如何取得系統時間

#include time.h

A = clock();

如何動態新增一個影像元件?

TImage *imNew;

imNew = new TImage(this);
imNew->Parent = RScrollBox;
imNew->Left = 2;
imNew->Top = 2;
imNew->Height = IH;
imNew->Width = IW;

上述這段程式, 如果執行時出現下面的錯誤訊息:

[Linker Error] Unresolved external '__fastcall Extctrls::TImage::TImage(Classes::TComponent *)' referenced from...

解決辦法:

'Project | Options | (tab) Packages | (Groupbox) Runtime Packages',

將 Build with Runtime Packages 的勾勾去掉...
　

% operator

我們知道 % operator 就是除法取其餘數的運算子。
例如:

Q = A % 2;

一般來說, Q 值不是 0 就是 1。

不過, 我一直沒有想過如果被除數 A 是負數的時候, 會發生什麼情形? 今天下午我在寫程式時, 就發生了這樣的例子, 害我 debug 很久, 把程式一堆變數的值一一顯示出來看, 才發現這個有趣的問題。原來, 如果被除數 A 是負數的時候, 餘數也會是負數的!
例如:
　
-3 % 2 = -1
　

Audio: 如何播放一段 WAV 檔

Example:
PlaySound("camera.wav",NULL,SND_APPLICATION);

The PlaySound function plays a sound specified by the given filename, resource, or system event.
(A system event may be associated with a sound in the registry or in the WIN.INI file.)

BOOL PlaySound(
LPCSTR pszSound,
HMODULE hmod,
DWORD fdwSound
);

Parameters

pszSound

A string that specifies the sound to play. If this parameter is NULL, any currently playing waveform sound is stopped. To stop a non-waveform sound, specify SND_PURGE in the fdwSound parameter.

Three flags in fdwSound (SND_ALIAS, SND_FILENAME, and SND_RESOURCE) determine whether the name is interpreted as an alias for a system event, a filename, or a resource identifier. If none of these flags are specified, PlaySound searches the registry or the WIN.INI file for an association with the specified sound name. If an association is found, the sound event is played. If no association is found in the registry, the name is interpreted as a filename.

hmod

Handle of the executable file that contains the resource to be loaded. This parameter must be NULL unless SND_RESOURCE is specified in
fdwSound.

fdwSound

Flags for playing the sound. The following values are defined:

SND_APPLICATION

The sound is played using an application-specific association.

SND_ALIAS

The pszSound parameter is a system-event alias in the registry or the WIN.INI file. Do not use with either SND_FILENAME or SND_RESOURCE.

SND_ALIAS_ID

The pszSound parameter is a predefined sound identifier.

SND_ASYNC

The sound is played asynchronously and PlaySound returns immediately after beginning the sound. To terminate an asynchronously played waveform sound, call PlaySound with pszSound set to NULL.

SND_FILENAME

The pszSound parameter is a filename.

SND_LOOP

The sound plays repeatedly until PlaySound is called again with the pszSound parameter set to NULL. You must also specify the SND_ASYNC flag to indicate an asynchronous sound event.

SND_MEMORY

A sound event's file is loaded in RAM. The parameter specified by pszSound must point to an image of a sound in memory.

SND_NODEFAULT

No default sound event is used. If the sound cannot be found, PlaySound returns silently without playing the default sound.

SND_NOSTOP

The specified sound event will yield to another sound event that is already playing. If a sound cannot be played because the resource needed to generate that sound is busy playing another sound, the function immediately returns FALSE without playing the requested sound.
If this flag is not specified, PlaySound attempts to stop the currently playing sound so that the device can be used to play the new sound.

SND_NOWAIT

If the driver is busy, return immediately without playing the sound.

SND_PURGE

Sounds are to be stopped for the calling task. If pszSound is not NULL, all instances of the specified sound are stopped. If pszSound is NULL, all sounds that are playing on behalf of the calling task are stopped.
You must also specify the instance handle to stop SND_RESOURCE events.

SND_RESOURCE

The pszSound parameter is a resource identifier; hmod must identify the instance that contains the resource.

SND_SYNC

Synchronous playback of a sound event. PlaySound returns after the sound event completes.

Return Values

Returns TRUE if successful or FALSE otherwise.

Remarks

The sound specified by pszSound must fit into available physical memory and be playable by an installed waveform-audio device driver. PlaySound searches the following directories for sound files: the current directory; the Windows directory; the Windows system directory; directories listed in the PATH environment variable; and the list of directories mapped in a network. For more information about the directory search order, see the documentation for the OpenFile function.

If it cannot find the specified sound, PlaySound uses the default system event sound entry instead. If the function can find neither the system default entry nor the default sound, it makes no sound and returns FALSE.