No, there's a Big difference. COM has a well defined protocols for creating objects, exposing methods, managing memory, publishing type information, managing threading. There is practically no language left that doesn't support using a COM server, no matter what language it was written in.
Difference Between Regular Dll And Com Dll
As to where COM differs from 'C', the main difference is the concept of contracts. COM encourages programmers to think in terms of abstract interfaces between modules rather than a hierarchical, top-down decomposition of functionality. This is one kind of 'OOP', but that term is too loose to be of much use, IMO. Advantages of the contract-oriented approach are manifold for strongly-typed, statically linked languages like C/C++.
COM introduced the concept of interfaces, which are immutable so should not be altered between builds, etc. Every COM object must implement the IUnknown interface which contains the QueryInterface method which is used to ask the object for pointers to other supported interfaces.
When a function within a DLL needs an update or a fix, the deployment and installation of the DLL does not require the program to be relinked with the DLL. Additionally, if multiple programs use the same DLL, the multiple programs will all benefit from the update or the fix. This issue may more frequently occur when you use a third-party DLL that is regularly updated or fixed.
When you create an assembly, all the information that is required for the CLR to run the assembly is contained in the assembly manifest. The assembly manifest contains a list of the dependent assemblies. Therefore, the CLR can maintain a consistent set of assemblies that are used in the application. In Win32 DLLs, you cannot maintain consistency between a set of DLLs that are used in an application when you use shared DLLs.
Although DLLs are the core of the Windows architecture, they have several drawbacks, collectively called "DLL hell".[2]As of 2015[update] Microsoft promotes .NET Framework as one solution to the problems of DLL hell, although they now promote virtualization-based solutions such as Microsoft Virtual PC and Microsoft Application Virtualization, because they offer superior isolation between applications. An alternative mitigating solution to DLL hell has been to implement side-by-side assembly.
You can choose between creating an EXE or a DLL when writing Dot NET code. Both of these include executable code, however, DLL and EXE operate differently from one another. The EXE will create its own thread and reserve resources for it if you run it. A DLL file, on the other hand, is an in-process server, so you cannot run a DLL file on its own. A DLL's code is used by a running application by loading and calling the DLL.
Static links. These are linked earlier in the process and are embedded into the executable. Static libraries are linked to the executable when the program is compiled. Dynamic libraries are linked later, either at runtime or at load time. Static libraries are not shared between programs because they are written into the individual executable.
Listen as Robert Stechuk, an expert in the area of young dual language learners, discusses the use of the term for young children. Next, he describes the distinction between simultaneous and sequential learners, followed by some of the key differences between DLLs and children learning only one language.
The downside of this technique is that the malicious DLL file must be stored on disk, which exposes it to detection by regular security solutions. Nevertheless, this technique is employed by malware developers and is widespread in the wild. For example, Poison Ivy, a popular and long-standing RAT, uses DLL injection. Poison Ivy has been involved in several APT campaigns recommending itself as a tool of choice by APT groups for espionage operations.
Modern systems use synchronous communication to achieve high data transmission rates to and from the DRAMs in the memory system. Systems that communicate synchronously use a clock signal as a timing reference so that data can be transmitted and received with a known relationship to this reference. A difficulty in maintaining this relationship is that process, voltage, and temperature variations can alter the timing relationship between the clock and data signals, resulting in reduced timing margins. This problem gets worse as signaling speeds increase, limiting the ability of systems to communicate data at higher speeds.
Delay Lock Loops (DLLs) and Phase Lock Loops (PLLs) serve similar purposes, and can be used to maintain a fixed timing relationship between signals in environments where process, voltage, and temperature variations cause these relationships to change over time. DLLs and PLLs work by continuously comparing the relationship between two signals and providing feedback to adjust and maintain a fixed relationship between them. Rambus DRAMs were the first DRAMs to incorporate DLLs and PLLs, an important innovation that resulted in increased signaling speeds, compared to alternative DRAM technologies.
A DLL is used to maintain the timing relationship between a clock signal and an output data signal. A critical element of the DLL is the phase detector, which detects phase differences between the clock and output data. The phase detector detects this phase difference, and sends control information through a low pass filter to a variable delay line that adjusts the timing of the internal clock to maintain the desired timing relationship (PLLs use a voltage controlled oscillator to adjust this timing relationship). One of the difficulties of maintaining phase relationships between these two signals is that the loop which provides feedback to the phase detector must account for the timing characteristics of the output logic and output driver. This is important, as it estimates the phase differences between the clock and the data being driven by the output driver. In order to accomplish this, circuits that mimic the behavioral characteristics of the output logic and output driver are inserted into this feedback loop to model timing delays and changes in behavior as process, voltage, and temperature vary. Maintaining the timing relationships between the clock and output data in this manner with DLLs and PLLs results in improved timing margins (as shown in Figure 4), and addresses an important limitation to increasing signaling speeds.
End Users, DRAM manufacturers, designers and integrators can all benefit by incorporating a DLL/PLL on a DRAM. By providing a fixed timing relationship between clock and data signals, DRAM performance is allowed to increase and end users are able to benefit from the overall improvement in system performance. DRAM manufactures are able to reduce production costs and improve DRAM yields with the ability to adjust the timing relationships to compensate for variations in process, voltage and temperature, improving timing margins. By enabling high per-pin transfer rates, DLLs and PLLs allow controller and board designers to reduce IO pin counts, which decreases packaging costs, component count, routing area, and routing complexity. Finally, the ability of DLLs and PLLs to provide fixed timing relationships lets component manufacturers and system integrators relax the specifications. In systems with varying temperature and voltage characteristics, system thermal and power delivery requirements can be relaxed and the DRAMs can still maintain good timing margins, while lowering the costs of the thermal solution, power supply, and system manufacturing.
Distal-less DEVELOPMENTAL BIOLOGY Effects of Mutation or Deletion Since Dll mutations are lethal, it is impossible to observe the effects on adult animals. Larvae however, have rudimentary limbs. In the absence of Dll, these vestigial limbs are deleted. Keilin organs, a distal sensory apparatus of larval appendages, are associated with the developing leg imaginal disc primordia. Thus these sense organs are the rudimentary legs of Drosophila embryos. In Dll mutants, the sensory hairs of Keilin's organs are deleted (S.M. Cohen, 1989).Dll protein can be detected in a central domain in legdiscs throughout most of larval development; in mature discs this domain corresponds to the distal-most regions of the leg: the tarsus and the distal tibia. Clonal analysis reveals that late in development these are the only regions in which Dll function isrequired. Dll3 is the strongest hypomorph in which all of the tarsus is deleted and the tibia and femur are reduced in size. Theexpression of two genes required for the patterning of the tarsus,al and bric à brac (bab) was examined in Dll3leg discs. In wild-type discs, al is expressed in the center of thedisc and bab in the rest of the presumptive tarsus. In Dll3 leg discs no al or babexpression can be detected in the center of the discs.Clonal analysis was performed with a Dll null allele. Clones were generated at various times during development and theresulting adult legs were compared to legs containing wild-typeclones generated at the same time. Dll clones generated early indevelopment fail to be recovered in the region more distalthan the coxa, while later in development phenotypically wild-typeDll clones (but lacking bracts) could be recovered in theproximal tibia and femur but not in more distal regions, wherethey segregate out as cuticular vesicles. The requirement for Dll in thefemur and most of the tibia is lost by about the early thirdinstar. Additional observations reveal that there is a clear difference in thetime at which normally patterned Dll null clones can berecovered in the dorsal femur, as compared to the ventral femur (here'ventral' corresponds only to the ventral third): Dll null clonescan be recovered in the dorsal femur when they are generatedat any stage in development, although earlyin development their frequency is reduced when compared to wild-type.In the trochanter, almost no wild-type Dll clones arerecovered at any stage in development; there is aproximal ring of Dll expression in the third instar leg disc thatprobably corresponds to the trochanter.When a leg is composed almost entirely of Dll null mutanttissue then the region more distalto the coxa is represented only by a small stump of tissue. A marked reduction in the P/D axis can be identified inleg discs consisting almost entirely of Dll null tissue,showing that the leg truncations produced by loss of Dll arenot caused simply by cell death late in development but maybe caused by disruption of normal patterning and growth orcell survival during development. In discs containing largerregions of wild-type tissue, this tissue is generally found in thecenter of the disc surrounded by Dll null tissue, in contrast to wild-type clones that form irregular patternscontributing to any region of the leg. Legs derived from thesetypes of discs develop normal distal regions, but the leg betweenthis region and the coxa is aberrant: there is a marked reductionin growth, the division into segments is disrupted and the sizeand density of bristles is reduced (Campbell, 1998). Proximodistal axis formation in the Drosophila leg: subdivision into proximal and distal domains by Homothorax and Distal-lessThe developing legs of Drosophila are subdivided intoproximal and distal domains by the activity of thehomeodomain proteins Homothorax (Hth) and Distal-less(Dll). The expression domains of Dll and Hth are initiallyreciprocal. In the mature third instar disc, Dll isexpressed in a large central domain that corresponds to thepresumptive tarsus and distal tibia. Dll is also expressedin a secondary ring. X-gal staining of adultlegs carrying a Dll-lacZ reporter gene shows that this ring islocated at the proximal edge of the femur, possibly extendingslightly into the distal trochanter. The central domain of Dll expression is controlled by Wg and Dpp. The proximal ring arises in third instar and does not depend on Wgor Dpp activity. The leg disc is a continuous single-layered epithelial sheetthat forms a series of folds as it grows. The peripheral regionof the disc forms the proximal segments. This region is foldedback over the central region where Dll is expressed. The domain of Hthexpression extends from the peripodial membrane at thetop, through the coxa and trochanter segmentprimordia. The distal-most portion of the Hth domain overlapsthe proximal part of the dac-lacZ domain within theproximal ring of Dll expression in the femur.Dll is expressed alone in the central folds of the disc (whichcorrespond to tarsal segment primordia). In proximal tarsusand tibia, Dll and Dac overlap. Dac is expressedalone in the presumptive femur. Becausethe disc is highly folded, horizontal optical sections makeproximal and distal regions of the disc appear to be closelyapposed, although they are actually far apart along the PD axisin the plane of the disc epithelium. Hth is expressed in the upper layerand around the lateral sides of the epithelial sac. Dll isexpressed in the center of the lower layer. The twoexpression domains abut, but do not overlap. dac-lacZis not detectably expressed at this stage, but can bereliably detected in slightly older discs at the transition from second to third instar. These observations suggest that the primary subdivision of the disc is into two domains: a central Dll-expressing domain and a proximal Hth-expressing domain. Wg and Dpp act together to induce Dll and Dac in the center of the leg disc. Wg and Dpp repress Hth and Teashirt, but not through activation of Dll (Wu, 1999).The expression patterns of Dll and Hth/Exd reflect an earlysubdivision of the disc into proximal and distal domains. Atearly stages of disc development, Dll and Hth/Exd areexpressed in reciprocal domains that account for all cells ofthe disc. At thisstage, Dac is not yet expressed. What is the relationship between Dll and Hth/Exd expression in the early disc? The Dlldomain is defined by Wg and Dpp signaling. The same signals repress nuclear localization ofExd and Hth expression. The reciprocity of Dll and Hthexpression suggests a model in which Wg and Dpp act throughDll to repress Hth in the early disc. However, the analysis ofmarked Dll mutant clones reported here shows that this is not the case.Clones of Dll mutant cells located in the distal region of theleg do not express Hth. This contrasts with recentreports by GonzÃlez-Crespo (1998) and Abu-Shaar (1998) in which evidence is presented for ectopicexpression of Exd and Hth in Dll mutant clones.How can the difference in the results betweenthese reports be reconciled? In both studies, the clones were induced in secondinstar larvae using the same allele of Dll. In the experiments reported here,clones were marked by the absence of Dll protein and by theabsence of a neutral beta-gal marker, which permits definitivegenotyping of the cells independent of Dll expression. In theother reports, clones were marked only by the absence of Dll.The disc epithelium is highly folded and the proximal Hth-expressingepithelium is very close to the distal Dll-expressingepithelium. Unless cells in the clone aredefinitively genotyped, it is difficult to distinguish a genuineclone from a patch of the overlying Hth-expressing proximalepithelium that has been pushed downward into the plane of theoptical section. Serial optical sections of wild-type discs showthat this type of distortion of the disc epithelium can occur indamaged discs as well as in discs that are not obviouslydamaged. How is Hth repressed by Wg and Dpp? Dac is induced byWg and Dpp toward the end of second instar. Hth expands distally, to some extent, in Dacmutant discs. These observations suggest that Dac contributes to Hthrepression. However, Hth is repressedprior to the onset of Dac expression indicating thatDac cannot be the primary repressor. Whether Wg and Dpp actdirectly to repress Hth expression or act via another as yetunidentified repressor remains to be determined (Wu, 1999).In conclusion, Hth and Dll expression appear to definealternative fates in the second instar disc. Under normalcircumstances, there does not appear to be a cell lineagerestriction between these populations (i.e. no compartmentboundary). These results suggest that cells can cross betweenthese territories if they are able to switch between Hth and Dllexpression. This situation appears to be analogous to the DVsubdivision of the leg disc (as opposed to the proximal distal subdivision reported here). DV subdivision is stable at the levelof gene expression in a cell population, but is not a clonallineage restriction boundary. Similarly, the separation of proximal and distal cellpopulations requires Hth function. These results suggest thatcells at the interface between these two territories arespecialized to allow integration of otherwise immisciblepopulations of cells (Wu, 1999 and references).Drosophila terminalia as an appendage-like structureThis study reports the expression pattern of Dll in the genital disc, the requirement of Dll activity for the development of the terminalia and the activation of Dll by the combined action of the morphogenetic signals Wingless (Wg) and Decapentaplegic (Dpp). In Drosophila, the terminalia comprise the entire set of internal and external genitalia (with the exception of thegonads), and includes the hindgut and the anal structures. They arise from a single imaginal disc of ventral origin that has a complex organization and shows bilateral symmetry. The genital disc shows extreme sexual dimorphism. Early in development,the anlage of the genital disc of both sexes consists of threeprimordia: the female genital primordium (FGP); the malegenital primordium (MGP), and the anal primordium (AP).In both sexes, only two of the three primordia develop: thecorresponding genital primordium and the anal primordium.These in turn develop, according to the genetic sex, intofemale or male analia. The undeveloped genital primordiumis the repressed primordium (either RFP or RMP,for the respective female and male genital primordia) (Gorfinkiel, 1999).During the development of the two components of the anal primordium -- the hindgut and the analia -- only the latter is dependent on Dll and hedgehog (hh) function. The hindgut is defined by the expression of the homeobox gene even-skipped. The lack of Dll function in the anal primordia transforms the anal tissue into hindgut by the extension of the eve domain. Meanwhile targeted ectopic Dll represses eve expression and hindgut formation. The Dll requirement for the development of both anal plates in males and only for the dorsal anal plate in females, provides further evidence for the previously held idea that the analia arise from two primordia. In addition, evaluation was made of the requirement for the optomotor-blind (omb) gene which, as in the leg and antenna, is located downstream of Dpp. These results suggest that the terminalia show similar behavior as the leg disc or the antennal part of the eye-antennal disc, consistent with both the proposed ventral origin of the genital disc and the evolutive consideration of the terminalia as an ancestral appendage (Gorfinkiel, 1999). The expression pattern of Dll in the genital disc wasanalyzed. Dll is neither expressed in the embryonic terminalia nor in the embryonic precursor cells ofthe genital disc. In the female third larvalinstar genital disc, Dll shows a localized distribution; itis strongly expressed in a large spot in the central partof the anal primordium and in a faint band of cells in thegenital primordium. It is not detected in the RMP. Similarly, in the male genital disc, Dll is expressed in a largespot both in the anal primordium and in the male genitalprimordium but not in the RFP.Several GAL4 insertions in the Dlllocus were used and these permitted the identifcation of theadult regions where Dll is expressed according to theobserved X-Gal staining. I