Good timing can be the difference between thousands of dollars in profits and absolutely zero. So here's the deal - I've written a unique FREE report for you... [LOGO]( At times, our affiliate partners reach out to the Editors at Non Stop Earnings with special opportunities for our readers. The message below is one we think you should take a close, serious look at. [Tim Plaehn's Book]( Stop! Before you read another email add this "forever dividend stock" to your income stream When I was flying F-16 jets as an Air Force captain, I learned the importance of timing. I'm sure you already know this - But if you want to be successful in life, you have to be good with timing. And investing is no different! Good timing can be the difference between thousands of dollars in profits and absolutely zero. So here's the deal - I've written a unique FREE report for you... [It will hand you the details about a specific dividend stock that pays you every month like clockwork.]( You can invest in it today, and potentially collect your first dividend check in as little as a couple of weeks. But, remember... Communicating systems History One of the first uses of the term protocol in a data-commutation context occurs in a memorandum entitled A Protocol for Use in the NPL Data Communications Network written by Roger Scantlebury and Keith Bartlett in April 1967.[5][6] On the ARPANET, the starting point for host-to-host communication in 1969 was the 1822 protocol, which defined the transmission of messages to an IMP.[7] The Network Control Protocol (NCP) for the ARPANET was first implemented in 1970.[8] The NCP interface allowed application software to connect across the ARPANET by implementing higher-level communication protocols, an early example of the protocol layering concept.[9] Networking research in the early 1970s by Robert E. Kahn and Vint Cerf led to the formulation of the Transmission Control Program (TCP).[10] Its RFC 675 specification was written by Cerf with Yogen Dalal and Carl Sunshine in December 1974, still a monolithic design at this time. The International Networking Working Group agreed a connectionless datagram standard which was presented to the CCIT in 1975 but was not adopted by the ITU or by the ARPANET.[11] International research, particularly the work of Rémi Després, contributed to the development of the X.25 standard, based on virtual circuits by the ITU-T in 1976.[12][13] Computer manufacturers developed proprietary protocols such as IBM's Systems Network Architecture (SNA), Digital Equipment Corporation's DECnet and Xerox Network Systems.[14] TCP software was redesigned as a modular protocol stack. Originally referred to as IP/TCP, it was installed on SATNET in 1982 and on the ARPANET in January 1983. The development of a complete protocol suite by 1989, as outlined in RFC 1122 and RFC 1123, laid the foundation for the growth of TCP/IP as a comprehensive protocol suite as the core component of the emerging Internet.[15] International work on a reference model for communication standards led to the OSI model, published in 1984. For a period in the late 1980s and early 1990s, engineers, organizations and nations became polarized over the issue of which standard, the OSI model or the Internet protocol suite, would result in the best and most robust computer networks.[16][17][18] Concept The information exchanged between devices through a network or other media is governed by rules and conventions that can be set out in communication protocol specifications. The nature of communication, the actual data exchanged and any state-dependent behaviors, is defined by these specifications. In digital computing systems, the rules can be expressed by algorithms and data structures. Protocols are to communication what algorithms or programming languages are to computations.[3][4] Operating systems usually contain a set of cooperating processes that manipulate shared data to communicate with each other. This communication is governed by well-understood protocols, which can be embedded in the process code itself.[19][20] In contrast, because there is no shared memory, communicating systems have to communicate with each other using a shared transmission medium. Transmission is not necessarily reliable, and individual systems may use different hardware or operating systems. To implement a networking protocol, the protocol software modules are interfaced with a framework implemented on the machine's operating system. This framework implements the networking functionality of the operating system.[21] When protocol algorithms are expressed in a portable programming language the protocol software may be made operating system independent. The best-known frameworks are the TCP/IP model and the OSI model. At the time the Internet was developed, abstraction layering had proven to be a successful design approach for both compiler and operating system design and, given the similarities between programming languages and communication protocols, the originally monolithic networking programs were decomposed into cooperating protocols.[22] This gave rise to the concept of layered protocols which nowadays forms the basis of protocol design.[23] Systems typically do not use a single protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a protocol suite.[24] Some of the best-known protocol suites are TCP/IP, IPX/SPX, X.25, AX.25 and AppleTalk. The protocols can be arranged based on functionality in groups, for instance, there is a group of transport protocols. The functionalities are mapped onto the layers, each layer solving a distinct class of problems relating to, for instance: application-, transport-, internet- and network interface-functions.[25] To transmit a message, a protocol has to be selected from each layer. The selection of the next protocol is accomplished by extending the message with a protocol selector for each layer.[26] Types There are two types of communication protocols, based on their representation of the content being carried: text-based and binary.[27] Text-based A text-based protocol or plain text protocol represents its content in human-readable format, often in plain text. The immediate human readability stands in contrast to binary protocols which have inherent benefits for use in a computer environment (such as ease of mechanical parsing and improved bandwidth utilization). Network applications have various methods of encapsulating data. One method very common with Internet protocols is a text oriented representation that transmits requests and responses as lines of ASCII text, terminated by a newline character (and usually a carriage return character). Examples of protocols that use plain, human-readable text for its commands are FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), and the finger protocol.[28] Text-based protocols are typically optimized for human parsing and interpretation and are therefore suitable whenever human inspection of protocol contents is required, such as during debugging and during early protocol development design phases. To be clear, all digital communication is fundamentally binary. The "Text" based protocols mentioned here use only binary content, which is made "humanly readable" by a text editor (or other such software). Binary A binary protocol utilizes all values of a byte, as opposed to a text-based protocol which only uses values corresponding to human-readable characters in ASCII encoding. Binary protocols are intended to be read by a machine rather than a human being. Binary protocols have the advantage of terseness, which translates into speed of transmission and interpretation.[29] Binary have been used in the normative documents describing modern standards like EbXML, HTTP/2, HTTP/3 and EDOC.[30] An interface in UML[31] may also be considered a binary protocol. Basic requirements Getting the data across a network is only part of the problem for a protocol. The data received has to be evaluated in the context of the progress of the conversation, so a protocol must include rules describing the context. These kinds of rules are said to express the syntax of the communication. Other rules determine whether the data is meaningful for the context in which the exchange takes place. These kinds of rules are said to express the semantics of the communication. Messages are sent and received on communicating systems to establish communication. Protocols should therefore specify rules governing the transmission. In general, much of the following should be addressed:[32] Data formats for data exchange Digital message bitstrings are exchanged. The bitstrings are divided in fields and each field carries information relevant to the protocol. Conceptually the bitstring is divided into two parts called the header and the payload. The actual message is carried in the payload. The header area contains the fields with relevance to the operation of the protocol. Bitstrings longer than the maximum transmission unit (MTU) are divided in pieces of appropriate size.[33] Address formats for data exchange Addresses are used to identify both the sender and the intended receiver(s). The addresses are carried in the header area of the bitstrings, allowing the receivers to determine whether the bitstrings are of interest and should be processed or should be ignored. A connection between a sender and a receiver can be identified using an address pair (sender address, receiver address). Usually, some address values have special meanings. An all-1s address could be taken to mean an addressing of all stations on the network, so sending to this address would result in a broadcast on the local network. The rules describing the meanings of the address value are collectively called an addressing scheme.[34] Address mapping Sometimes protocols need to map addresses of one scheme on addresses of another scheme. For instance, to translate a logical IP address specified by the application to an Ethernet MAC address. This is referred to as address mapping.[35] Routing When systems are not directly connected, intermediary systems along the route to the intended receiver(s) need to forward messages on behalf of the sender. On the Internet, the networks are connected using routers. The interconnection of networks through routers is called internetworking. Detection of transmission errors Error detection is necessary on networks where data corruption is possible. In a common approach, a CRC of the data area is added to the end of packets, making it possible for the receiver to detect differences caused by corruption. The receiver rejects the packets on CRC differences and arranges somehow for retransmission.[36] Acknowledgements Acknowledgement of correct reception of packets is required for connection-oriented communication. Acknowledgments are sent from receivers back to their respective senders.[37] Loss of information - timeouts and retries Packets may be lost on the network or be delayed in transit. To cope with this, under some protocols, a sender may expect an acknowledgment of correct reception from the receiver within a certain amount of time. Thus, on timeouts, the sender may need to retransmit the information.[a] In case of a permanently broken link, the retransmission has no effect, so the number of retransmissions is limited. Exceeding the retry limit is considered an error.[38] Direction of information flow Direction needs to be addressed if transmissions can only occur in one direction at a time as on half-duplex links or from one sender at a time as on a shared medium. This is known as media access control. Arrangements have to be made to accommodate the case of collision or contention where two parties respectively simultaneously transmit or wish to transmit.[39] Sequence control If long bitstrings are divided into pieces and then sent on the network individually, the pieces may get lost or delayed or, on some types of networks, take different routes to their destination. As a result, pieces may arrive out of sequence. Retransmissions can result in duplicate pieces. By marking the pieces with sequence information at the sender, the receiver can determine what was lost or duplicated, ask for necessary retransmissions and reassemble the original message.[40] Flow control Flow control is needed when the sender transmits faster than the receiver or intermediate network equipment can process the transmissions. Flow control can be implemented by messaging from receiver to sender.[41] Queueing Communicating processes or state machines employ queues (or "buffers"), usually FIFO queues, to deal with the messages in the order sent, and may sometimes have multiple queues with different prioritization. Protocol design Systems engineering principles have been applied to create a set of common network protocol design principles. The design of complex protocols often involves decomposition into simpler, cooperating protocols. Such a set of cooperating protocols is sometimes called a protocol family or a protocol suite,[24] within a conceptual framework. Communicating systems operate concurrently. An important aspect of concurrent programming is the synchronization of software for receiving and transmitting messages of communication in proper sequencing. Concurrent programming has traditionally been a topic in operating systems theory texts.[42] Formal verification seems indispensable because concurrent programs are notorious for the hidden and sophisticated bugs they contain.[43] A mathematical approach to the study of concurrency and communication is referred to as communicating sequential processes (CSP).[44] Concurrency can also be modeled using finite state machines, such as Mealy and Moore machines. Mealy and Moore machines are in use as design tools in digital electronics systems encountered in the form of hardware used in telecommunication or electronic devices in general.[45][better source needed] The literature presents numerous analogies between computer communication and programming. In analogy, a transfer mechanism of a protocol is comparable to a central processing unit (CPU). The framework introduces rules that allow the programmer to design cooperating protocols independently of one another. Layering Figure 2. Protocols in relation to the Internet layering scheme. Figure 2. The TCP/IP model or Internet layering scheme and its relation to some common protocols. In modern protocol design, protocols are layered to form a protocol stack. Layering is a design principle that divides the protocol design task into smaller steps, each of which accomplishes a specific part, interacting with the other parts of the protocol only in a small number of well-defined ways. Layering allows the parts of a protocol to be designed and tested without a combinatorial explosion of cases, keeping each design relatively simple. The communication protocols in use on the Internet are designed to function in diverse and complex settings. Internet protocols are designed for simplicity and modularity and fit into a coarse hierarchy of functional layers defined in the Internet Protocol Suite.[46] The first two cooperating protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP) resulted from the decomposition of the original Transmission Control Program, a monolithic communication protocol, into this layered communication suite. The OSI model was developed internationally based on experience with networks that predated the internet as a reference model for general communication with much stricter rules of protocol interaction and rigorous layering. Typically, application software is built upon a robust data transport layer. Underlying this transport layer is a datagram delivery and routing mechanism that is typically connectionless in the Internet. Packet relaying across networks happens over another layer that involves only network link technologies, which are often specific to certain physical layer technologies, such as Ethernet. Layering provides opportunities to exchange technologies when needed, for example, protocols are often stacked in a tunneling arrangement to accommodate the connection of dissimilar networks. For example, IP may be tunneled across an Asynchronous Transfer Mode (ATM) network. Timing is critical. You must add your name to this company's payout list as soon as possible - Because every day you wait could be another missed Dividend check in your pocket. [So click here right now to claim your FREE report,]( and you could be collecting this company's monthly dividend check for the rest of your life! Assembler An assembler program creates object code by translating combinations of mnemonics and syntax for operations and addressing modes into their numerical equivalents. This representation typically includes an operation code ("opcode") as well as other control bits and data. The assembler also calculates constant expressions and resolves symbolic names for memory locations and other entities.[20] The use of symbolic references is a key feature of assemblers, saving tedious calculations and manual address updates after program modifications. Most assemblers also include macro facilities for performing textual substitution â e.g., to generate common short sequences of instructions as inline, instead of called subroutines. Some assemblers may also be able to perform some simple types of instruction set-specific optimizations. One concrete example of this may be the ubiquitous x86 assemblers from various vendors. Called jump-sizing,[20] most of them are able to perform jump-instruction replacements (long jumps replaced by short or relative jumps) in any number of passes, on request. Others may even do simple rearrangement or insertion of instructions, such as some assemblers for RISC architectures that can help optimize a sensible instruction scheduling to exploit the CPU pipeline as efficiently as possible.[21] Assemblers have been available since the 1950s, as the first step above machine language and before high-level programming languages such as Fortran, Algol, COBOL and Lisp. There have also been several classes of translators and semi-automatic code generators with properties similar to both assembly and high-level languages, with Speedcode as perhaps one of the better-known examples. There may be several assemblers with different syntax for a particular CPU or instruction set architecture. For instance, an instruction to add memory data to a register in a x86-family processor might be add eax,[ebx], in original Intel syntax, whereas this would be written addl (%ebx),%eax in the AT&T syntax used by the GNU Assembler. Despite different appearances, different syntactic forms generally generate the same numeric machine code. A single assembler may also have different modes in order to support variations in syntactic forms as well as their exact semantic interpretations (such as FASM-syntax, TASM-syntax, ideal mode, etc., in the special case of x86 assembly programming). Number of passes There are two types of assemblers based on how many passes through the source are needed (how many times the assembler reads the source) to produce the object file. One-pass assemblers process the source code once. For symbols used before they are defined, the assembler will emit "errata" after the eventual definition, telling the linker or the loader to patch the locations where the as yet undefined symbols had been used. Multi-pass assemblers create a table with all symbols and their values in the first passes, then use the table in later passes to generate code. In both cases, the assembler must be able to determine the size of each instruction on the initial passes in order to calculate the addresses of subsequent symbols. This means that if the size of an operation referring to an operand defined later depends on the type or distance of the operand, the assembler will make a pessimistic estimate when first encountering the operation, and if necessary, pad it with one or more "no-operation" instructions in a later pass or the errata. In an assembler with peephole optimization, addresses may be recalculated between passes to allow replacing pessimistic code with code tailored to the exact distance from the target. The original reason for the use of one-pass assemblers was memory size and speed of assembly â often a second pass would require storing the symbol table in memory (to handle forward references), rewinding and rereading the program source on tape, or rereading a deck of cards or punched paper tape. Later computers with much larger memories (especially disc storage), had the space to perform all necessary processing without such re-reading. The advantage of the multi-pass assembler is that the absence of errata makes the linking process (or the program load if the assembler directly produces executable code) faster.[22] Example: in the following code snippet, a one-pass assembler would be able to determine the address of the backward reference BKWD when assembling statement S2, but would not be able to determine the address of the forward reference FWD when assembling the branch statement S1; indeed, FWD may be undefined. A two-pass assembler would determine both addresses in pass 1, so they would be known when generating code in pass 2. S1 B FWD ... FWD EQU * ... BKWD EQU * ... S2 B BKWD High-level assemblers More sophisticated high-level assemblers provide language abstractions such as: High-level procedure/function declarations and invocations Advanced control structures (IF/THEN/ELSE, SWITCH) High-level abstract data types, including structures/records, unions, classes, and sets Sophisticated macro processing (although available on ordinary assemblers since the late 1950s for, e.g., the IBM 700 series and IBM 7000 series, and since the 1960s for IBM System/360 (S/360), amongst other machines) Object-oriented programming features such as classes, objects, abstraction, polymorphism, and inheritance[23] See Language design below for more details. Assembly language A program written in assembly language consists of a series of mnemonic processor instructions and meta-statements (known variously as declarative operations, directives, pseudo-instructions, pseudo-operations and pseudo-ops), comments and data. Assembly language instructions usually consist of an opcode mnemonic followed by an operand, which might be a list of data, arguments or parameters.[24] Some instructions may be "implied," which means the data upon which the instruction operates is implicitly defined by the instruction itselfâsuch an instruction does not take an operand. The resulting statement is translated by an assembler into machine language instructions that can be loaded into memory and executed. For example, the instruction below tells an x86/IA-32 processor to move an immediate 8-bit value into a register. The binary code for this instruction is 10110 followed by a 3-bit identifier for which register to use. The identifier for the AL register is 000, so the following machine code loads the AL register with the data 01100001.[24] 10110000 01100001 This binary computer code can be made more human-readable by expressing it in hexadecimal as follows. B0 61 Here, B0 means 'Move a copy of the following value into AL, and 61 is a hexadecimal representation of the value 01100001, which is 97 in decimal. Assembly language for the 8086 family provides the mnemonic MOV (an abbreviation of move) for instructions such as this, so the machine code above can be written as follows in assembly language, complete with an explanatory comment if required, after the semicolon. This is much easier to read and to remember. MOV AL, 61h ; Load AL with 97 decimal (61 hex) In some assembly languages (including this one) the same mnemonic, such as MOV, may be used for a family of related instructions for loading, copying and moving data, whether these are immediate values, values in registers, or memory locations pointed to by values in registers or by immediate (a.k.a. direct) addresses. Other assemblers may use separate opcode mnemonics such as L for "move memory to register", ST for "move register to memory", LR for "move register to register", MVI for "move immediate operand to memory", etc. If the same mnemonic is used for different instructions, that means that the mnemonic corresponds to several different binary instruction codes, excluding data (e.g. the 61h in this example), depending on the operands that follow the mnemonic. For example, for the x86/IA-32 CPUs, the Intel assembly language syntax MOV AL, AH represents an instruction that moves the contents of register AH into register AL. The[nb 4] hexadecimal form of this instruction is: 88 E0 The first byte, 88h, identifies a move between a byte-sized register and either another register or memory, and the second byte, E0h, is encoded (with three bit-fields) to specify that both operands are registers, the source is AH, and the destination is AL. In a case like this where the same mnemonic can represent more than one binary instruction, the assembler determines which instruction to generate by examining the operands. In the first example, the operand 61h is a valid hexadecimal numeric constant and is not a valid register name, so only the B0 instruction can be applicable. In the second example, the operand AH is a valid register name and not a valid numeric constant (hexadecimal, decimal, octal, or binary), so only the 88 instruction can be applicable. Assembly languages are always designed so that this sort of unambiguousness is universally enforced by their syntax. For example, in the Intel x86 assembly language, a hexadecimal constant must start with a numeral digit, so that the hexadecimal number 'A' (equal to decimal ten) would be written as 0Ah or 0AH, not AH, specifically so that it cannot appear to be the name of register AH. (The same rule also prevents ambiguity with the names of registers BH, CH, and DH, as well as with any user-defined symbol that ends with the letter H and otherwise contains only characters that are hexadecimal digits, such as the word "BEACH".) Returning to the original example, while the x86 opcode 10110000 (B0) copies an 8-bit value into the AL register, 10110001 (B1) moves it into CL and 10110010 (B2) does so into DL. Assembly language examples for these follow.[24] MOV AL, 1h ; Load AL with immediate value 1 MOV CL, 2h ; Load CL with immediate value 2 MOV DL, 3h ; Load DL with immediate value 3 The syntax of MOV can also be more complex as the following examples show.[25] MOV EAX, [EBX] ; Move the 4 bytes in memory at the address contained in EBX into EAX MOV [ESI+EAX], CL ; Move the contents of CL into the byte at address ESI+EAX MOV DS, DX ; Move the contents of DX into segment register DS In each case, the MOV mnemonic is translated directly into one of the opcodes 88-8C, 8E, A0-A3, B0-BF, C6 or C7 by an assembler, and the programmer normally does not have to know or remember which.[24] Transforming assembly language into machine code is the job of an assembler, and the reverse can at least partially be achieved by a disassembler. Unlike high-level languages, there is a one-to-one correspondence between many simple assembly statements and machine language instructions. However, in some cases, an assembler may provide pseudoinstructions (essentially macros) which expand into several machine language instructions to provide commonly needed functionality. For example, for a machine that lacks a "branch if greater or equal" instruction, an assembler may provide a pseudoinstruction that expands to the machine's "set if less than" and "branch if zero (on the result of the set instruction)". Most full-featured assemblers also provide a rich macro language (discussed below) which is used by vendors and programmers to generate more complex code and data sequences. Since the information about pseudoinstructions and macros defined in the assembler environment is not present in the object program, a disassembler cannot reconstruct the macro and pseudoinstruction invocations but can only disassemble the actual machine instructions that the assembler generated from those abstract assembly-language entities. Likewise, since comments in the assembly language source file are ignored by the assembler and have no effect on the object code it generates, a disassembler is always completely unable to recover source comments. Each computer architecture has its own machine language. Computers differ in the number and type of operations they support, in the different sizes and numbers of registers, and in the representations of data in storage. While most general-purpose computers are able to carry out essentially the same functionality, the ways they do so differ; the corresponding assembly languages reflect these differences. Multiple sets of mnemonics or assembly-language syntax may exist for a single instruction set, typically instantiated in different assembler programs. In these cases, the most popular one is usually that supplied by the CPU manufacturer and used in its documentation. Two examples of CPUs that have two different sets of mnemonics are the Intel 8080 family and the Intel 8086/8088. Because Intel claimed copyright on its assembly language mnemonics (on each page of their documentation published in the 1970s and early 1980s, at least), some companies that independently produced CPUs compatible with Intel instruction sets invented their own mnemonics. The Zilog Z80 CPU, an enhancement of the Intel 8080A, supports all the 8080A instructions plus many more; Zilog invented an entirely new assembly language, not only for the new instructions but also for all of the 8080A instructions. For example, where Intel uses the mnemonics MOV, MVI, LDA, STA, LXI, LDAX, STAX, LHLD, and SHLD for various data transfer instructions, the Z80 assembly language uses the mnemonic LD for all of them. A similar case is the NEC V20 and V30 CPUs, enhanced copies of the Intel 8086 and 8088, respectively. Like Zilog with the Z80, NEC invented new mnemonics for all of the 8086 and 8088 instructions, to avoid accusations of infringement of Intel's copyright. (It is questionable whether such copyrights can be valid, and later CPU companies such as AMD[nb 5] and Cyrix republished Intel's x86/IA-32 instruction mnemonics exactly with neither permission nor legal penalty.) It is doubtful whether in practice many people who programmed the V20 and V30 actually wrote in NEC's assembly language rather than Intel's; since any two assembly languages for the same instruction set architecture are isomorphic (somewhat like English and Pig Latin), there is no requirement to use a manufacturer's own published assembly language with that manufacturer's products. Sincerely, [Tim Plaehn] Tim Plaehn
Former U.S. Air Force Captain
Lead Income Analyst
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