Virtual Hard Disk. A disk image for Microsoft Virtual Server. Microsoft has set the Virtual Hard Disk (VHD) file format as the standard for running and managing virtual machines using Microsoft Virtual Server 2005. The VHD file format provides for a range of disk types, including dynamically expanding, linked, undo, and differencing disks.
Source file written in VHDL, which stands for Very High Speed Integrated Circuits (VHSIC) Hardware Description Language (HDL); often used for automating the design of electrical circuits and components. Electronic engineers can use VHDL to describe hardware components in a text-based format; this description can then be used to manufacture a physical circuit such as a motherboard, processor, or memory module.