The file with .res suffix or extension can belong to many file format categories. Here we are discussing the RES file format which is a C++ Compiled Resource Script; a binary file created by the Microsoft Resource Compiler (rc) that contains resource data; based on the resource-definition file’s contents; relevant to its parent software project. The .res file usually re-formatted into a resource object file to link it to the executable file of an application.
RES file format
The RES file format belongs to the Microsoft Resource Compiler (rc). The resource compiler is a tool that compiles resources such as cursors, icons, menus, and dialog boxes, that your application uses. The resource files usually have a .res extension; contains resources, such as cursors, images, and version information. An RES file could be a 16 or 32-bit resource file.
Resource file structure
A resource file contains a series of various resource entries. Each entry contains a resource header and relevant data. A resource header is usually DWORD-aligned in the file and contains the following:
A DWORD to specify the size of the resource header
A DWORD to specify the size of the resource data
The resource type
The resource name
Additional resource information
The resource header structure defines the format of the RES file. The data for the resource follows the resource header. Some resources also add a resource-specific group header pattern to provide information about a group of resources. Following are some of the resource entry types and their description:
Accelerator Table Resources
An accelerator table is a resource entry in a RES file without a group header. The ACCELTABLEENTRY pattern defines each entry in the accelerator table. A RES file may have Multiple accelerator tables.
Cursor and Icon Resources
Although, the system considers each icon and cursor as a single file, but these are stored in RES files as a group of icon resources or a group of cursor resources. The file formats of icon and cursor resources are same. A resource group header follows all of the individual icon or cursor group components in the .res file.
Dialog Box Resources
A dialog box is also realized as a resource entry in the RES file. It contains one DLGTEMPLATE dialog box header pattern and one DLGITEMTEMPLATE pattern for each specific control in the dialog box. The DLGTEMPLATEEX and the DLGITEMTEMPLATEEX patterns explain the format of extended dialog box resources.
A menu resource contains a MENUHEADER pattern subsequently one or more NORMALMENUITEM or POPUPMENUITEM patterns, one for each menu item in the menu template. The MENUEX_TEMPLATE_HEADER and the MENUEX_TEMPLATE_ITEM patterns explains the format of extended menu resources.
Message Table Resources
A message table consists of formatted text for display as an error message or in a message box. The main pattern in a message table resource is the MESSAGE_RESOURCE_DATA structure.
The main pattern in a version resource is the VS_FIXEDFILEINFO. Additional patterns include the VarFileInfo to store language information related data, and StringFileInfo for custom string information.