Windows 1.0 was the only one that allowed limited multi-tasking of MS-DOS applications, focusing rather on the creation of user interaction standards, a model for application launch and a stable native application programming interface (API) for later use. Thanks to Microsoft's strong support for backward compatibility, it is not only possible to run Windows 1.0 programs on newer versions of the system without any problems, but even to recompile their source code and thus create relatively modern applications after minor rework. Windows 1.0 was often considered to be a "front-end" for MS-DOS - a term that also applied to later versions. Indeed, the environment itself was run from the DOS command line, programs written for Windows could invoke MS-DOS functions, and were themselves, as in DOS, contained in files with the .exe extension. However, the .exe files used in Windows had their own format - the "new executable" (New Executable, NE) - which could only be processed in Windows environment and which allowed, among other things, to load portions of code and data on demand. Applications were supposed to refer to the memory only through the Windows memory management system, which created a software model of virtual memory, which allowed to run applications exceeding the size of the operating memory available in the computer.
The first independent version of Microsoft Windows with version number 1.0 was released in 1985. However, it was not equipped with a wide range of features, so it was not adopted on the market. Originally the name for the overlay was to be Interface Manager, but Rowland Hanson, head of marketing at Microsoft, convinced the rest of the team that the Windows name would be better adopted. Windows 1.0 was not a complete operating system, but only an extension of MS-DOS and as such inherited all of its imperfections and problems. Additionally, the programs delivered with the early versions of Windows were rather "toys" that did not meet the expectations of corporate customers. The position of the first Windows was not strengthened by the transfer of the little-known, but then strong CorelDRAW! Windows 1.0 on a larger scale never saw the light of day. The version, which is usually called Windows 1.0 is Windows 1.01. Windows 1.00 had problems with CGA graphics cards - with a faster processor clock, the color palette switching technique synchronized the display making it impossible to work.
Another reason for limitations of the overlay's functionality were copyright issues, which were held by Apple. For example, in Microsoft's products, individual windows could only be arranged adjacent to each other and could not overlap each other. The first version of Windows also did not have a trashcan - a place where you could store files before they were finally deleted. Apple claimed to have copyrights to these solutions. Microsoft only removed both restrictions after signing a license agreement with Apple.