首先是一个adc10的模块程序如下，不懂之处已标红，望有人给我解释解释，尤其是那个控制器1左移12是有什么意义，非常不解，谢谢了！
/*
 * ADC10Conversion(unsigned char):
 * 功能: adc10启动并根据传入采样通道完成一次采样
 * 输入: 要采样的adc10的通道
 * 输出: 一次完成的采样值
**/
unsigned int ADC10Conversion(unsigned char inch)
{
    //if(inch > 7)     /* ADC10 channel #0~7*/
        //return 0;
    if(inch > 7 && inch < 15)
        return 0;
   
    ADC10CTL0 &= ~ADC10SC;
    ADC10CTL0 &= ~ENC;
    ADC10CTL1  = ((unsigned int)inch << 12) + ADC10SSEL_3;     //input channel + clock source select SMCLK
    ADC10AE0   = BIT0 << inch;  //Analog input enabled
    ADC10CTL0 |= ENC + ADC10SC; //adc10 enabled + start sample and conversion
    ADC10CTL0 |= ADC10SC;
    while(ADC10CTL1 & ADC10BUSY);
    return ADC10MEM;
}