error with Static Library code

hi all,
i'm learning the book "Teach Yourself Visual C++ 6 in 21 days" , and i'm in Chapter 16 - Creating Your Own Classes and Modules . I did everything like it said but i've an error. This Static Library project has 2 classes , 1 class , called CLine , is added from other project and 1 class , called CModArt , is added in this project .
So this is the code to creat new line in CModArt class :

Code:

void CModArt::NewLine()
{
	int lNumLines;
	int lCurLine;
	int nCurColor;
	UINT nCurWidth;
	CPoint pTo;
	CPoint pFrom;

	//Normalize the rectangle before determining the width and height
	m_rDrawArea.NormalizeRect();
	//Get the area width and height
	int lWidth = m_rDrawArea.Width();
	int lHeight = m_rDrawArea.Height();

	//Determine number of parts to this squiggle
	lNumLines = rand() % 100;
	//Are there any part in squiggle
	if (lNumLines > 0)
	{
		//Determine color
		nCurColor = rand() % 8;
		//Determine the pen width
		nCurWidth = (rand() % 8) + 1;
		//Determine the start point for the squiggle
		pFrom.x = (rand() % lWidth) + m_rDrawArea.left;
		pFrom.y = (rand() % lHeight) + m_rDrawArea.top;

		//Loop through number of sequents
		for (lCurLine=0; lCurLine<lNumLines; lCurLine++)
		{
			pTo.x = ((rand() % 20) - 10) + pFrom.x;
			pTo.y = ((rand() % 20) - 10) + pFrom.y;

			//Creat a new line
			//CLine *pLine = new CLine(pFrom, pTo, nCurWidth, m_crColors[nCurColor]);
			CLine *pLine = new CLine(pFrom, pTo, m_crColors[nCurColor]);

			try
			{
				//try to add new line
				m_oaLines.Add(pLine);
			}

			//Check did we run into memory exception
			catch (CMemoryException *perr)
			{
				//Notice user the message
				AfxMessageBox("Out of memory", MB_ICONSTOP | MB_OK);
				//Did we creat a new line
				if (pLine)
				{
					delete pLine;
					pLine = NULL;
				}
				//Delete the exception
				perr->Delete();
			}
			//Set the starting point to the end point;
			pFrom = pTo;
		}
	}
}

and this is the error :

...\ModArt.cpp(82) : error C2065: 'CLine' : undeclared identifier

and this is the 82 line :

Code:

CLine *pLine = new CLine(pFrom, pTo, m_crColors[nCurColor]);

Thanx 4 all ur helps!

> ...\ModArt.cpp(82) : error C2065: 'CLine' : undeclared identifier
Do you have a header file for the CLine class? It sounds like you need to:

Code:

#include "cline.h"

at the top of ModArt.cpp. Or if you don't have a header for CLine, I guess you'd have to include cline.cpp.

oh , i fixed this bug but i dont understand why . Because before that , I already have include "cline.h" in ModArt.cpp . But now when i also include "cline.h" in ModArt.h , it work gud?
so wat prob here cus i think i just need to include "cline.h" in ModArt.cpp , no need in ModArt.h ?

thanx 4 all ur helps!