In the computer world, the binary number systems the system used. All data is stored and manipulated inside the computer in binary．That is, within the computer all data is reduced to 1's and 0's．This 1'sand 0's are stored in logic circuits called registers, or they are stored in memory. The size of a register or memory location varies according to the kind of computer used.   

　　Today's microcomputers will store either 8 or 16binary digits in each location. Large computers may store as many as 125 binary digits in each location.     

　　We normally enter data into the computer in some number system other than binary because entering data in binary is too time-consuming and too prone to error—too many 1's and 0's．Data is entered into the computer using the decimal, octal, or hexadecimal number systems．Octal and hexadecimal are used most often because they are more closely related to binary than is the decimal system. It Is Important to our understanding of these number system-that we know how they are related one to another.

翻译：

数据和数系
   
　　我们大家都知道并理解十进制数系，这是我们每天使用的数系。

　　在计算机世界中，所用的数系是二进制数系。所有的数据在计算机内部都是以二进制（形式）存储和处理的，就是说，在计算机内部所有数据都归结为1和0这些1和 0存储在称为寄存器的逻辑电路中，或者它们被存储在存储器中，寄存器或存储器单元的大小，按照所用的计算机的种类而变化。  

　　今天的微型计算机在其每个存储单元中，将存储8位或16位二进制数字，大型计算机在其每个字存储单元中可以存储多达125个二进制数字。   

　　我们通常是以某种数系往计算机中输入数据，而不用二进制系，因为以二进制数系输入数据费时间，并且容易出错一一1和0太多，数据在输入计算机时，是用进制、八进制或十六进制数系（进行的）。八进制及十六进制是最常用的，因为它们比十进制数系更接近于二进制数系。理解这些数系是很重要的，因为我们可了解它彼此之间是怎样联系的。

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。