Keyboard Events Simulation using keybd_event() function

Introduction

Simulation of a keyboard input is a well known concept for those who are all familiar with Visual Basic. SendKeys() in Visual Basic does all the things, if you want to do anything without keyboard. But what is in SendKeys() function? What does it do? Can we do such a thing with Visual C++? This article is the answer. I think this will be useful for beginners who are all just trying to do something different with VC++. Let us get into the steps…

Function Syntax

void keybd_event(BYTE bVirtualKey, BYTE bScanCode, 
                         DWORD dwFlags, DWORD dwExtraInfo);

• bVirtualKey //Virtual Keycode of keys. E.g., VK_RETURN, VK_TAB…
• bScanCode //Scan Code value of keys. E.g., 0xb8 for “Left Alt” key.
• dwFlags //Flag that is set for key state. E.g., KEYEVENTF_KEYUP.
• dwExtraInfo //32-bit extra information about keystroke.

Function Details:

• bVirtualKey

  Virtual keycode that has to be send as key input. The following are the available predefined virtual key codes:

  VK_NUMPAD7	0x67	VK_BACK	0x08
  VK_NUMPAD8	0x68	VK_TAB	0x09
  VK_NUMPAD9	0x69	VK_RETURN	0x0D
  VK_MULTIPLY	0x6A	VK_SHIFT	0x10
  VK_ADD	0x6B	VK_CONTROL	0x11
  VK_SEPARATOR	0x6C	VK_MENU	0x12
  VK_SUBTRACT	0x6D	VK_PAUSE	0x13
  VK_DECIMAL	0x6E	VK_CAPITAL	0x14
  VK_DIVIDE	0x6F	VK_ESCAPE	0x1B
  VK_F1	0x70	VK_SPACE	0x20
  VK_F2	0x71	VK_END	0x23
  VK_F3	0x72	VK_HOME	0x24
  VK_F4	0x73	VK_LEFT	0x25
  VK_F5	0x74	VK_UP	0x26
  VK_F6	0x75	VK_RIGHT	0x27
  VK_F7	0x76	VK_DOWN	0x28
  VK_F8	0x77	VK_PRINT	0x2A
  VK_F9	0x78	VK_SNAPSHOT	0x2C
  VK_F10	0x79	VK_INSERT	0x2D
  VK_F11	0x7A	VK_DELETE	0x2E
  VK_F12	0x7B	VK_LWIN	0x5B
  VK_NUMLOCK	0x90	VK_RWIN	0x5C
  VK_SCROLL	0x91	VK_NUMPAD0	0x60
  VK_LSHIFT	0xA0	VK_NUMPAD1	0x61
  VK_RSHIFT	0xA1	VK_NUMPAD2	0x62
  VK_LCONTROL	0xA2	VK_NUMPAD3	0x63
  VK_RCONTROL	0xA3	VK_NUMPAD4	0x64
  VK_LMENU	0xA4	VK_NUMPAD5	0x65
  VK_RMENU	0xA5	VK_NUMPAD6	0x66

  Character key can be converted into virtual key using VkKeyScan(TCHAR ch) function.

• bScanCode

  Scan code is the hardware key code for the key (make and break codes). The following are the available scan codes (break code will be used in this parameter).

  

  

• dwFlags

  A set of flag bits that specify various aspects of function operation. An application can use any combination of the following predefined constant values to set the flags.

  Value	Meaning
  KEYEVENTF_EXTENDEDKEY	If specified, the scan code was preceded by a prefix byte having the value 0xE0 (224).
  KEYEVENTF_KEYUP	If specified, the key is being released. If not specified, the key is being depressed.

• dwExtraInfo

  32-bit extra information along with the keyboard input.

  

Example Code

// Simulating a Alt+Tab keystroke

keybd_event(VK_MENU,0xb8,0 , 0); //Alt Press

keybd_event(VK_TAB,0x8f,0 , 0); // Tab Press

keybd_event(VK_TAB,0x8f, KEYEVENTF_KEYUP,0); // Tab Release

keybd_event(VK_MENU,0xb8,KEYEVENTF_KEYUP,0); // Alt Release


// Simulating a Ctrl+A keystroke

keybd_event(VK_CONTROL,0x9d,0 , 0); // Ctrl Press

keybd_event(VkKeyScan(‘A’),0x9e,0 , 0); // ‘A’ Press

keybd_event(VkKeyScan(‘A’),0x9e, KEYEVENTF_KEYUP,0); // ‘A’ Release

keybd_event(VK_CONTROL,0x9d,KEYEVENTF_KEYUP,0); // Ctrl Release

Conclusion

This article may not be that much detailed. None of the articles can satisfy one's expectations. But, each article should be a seed for your technical growth. Thus, I believe that this would be a seed. Thank you all.