what are dll’s?

Mar 4, 2009

DLL Libraries


Dynamic Link Libraries (DLL) are an important structural component of Microsoft Windows. DLLs allow certain code fragments to be compiled into a single library, and to be linked to by multiple programs. This means that only one copy of the library needs to exist, and multiple programs can share the functions and the data between them. The difference between a DLL and a static library is that when you compile your programs, the DLL is not compiled into your executable, but instead remains a separate module. This feature helps to keep executable size low, and also allows for a DLL to be loaded into memory only when it is needed.

Advantages of DLL files
If you check the system files and program files folder you will find a lot of files with DLL extension, In this post lets learn about dll files and their advantages, i hope you will find it useful and interesting.

Third-party applications aside from the Windows platform can also employ dynamic-link library (DLL) files to take advantage of the benefits provided by DLLs, particularly in saving RAM and hard disk space. DLLs do not need multiple copies to be present in the system since applications can simultaneously use the functions and protocols embedded on a single DLL. This is why it saves hard disk space and valuable memory resources.

The software developer may use a third-party software module that can be reused to enhance the quality and efficiency of programming custom applications. Once again, developers of these third-party components employ DLLs to enjoy the advantages offered by shared libraries. One of these benefits is modularity, which makes it easy for the programmer to make modifications to code that is often used in a single DLL file applied several times by a program and by various application features.
The utilization of standard interfaces for plug-ins is another advantage obtained by third-party software developers from the employment of DLL files. Only a lone interface may be required to integrate older modules with newer ones on existing applications during run-time without having to alter the application itself.
The programmer connects the code to an import library through an Import Address Table (IAT) when third-party executable files are developed. During run-time, the program fills its IAT with the proper addresses connecting to a function in a DLL file only loaded into memory when it is called.

Similar to DLL files needed by Windows, DLLs employed by third-party applications also contain data, executable code, or resources in any combination. The EXE contains the list of instructions to be performed by a DLL module, while the data and resources provide the appropriate information. DLL files for the 32- and 64-bit operating systems are in the Portable Executable (PE) format, while those for the 16-bit OS are in the New Executable (NE) format.

The NE format is a segmented executable file. The PE format superseded the NE format and has the advantage of not being affected by the type of architecture used.

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