Simulating a keystroke in Win32 (C or C++) using SendInput

This program is a simple example of using the Win32 SendInput function to generate a simulated keystroke. When you run this program, it simply waits 5 seconds and then simulates a press and release of the “A” key on the keyboard.

Here’s the complete source code.

//
// keystroke.c - Pauses, then simulates a key press
// and release of the "A" key.
//
// Written by Ted Burke - last updated 17-4-2012
//
// To compile with MinGW:
//
//		gcc -o keystroke.exe keystroke.c
//
// To run the program:
//
//		keystroke.exe
//
// ...then switch to e.g. a Notepad window and wait
// 5 seconds for the A key to be magically pressed.
//

// Because the SendInput function is only supported in
// Windows 2000 and later, WINVER needs to be set as
// follows so that SendInput gets defined when windows.h
// is included below.
#define WINVER 0x0500
#include <windows.h>

int main()
{
	// This structure will be used to create the keyboard
	// input event.
	INPUT ip;

	// Pause for 5 seconds.
	Sleep(5000);

	// Set up a generic keyboard event.
	ip.type = INPUT_KEYBOARD;
	ip.ki.wScan = 0; // hardware scan code for key
	ip.ki.time = 0;
	ip.ki.dwExtraInfo = 0;

	// Press the "A" key
	ip.ki.wVk = 0x41; // virtual-key code for the "a" key
	ip.ki.dwFlags = 0; // 0 for key press
	SendInput(1, &ip, sizeof(INPUT));

	// Release the "A" key
	ip.ki.dwFlags = KEYEVENTF_KEYUP; // KEYEVENTF_KEYUP for key release
	SendInput(1, &ip, sizeof(INPUT));

	// Exit normally
	return 0;
}

Here’s a screenshot of the console window where I compiled and ran the program.

As soon as I ran the program in the console window, I switched the focus to a Notepad window where the simulated keystroke typed a character, as shown in the following screenshot.