ASP file extension is commonly associated with web based applications provided on a Microsoft IIS. It stands for Active Server Pages. Dynamic website under Windows platform uses this type of extension. This format is commonly used for websites running business-to-business solutions.
ASP is a server-side scripting language bundled with Microsoft's IIS. It can be used to connect to different databases such as MSSQL and MySQL as the backend technology. Files with this extension are mostly written with similar commands as of VBScript. These commands are embedded on a plain HTML page, but saved with an ASP extension. ASP scripts starts with <% and end with %> to distinguish it from the rest of the HTML code.
First release of this extension was with IIS 3.0 under ASP 1.0 in December 1996. With some limitations with applications developed under this extension, Microsoft decided to create ASP.Net with file extension ASPX, a more robust file type.
Since this includes Active Scripting it can be use for malicious intent. Objects of this extension can be coded to search for files on a host computer posing a threat as a spyware.
Web browsers including Internet Explorer, Firefox, Safari and others are able to open this extension through request done from the servers. Other applications such as DreamWeaver and Frontpage can open this extension, but cannot execute embedded commands without installed servers.
Since ASP file is a text file you can open any ASP file using text editor. But it will be more efficient to edit ASP files using specialized software development tools like Visual Studio.
For more general information about files, file extensions and registry you can read one of the following articles:
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