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Multiple Clocks

Introduction This dialog-based application displays several different styles of clocks: analog, binary, decimal, and nixie. Background The Nixie tube was used in electronic instruments mainly in the 1960s thru 1980s. It is a neon-filled vacumn tube with 10 elements that can make the neon glow when any one element is grounded. The tube has a […]

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CodeGuru Staff

Jul 6, 2004

2 minute read

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Introduction
Background
Using the Code
Points of Interest
Credits
History

Introduction

This dialog-based application displays several different styles of clocks: analog, binary, decimal, and nixie.

Background

The Nixie tube was used in electronic instruments mainly in the 1960s thru 1980s. It is a neon-filled vacumn tube with 10 elements that can make the neon glow when any one element is grounded. The tube has a common anode with approximately 175 volts DC applied to it. I think it makes a cool clock.

Using the Code

Several methods used in this code are borrowed from other programmers, some from this site (see Credits). The heart of the binary clock is the _itoa(nTime, ibuff, 2); function, where nTime is any integer contaning the hour, minute, or second. ibuff is a char buffer and the 2 is a base, in this case, binary.

Here is the code to display a simple Decimal clock in the Windows Title Bar.

void CMultiClockDlg::DisplayDecimal()
{
   //
   // Get the current time
   //
   CTime time  = CTime::GetCurrentTime();
   int nSecond = time.GetSecond();
   int nMinute = time.GetMinute();
   int nHour   = time.GetHour();
   if (nHour > 12)
      nHour -= 12;
   CString szStr;
   szStr.Format("MultiClock - %.2d:%.2d:%.2d", nHour, nMinute, nSecond);
   ::SetWindowText(m_hWnd, szStr);
}

Points of Interest

The Binary display is grouped: 4 bits for the hour, and 6 bits for the minutes and seconds. I did this because the hour can only be “01” thru “C” and the minutes/seconds “00” thru “3B”. The nixie clock uses bitmaps (45X64) for each digit; they are diplayed by calling:

void CMultiClockDlg::FormatTm(CDC *pDC, int nTime, int nPos)
{
   int x, y;
   m_bmp.LoadResource(IDB_BITMAP110);
   x = 8 +(m_bmp.GetWidth() * nPos);
   y = 8;
   switch (nTime)
   {
      case 0:
         m_bmp.LoadResource(IDB_BITMAP100);
         m_bmp.DrawDIB(pDC, x, y);
         break;
   }

One thing I found when writing this code was this: DO NOT USE CDC *pDC = GetDC(); in a loop without using RelaseDC(pDC); My first version would run for 15 to 20 minutes and crash because GetDC() uses 4 bytes of memory every time it is called.