composition. Narrowly speaking, a pipeline is linear and one-directional, though sometimes the term is applied to more general flows. For example, a primarily one-directional pipeline may have some communication in the other direction, known as a return channel or backchannel, as in the lexer hack, or a pipeline may be fully bi-directional. Flows with one-directional tree and directed acyclic graph topologies behave similarly to (linear) pipelines – the lack of cycles makes them simple – and thus may be loosely referred to as "pipelines".
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Topic Review
Amazon Elastic Compute Cloud
Amazon Elastic Compute Cloud (EC2) is a part of Amazon.com's cloud-computing platform, Amazon Web Services (AWS), that allows users to rent virtual computers on which to run their own computer applications. EC2 encourages scalable deployment of applications by providing a web service through which a user can boot an Amazon Machine Image (AMI) to configure a virtual machine, which Amazon calls an "instance", containing any software desired. A user can create, launch, and terminate server-instances as needed, paying by the second for active servers – hence the term "elastic". EC2 provides users with control over the geographical location of instances that allows for latency optimization and high levels of redundancy. In November 2010, Amazon switched its own retail website platform to EC2 and AWS.
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  • 04 Nov 2022
Topic Review
Halt and Catch Fire
In computer engineering, Halt and Catch Fire, known by the assembly mnemonic HCF, is an idiom referring to a computer machine code instruction that causes the computer's central processing unit (CPU) to cease meaningful operation, typically requiring a restart of the computer. It originally referred to a fictitious instruction in IBM System/360 computers, making a joke about its numerous non-obvious instruction mnemonics. With the advent of the MC6800, a design flaw was discovered by the programmers. Due to incomplete opcode decoding, two illegal opcodes, 0x9D and 0xDD, will cause the program counter on the processor to increment endlessly, which renders the processor useless. Those codes have been unofficially named HCF. During the design process of MC6802, engineers originally planned to remove this instruction, but kept it as-is for testing purposes. As a result, HCF was officially recognized as a real instruction. Later, HCF became a humorous catch-all term for instructions that may freeze a processor, including intentional instructions for testing purposes, and unintentional illegal instructions. Some are considered hardware defects, and if the system is shared, a malicious user can execute it to launch a denial-of-service attack. In the case of real instructions, the implication of this expression is that, whereas in most cases in which a CPU executes an unintended instruction (a bug in the code) the computer may still be able to recover, in the case of an HCF instruction there is, by definition, no way for the system to recover without a restart. The expression "catch fire" is a facetious exaggeration of the speed with which the CPU chip would be switching some bus circuits, causing them to overheat and burn.
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  • 04 Nov 2022
Topic Review
Design Thinking
Design thinking is a term used to represent a set of cognitive, strategic and practical processes by which design concepts (proposals for products, buildings, machines, communications, etc.) are developed. Many of the key concepts and aspects of design thinking have been identified through studies, across different design domains, of design cognition and design activity in both laboratory and natural contexts. Design thinking is also associated with prescriptions for the innovation of products and services within business and social contexts. Some of these prescriptions have been criticized for oversimplifying the design process and trivializing the role of technical knowledge and skills.
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  • 04 Nov 2022
Topic Review
Abstract Syntax Notation One
Abstract Syntax Notation One (ASN.1) is a standard interface description language for defining data structures that can be serialized and deserialized in a cross-platform way. It is broadly used in telecommunications and computer networking, and especially in cryptography. Protocol developers define data structures in ASN.1 modules, which are generally a section of a broader standards document written in the ASN.1 language. The advantage is that the ASN.1 description of the data encoding is independent of a particular computer or programming language (other than ASN.1.) Because ASN.1 is both human-readable and machine-readable, an ASN.1 compiler can compile modules into libraries of code, CODECs, that decode or encode the data structures. Some ASN.1 compilers can produce code to encode or decode several encodings, e.g. packed, BER or XML. ASN.1 is a joint standard of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and ISO/IEC, originally defined in 1984 as part of CCITT X.409:1984. In 1988, ASN.1 moved to its own standard, X.208, due to wide applicability. The substantially revised 1995 version is covered by the X.680 series. The latest revision of the X.680 series of recommendations is the 5.0 Edition, published in 2015.
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Topic Review
Cartan Formalism
The vierbein or tetrad theory much used in theoretical physics is a special case of the application of Cartan connection in four-dimensional manifolds. It applies to metrics of any signature. (See metric tensor.) This section is an approach to tetrads, but written in general terms. In dimensions other than 4, words like triad, pentad, zweibein, fünfbein, elfbein etc. have been used. Vielbein covers all dimensions. (In German, vier means four, zwei means two, fünf means five, elf means eleven and, in general, viel means many.) For a basis-dependent index notation, see tetrad (index notation).
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Topic Review
Partition (Number Theory)
In number theory and combinatorics, a partition of a positive integer n, also called an integer partition, is a way of writing n as a sum of positive integers. Two sums that differ only in the order of their summands are considered the same partition. (If order matters, the sum becomes a composition.) For example, 4 can be partitioned in five distinct ways: 4 3 + 1 2 + 2 2 + 1 + 1 1 + 1 + 1 + 1 The order-dependent composition 1 + 3 is the same partition as 3 + 1, and the two distinct compositions 1 + 2 + 1 and 1 + 1 + 2 represent the same partition 2 + 1 + 1. A summand in a partition is also called a part. The number of partitions of n is given by the partition function p(n). So p(4) = 5. The notation λ ⊢ n means that λ is a partition of n. Partitions can be graphically visualized with Young diagrams or Ferrers diagrams. They occur in a number of branches of mathematics and physics, including the study of symmetric polynomials and of the symmetric group and in group representation theory in general.
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Topic Review
FUJITSU Cloud IaaS Trusted Public S5
FUJITSU Cloud IaaS Trusted Public S5 is a Fujitsu cloud computing platform that aims to deliver standardized enterprise-class public cloud services globally. It offers Infrastructure-as-a-Service (IaaS) from Fujitsu's data centres to provide computing resources that can be employed on-demand and suited to customers' needs. The service ensures a high level of reliability that is sufficient for deployment in mission-critical systems. In Japan, the service was offered as the On-Demand Virtual System Service (OViSS) and was then launched globally as Fujitsu Global Cloud Platform/S5 (FGCP/S5). Since July 2013 the service has been called IaaS Trusted Public S5. Globally, the service is operated from Fujitsu data centers located in Australia , Singapore, the United States , the United Kingdom and Germany . Fujitsu has also launched a Windows Azure powered Global Cloud Platform in a partnership with Microsoft. This is a Platform-as-a-Service (PaaS) offering that was known as FGCP/A5 in Japan but has since been renamed FUJITSU Cloud PaaS A5 for Windows Azure. It is operated from a Fujitsu data center in Japan. It offers a set of application development frameworks, such as Microsoft .NET, Java and PHP, and data storage capabilities consistent with the Windows Azure platform provided by Microsoft. The basic service consists of compute, storage, Microsoft SQL Azure, and Windows Azure AppFabric technologies such as Service Bus and Access Control Service, with options for interoperating services covering implementation and migration of applications, system building, systems operation, and support. In 2015, Fujitsu launched its next generation Cloud Service K5 and was deployed globally. In October 2018, Fujitsu announced that it was discontinuing K5 in all regions except Japan. On October 16, 2018 the company stated that it will hire 10,000 employees and train them to use Microsoft Azure in order to "address what we see as an industry-wide shortage in cloud related skills, so that we can help clients address their execution gap in the provision of services which support operational efficiency, digital co-creation and multi-cloud management.”
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Topic Review
First Order Arithmetic
In set theory and mathematical logic, first-order arithmetic is a collection of axiomatic systems formalising natural and subsets of the natural numbers. It is a choice for axiomatic theory as a basis for many mathematics, but not all. The primary first-order axiom is Peano arithmetic, created by Giuseppe Peano: Peano arithmetic has a proof-theoretic ordinal of [math]\displaystyle{ \varepsilon_0 = \varphi(1, 0) = \psi_0(\Omega) }[/math].
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