Binary Number System   

　　In the binary number system, there are two dig-its：0 and I．The binary system is used for internal computer operations because only two signal levels are required, as opposed to decimal where ten signal levels would be necessary．Because a digit in the units position has a value of 0 or I，numbers greater than 1cause a carry to the next position, each position represents the base raised to a power. In base 10, the units position has a power of 100, the next position 10 l，and so on. Thus, a digit in any position other than the units position has a weight (value) depending on its positioning the number. A 4，for example, has a weight of 4 in the units position, 40 in the 10's position, 400 in the100's position and so on.   

　　In binary, or base 2, the same reasoning applies. The units position has a power of 20, the next position21，and so on. As illustrated in Figure 1-5 a binary digit in any position other than the unit’s position has weight depending on its position in the number. A Has a weight of 1 in the units position, 2 in the 2'sposition, 4 in the 4's position and so on. Binary digits are called bits (a contraction of "binary digits")．Therefore, the digit in the units position is called the east-Significant Bit (LSB) ,and so on until we reach the Most-Significant Bit (MSB)．

翻译：

二进制数

    在二进制数系中有两个数字0和1。二进制用于计算机内部操作，因为它仅需要两种信号电开这与十进制不同，那里将需要1I信号电平。因为在个位上的数字具有0和I的值，所以比I大的数将对下一位产生进位，每个位置代表基的若干次幂。在基为10中，个位具有10“次幂，下一位为10，次幂，等等。这样，在任意位置上（除了个位之外）的数字所具有的权（值）取决于此数字在该数中的位置。例如，4在个位上具有权为4，在十位上具有权40，在百位上具有权400，等等。
   
　　在二进制中（其基为2）应用同样的类推，个位具有权为2。，下一位具有权为2，等等。如图1-5所示，在任意位置上（除了个位之外）的二进制数字所具有的权，取决于此数字在该数中的位置。1在个位上具有的 为1，在2的位置上权为2，在4的位置上权为4，等等。二进制数字称为比特C bit它由”binary digits”缩写而成）。因此，在个位上的数字被称作“最低有效位”(LSB）等等，一直到我们到达“最高有效位”（MSB）为止。