IMAGE_OPTIONAL_HEADER Structure

Represents the optional header format.

typedef struct _IMAGE_OPTIONAL_HEADER {
  WORD Magic;
  BYTE MajorLinkerVersion;
  BYTE MinorLinkerVersion;
  DWORD SizeOfCode;
  DWORD SizeOfInitializedData;
  DWORD SizeOfUninitializedData;
  DWORD AddressOfEntryPoint;
  DWORD BaseOfCode;
  DWORD BaseOfData;
  DWORD ImageBase;
  DWORD SectionAlignment;
  DWORD FileAlignment;
  WORD MajorOperatingSystemVersion;
  WORD MinorOperatingSystemVersion;
  WORD MajorImageVersion;
  WORD MinorImageVersion;
  WORD MajorSubsystemVersion;
  WORD MinorSubsystemVersion;
  DWORD Win32VersionValue;
  DWORD SizeOfImage;
  DWORD SizeOfHeaders;
  DWORD CheckSum;
  WORD Subsystem;
  WORD DllCharacteristics;
  DWORD SizeOfStackReserve;
  DWORD SizeOfStackCommit;
  DWORD SizeOfHeapReserve;
  DWORD SizeOfHeapCommit;
  DWORD LoaderFlags;
  DWORD NumberOfRvaAndSizes;
  IMAGE_DATA_DIRECTORY DataDirectory[IMAGE_NUMBEROF_DIRECTORY_ENTRIES];
} IMAGE_OPTIONAL_HEADER, 
 *PIMAGE_OPTIONAL_HEADER;

Members

Magic

The state of the image file. This member can be one of the following values.

Value	Meaning
IMAGE_NT_OPTIONAL_HDR_MAGIC	The file is an executable image. This value is defined as IMAGE_NT_OPTIONAL_HDR32_MAGIC in a 32-bit application and as IMAGE_NT_OPTIONAL_HDR64_MAGIC in a 64-bit application.
IMAGE_NT_OPTIONAL_HDR32_MAGIC 0x10b	The file is an executable image.
IMAGE_NT_OPTIONAL_HDR64_MAGIC 0x20b	The file is an executable image.
IMAGE_ROM_OPTIONAL_HDR_MAGIC 0x107	The file is a ROM image.

MajorLinkerVersion

The major version number of the linker.

MinorLinkerVersion

The minor version number of the linker.

SizeOfCode

The size of the code section, in bytes, or the sum of all such sections if there are multiple code sections.

SizeOfInitializedData

The size of the initialized data section, in bytes, or the sum of all such sections if there are multiple initialized data sections.

SizeOfUninitializedData

The size of the uninitialized data section, in bytes, or the sum of all such sections if there are multiple uninitialized data sections.

AddressOfEntryPoint

A pointer to the entry point function, relative to the image base address. For executable files, this is the starting address. For device drivers, this is the address of the initialization function. The entry point function is optional for DLLs. When no entry point is present, this member is zero.

BaseOfCode

A pointer to the beginning of the code section, relative to the image base.

BaseOfData

A pointer to the beginning of the data section, relative to the image base.

ImageBase

The preferred address of the first byte of the image when it is loaded in memory. This value is a multiple of 64K bytes. The default value for DLLs is 0x10000000. The default value for applications is 0x00400000, except on Windows CE where it is 0x00010000.

SectionAlignment

The alignment of sections loaded in memory, in bytes. This value must be greater than or equal to the FileAlignment member. The default value is the page size for the system.

FileAlignment

The alignment of the raw data of sections in the image file, in bytes. The value should be a power of 2 between 512 and 64K (inclusive). The default is 512. If the SectionAlignment member is less than the system page size, this member must be the same as SectionAlignment.

MajorOperatingSystemVersion

The major version number of the required operating system.

MinorOperatingSystemVersion

The minor version number of the required operating system.

MajorImageVersion

The major version number of the image.

MinorImageVersion

The minor version number of the image.

MajorSubsystemVersion

The major version number of the subsystem.

MinorSubsystemVersion

The minor version number of the subsystem.

Win32VersionValue

This member is reserved and must be 0.

SizeOfImage

The size of the image, in bytes, including all headers. Must be a multiple of SectionAlignment.

SizeOfHeaders

The combined size of the MS-DOS stub, the PE header, and the section headers, rounded to a multiple of the value specified in the FileAlignment member.

CheckSum

The image file checksum. The following files are validated at load time: all drivers, any DLL loaded at boot time, and any DLL loaded into a critical system process.

Subsystem

The subsystem required to run this image. The following values are defined.

Value	Meaning
IMAGE_SUBSYSTEM_UNKNOWN 0	Unknown subsystem.
IMAGE_SUBSYSTEM_NATIVE 1	No subsystem required (device drivers and native system processes).
IMAGE_SUBSYSTEM_WINDOWS_GUI 2	Windows graphical user interface (GUI) subsystem.
IMAGE_SUBSYSTEM_WINDOWS_CUI 3	Windows character-mode user interface (CUI) subsystem.
IMAGE_SUBSYSTEM_OS2_CUI 5	OS/2 CUI subsystem.
IMAGE_SUBSYSTEM_POSIX_CUI 7	POSIX CUI subsystem.
IMAGE_SUBSYSTEM_WINDOWS_CE_GUI 9	Windows CE system.
IMAGE_SUBSYSTEM_EFI_APPLICATION 10	Extensible Firmware Interface (EFI) application.
IMAGE_SUBSYSTEM_EFI_BOOT_SERVICE_DRIVER 11	EFI driver with boot services.
IMAGE_SUBSYSTEM_EFI_RUNTIME_DRIVER 12	EFI driver with run-time services.
IMAGE_SUBSYSTEM_EFI_ROM 13	EFI ROM image.
IMAGE_SUBSYSTEM_XBOX 14	Xbox system.
IMAGE_SUBSYSTEM_WINDOWS_BOOT_APPLICATION 16	Boot application.

DllCharacteristics

The DLL characteristics of the image. The following values are defined.

Value	Meaning
0x0001	Reserved.
0x0002	Reserved.
0x0004	Reserved.
0x0008	Reserved.
IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE 0x0040	The DLL can be relocated at load time.
IMAGE_DLLCHARACTERISTICS_FORCE_INTEGRITY 0x0080	Code integrity checks are forced.
IMAGE_DLLCHARACTERISTICS_NX_COMPAT 0x0100	The image is compatible with data execution prevention (DEP).
IMAGE_DLLCHARACTERISTICS_NO_ISOLATION 0x0200	The image is isolation aware, but should not be isolated.
IMAGE_DLLCHARACTERISTICS_NO_SEH 0x0400	The image does not use structured exception handling (SEH). No handlers can be called in this image.
IMAGE_DLLCHARACTERISTICS_NO_BIND 0x0800	Do not bind the image.
0x1000	Reserved.
IMAGE_DLLCHARACTERISTICS_WDM_DRIVER 0x2000	A WDM driver.
0x4000	Reserved.
IMAGE_DLLCHARACTERISTICS_TERMINAL_SERVER_AWARE 0x8000	The image is Terminal Server aware.

SizeOfStackReserve

The number of bytes to reserve for the stack. Only the memory specified by the SizeOfStackCommit member is committed at load time; the rest is made available one page at a time until this reserve size is reached.

SizeOfStackCommit

The number of bytes to commit for the stack.

SizeOfHeapReserve

The number of bytes to reserve for the local heap. Only the memory specified by the SizeOfHeapCommit member is committed at load time; the rest is made available one page at a time until this reserve size is reached.

SizeOfHeapCommit

The number of bytes to commit for the local heap.

LoaderFlags

This member is obsolete.

NumberOfRvaAndSizes

The number of directory entries in the remainder of the optional header. Each entry describes a location and size.

DataDirectory

A pointer to the first IMAGE_DATA_DIRECTORY structure in the data directory.

Remarks

The number of directories is not fixed. Check the NumberOfRvaAndSizes member before looking for a specific directory.

The actual structure in Winnt.h is named IMAGE_OPTIONAL_HEADER32 and IMAGE_OPTIONAL_HEADER is defined as IMAGE_OPTIONAL_HEADER32. However, if _WIN64 is defined, then IMAGE_OPTIONAL_HEADER is defined as IMAGE_OPTIONAL_HEADER64.

typedef struct _IMAGE_OPTIONAL_HEADER64 {
 WORD        Magic;
 BYTE        MajorLinkerVersion;
 BYTE        MinorLinkerVersion;
 DWORD       SizeOfCode;
 DWORD       SizeOfInitializedData;
 DWORD       SizeOfUninitializedData;
 DWORD       AddressOfEntryPoint;
 DWORD       BaseOfCode;
 ULONGLONG   ImageBase;
 DWORD       SectionAlignment;
 DWORD       FileAlignment;
 WORD        MajorOperatingSystemVersion;
 WORD        MinorOperatingSystemVersion;
 WORD        MajorImageVersion;
 WORD        MinorImageVersion;
 WORD        MajorSubsystemVersion;
 WORD        MinorSubsystemVersion;
 DWORD       Win32VersionValue;
 DWORD       SizeOfImage;
 DWORD       SizeOfHeaders;
 DWORD       CheckSum;
 WORD        Subsystem;
 WORD        DllCharacteristics;
 ULONGLONG   SizeOfStackReserve;
 ULONGLONG   SizeOfStackCommit;
 ULONGLONG   SizeOfHeapReserve;
 ULONGLONG   SizeOfHeapCommit;
 DWORD       LoaderFlags;
 DWORD       NumberOfRvaAndSizes;
 IMAGE_DATA_DIRECTORY DataDirectory[IMAGE_NUMBEROF_DIRECTORY_ENTRIES];
} IMAGE_OPTIONAL_HEADER64, *PIMAGE_OPTIONAL_HEADER64;

Requirements

See Also

ImageHlp Structures
IMAGE_DATA_DIRECTORY

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Build date: 9/25/2007