form1.cs

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			this.btn_c.Text = "C";
			this.btn_c.Click += new System.EventHandler(this.btn_Oper);
			// 
			// btn_ce
			// 
			this.btn_ce.Font = new System.Drawing.Font("宋体", 9F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(134)));
			this.btn_ce.Location = new System.Drawing.Point(104, 40);
			this.btn_ce.Name = "btn_ce";
			this.btn_ce.Size = new System.Drawing.Size(80, 32);
			this.btn_ce.TabIndex = 21;
			this.btn_ce.Text = "CE";
			this.btn_ce.Click += new System.EventHandler(this.btn_Oper);
			// 
			// btn_bak
			// 
			this.btn_bak.Font = new System.Drawing.Font("宋体", 9F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(134)));
			this.btn_bak.Location = new System.Drawing.Point(16, 40);
			this.btn_bak.Name = "btn_bak";
			this.btn_bak.Size = new System.Drawing.Size(80, 32);
			this.btn_bak.TabIndex = 22;
			this.btn_bak.Text = "backspace";
			this.btn_bak.Click += new System.EventHandler(this.btn_Oper);
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
			this.ClientSize = new System.Drawing.Size(292, 261);
			this.Controls.Add(this.btn_bak);
			this.Controls.Add(this.btn_ce);
			this.Controls.Add(this.btn_c);
			this.Controls.Add(this.btn_mul);
			this.Controls.Add(this.btn_div);
			this.Controls.Add(this.btn_sub);
			this.Controls.Add(this.btn_sqt);
			this.Controls.Add(this.btn_add);
			this.Controls.Add(this.btn_rev);
			this.Controls.Add(this.btn_eql);
			this.Controls.Add(this.btn_dot);
			this.Controls.Add(this.btn_sign);
			this.Controls.Add(this.btn_0);
			this.Controls.Add(this.btn_3);
			this.Controls.Add(this.btn_2);
			this.Controls.Add(this.btn_1);
			this.Controls.Add(this.btn_6);
			this.Controls.Add(this.btn_5);
			this.Controls.Add(this.btn_4);
			this.Controls.Add(this.btn_9);
			this.Controls.Add(this.btn_8);
			this.Controls.Add(this.btn_7);
			this.Controls.Add(this.txtBox);
			this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
			this.Icon = ((System.Drawing.Icon)(resources.GetObject("$this.Icon")));
			this.MaximizeBox = false;
			this.Menu = this.mainMenu1;
			this.Name = "Form1";
			this.Text = "计算器";
			this.Load += new System.EventHandler(this.Form1_Load);
			this.ResumeLayout(false);

		}
		#endregion

		#region 各和常数变量的声明
		public const int NULL = 0;	  // 定义操作码
		public const int ADD = 1;     //表示加
		public const int SUB = 2;     //减
		public const int MUL = 3;     //乘
		public const int DIV = 4;    //除
		public const int SQRT = 5;   //求平方根
		public const int NODOT  = 0;	 // 定义是否点击了小数点,0为没点
		public const int HASDOT = 1;     //定义是否点击了小数点,1为点了
		private double res = 0;		 // 记录结果数
		private double tmp = 0;		 // 当前输入的操作数
		private int opt = NULL;		 // 记录操作码
		private int dot = NODOT;	// 记录是否点击了小数点,初始值设为0为没有点
		private int num = 0;		// 记录输入操作数的个数
		private int dotnum = 0;		// 记录小数点部分的个数		
		string strOper;            //获取操作符
		#endregion
		/// <summary>
		/// 应用程序的主入口点。
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}

		  
        #region 获取操作数事件
		private void btn_0_Click(object sender, System.EventArgs e)
		{
			System.Windows.Forms.Button btnTmp;
			double i;

			btnTmp = sender as System.Windows.Forms.Button;  //用来判断事件是否是按键操作			
			if (btnTmp != null)
			{
				if (dot == NODOT)    // 没有点击小数点
				{					
					i = double.Parse(btnTmp.Tag.ToString()); //取用户自定义的控件关联数,并转换成double型
					tmp = tmp * 10 + i;   //按键的先后位数依次减少10倍，原数升位再加上新数作为个位
					txtBox.Text = tmp.ToString();   //将其转化成文本显示
				}
				else   // 点击了小数点
				{					
					dotnum++;    //记录小数点部分的个数
					// 生成小数部分的新的数值
					i = double.Parse(btnTmp.Tag.ToString()) / System.Math.Pow(10,dotnum);
					tmp = tmp + i;  //将小数点后的值加到当前操做数
					txtBox.Text = tmp.ToString();
				}
			}
		
		}

		#endregion

        #region 获取操作符
		private void btn_Oper(object sender, System.EventArgs e)
		{
			Button tmp1=(Button)sender;
			strOper=tmp1.Text;

			/*添加*/
			switch (strOper)
			{ 
				case "/":       //除法运算
					if(opt!=NULL&&opt!=DIV)  //用来做连运算，实现上一次计算，近似等于等号
					{
						calc();
					}
					opt = DIV;
					if (num != 0)  //判断操作数的个数,如果两个就做二元运算
					{
						if (tmp != 0)
							res = res / tmp;
						else
						{
							txtBox.Text="零不能做除数";
							break;
						}

					}
					else
						res = tmp;
					num++;					  
					tmp = 0;
					txtBox.Text = res.ToString();
					dot = NODOT;
					break;

				case "*":
					// 乘法运算
					if(opt!=NULL&&opt!=MUL)
					{
						calc();
					}

					opt = MUL;
					
					if (num!= 0 )     //判断操作数的个数,如果两个就做二元运算	
					{
						if(tmp!=0)
							res = res * tmp;
					}
					else
						res = tmp;
					
					num++;					                  
					tmp = 0;
					txtBox.Text = res.ToString();
					dot = NODOT;
					break;

				case "+":            //加法运算	
					if(opt!=NULL&&opt!=ADD)  //非首次运算或连加
					{
						calc();
					}
					opt = ADD;
					if (num != 0)    //判断操作数的个数,如果两个就做二元运算
						res = res + tmp;
					else
						res = tmp;
					num++;					
					tmp = 0;
					txtBox.Text = res.ToString();
					dot = NODOT;
					break;

				case "-":        //减法运算	
					if(opt!=NULL&&opt!=SUB)
					{
						calc();
					}
					opt = SUB;
					if (num != 0)    //判断操作数的个数,如果两个就做二元运算
						res = res - tmp;
					else
						res = tmp;
					num++;					 
					tmp = 0;
					txtBox.Text = res.ToString();
					dot = NODOT;
					break;

				case "sqt":     //平方根运算				
					if (tmp > 0)  //要求操作数大于0
					{
						tmp = Math.Sqrt(tmp);
						
					}					
					txtBox.Text =tmp.ToString();
					num++;						
					dot = NODOT;				
					break;

				case "1/x":  //倒数运算
					if (tmp != 0)
					{
						tmp = 1 / tmp;
						txtBox.Text = tmp.ToString();
						
					}
					else						
						txtBox.Text ="零不能为除数";									
					dot = NODOT;
					break;

				case ".":
					// 点击了小数点
					if(dot==HASDOT)
						return;
					else
					{
						dot = HASDOT;
						dotnum = 0;
					}					
					break;

				case "+/-":
					// 点击了符号运算
					if(tmp!=0)     //对运算数取反
					{
						tmp = -tmp;
						txtBox.Text = tmp.ToString();
					}
					else
					{
						res=-res;	//对结果取反					
						txtBox.Text = res.ToString();	
					}
					dot = NODOT;
					break;	

				case "C":         //清除运算
					res = 0;		 
					tmp = 0;		 
					opt = NULL;		 
					dot = NODOT;	
					num = 0;		
					dotnum = 0;		//恢复初始设定
					txtBox.Text="0.";
					break;

				case "CE":         //清除最后输入的计算数					
					tmp = 0;		 // 清除当前输入的操作数					
					txtBox.Text="0.";
					break;

				case "backspace":         //清除最后输入数字的最后的位数
					string showNumber;
					showNumber=txtBox.Text;
					if(txtBox.Text.Length>1)
					{
						txtBox.Text=showNumber.Substring(0,showNumber.Length-1);
						tmp=double.Parse(txtBox.Text);
					}
					else
					{
						txtBox.Text="0.";
						tmp=0;
					}
					break;

			}
		
		}
        #endregion

		#region 等于事件和等于事件的处理		
		private void btn_eql_Click(object sender, System.EventArgs e)
		{		
			calc();
		}
		//等于的算法
		private void calc()
		{		
			if (num == 0 )    //判断是否有操作数,没有就返回0
			{
				res = 0;
				tmp = 0;
				txtBox.Text = res.ToString();
				return;
			}

			switch (opt)  //找到对应的运算符进行相应的计算
			{
					// 加法
				case ADD:
					res = res + tmp;					
					break;

					// 减法
				case SUB:
					res = res - tmp;					
					break;

					// 乘法
				case MUL:
					res = res * tmp;					
					break;

					// 除法
				case DIV:
					res = res / tmp;					
					break;
				
					// 求平方根
				case SQRT:
					res = System.Math.Sqrt(tmp);					
					break;

				default:
					return;
			}
			txtBox.Text = res.ToString();   //结果转换成字符形式输出到文本显示屏
			//重要一步---每计算一次都要把中间量重设成初值，否则连续运算出现问题
			opt = NULL;  //运算符清空
			tmp=0;	//清空当前操作数，只有再次输入操作数才进行计算，否则保持原数
			dot = NODOT;  //新一次的计算，小数点的判断从新计算
			
		}
		#endregion
	
		#region 菜单事件
		//复制事件
		private void menuItem_cop_Click(object sender, System.EventArgs e)
		{
		    if(txtBox.SelectionLength>0)
			{
				txtBox.Copy();
			}
		}

		//粘贴事件
		private void menuItem_pas_Click(object sender, System.EventArgs e)
		{
		   txtBox.Paste();
		}

		//打开关于“计算器”的主题--调用windows xp中计算器的帮助
		private void menuItem_hsj_Click(object sender, System.EventArgs e)
		{
		   Help.ShowHelp(this,"C:\\WINDOWS\\Help\\calc.chm");	
		}

        //打开关于“计算器”
		private void menuItem_abt_Click(object sender, System.EventArgs e)
		{
			Form2 fm2=new Form2();
			fm2.Show();
		}
		#endregion

		private void Form1_Load(object sender, System.EventArgs e)
		{
		
		}

		private void txtBox_TextChanged(object sender, System.EventArgs e)
		{
		
		}
	}
}