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The WriteProcessMemory function writes data to an area of memory in a specified process. The entire area to be written to must be accessible, or the operation fails.

Declare Function WriteProcessMemory Lib "kernel32" (ByVal hProcess As Long, ByVal lpBaseAddress As Any, ByVal lpBuffer As Any, ByVal nSize As Long, ByVal lpNumberOfBytesWritten As Long) As Long

Operating Systems Supported
Requires Windows NT 3.1 or later; Requires Windows 95 or later


Parameter Information
- hProcess
[in] Handle to the process whose memory is to be modified. The handle must have PROCESS_VM_WRITE and PROCESS_VM_OPERATION access to the process.

- lpBaseAddress
[in] Pointer to the base address in the specified process to which data will be written. Before any data transfer occurs, the system verifies that all data in the base address and memory of the specified size is accessible for write access. If this is the case, the function proceeds; otherwise, the function fails.

- lpBuffer
[in] Pointer to the buffer that contains data to be written into the address space of the specified process.

- nSize
[in] Specifies the requested number of bytes to write into the specified process.

- lpNumberOfBytesWritten
[out] Pointer to a variable that receives the number of bytes transferred into the specified process. This parameter is optional. If lpNumberOfBytesWritten is NULL, the parameter is ignored.

Return Values
If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError. The function will fail if the requested write operation crosses into an area of the process that is inaccessible.

Last update: 07 April 2006