executable code itself functions in the library DLL, which contains several compiled, linked and stored functions in the process used.DLL is used to simplify the process of sharing and data sources.It allows your programs to have simultaneous access to multiple content of one loaded in the memory copy of the DLL.

modular coding - the ancestor library DLL

the beginning of work on the creation of a DLL can be regarded as the emergence of such a programming method as modular coding.Modular coding at one time greatly facilitate the work of programmers, allowing not to write the same code for each new program several times.All simple programs contain many similar code that began to make out in the form of modules by adding them to ne
w applications.For some time the modular coding was the most simple and effective solution and has only one drawback.Identical modules are added to the program of disk space, which in those days were few.

problem waste disk space on the same module was the only one until there were only single-tasking operating system.With the advent of multi-tasking operating systems, such as for example Windows, there is another problem.Now, with the program modules with the same code at the same time began to run the ship in his memory, "eating" all the resources.It is worth noting that at that time the memory module 500 megabytes was the largest of the existing, and it cost quite expensive.But even the maximum amount of RAM is not saved user program loads the RAM completely, making it impossible to the normal operation of the computer.

emergence of library DLL

decent solution to these problems has been found, it looked like this: module with the same code no longer docked with the main program, keeping them in a separate executable file, which could be as necessary to handle any application.That decision is the basis of libraries in DLL, which is dynamically connected to any programs.Now you can be stored in these libraries, the executable code in a function or procedure, graphics and even videos that will save disk space and memory resources.

only drawback of dynamic libraries - spend the extra time to download the program.Besides the lack of non-essential DLL it consists of nothing but advantages.Therefore, these libraries are widely used and programmers used in almost every application.