计算机专业英语摘要.pptVIP

计算机专业英语 2-* 2.3.4 Multibyte Data Organization In little endian, the order is reversed. The least significant byte is stored in location X, the next byte in location X+1, and so on. The same value, in little endian format, is shown in Table 2-1(b). 依照低位优先格式，顺序正好相反。最低字节存储在单元X中，次字节存储在单元X+1中，依次类推。上例中的同一值，以低位优先格式存储，如表2-1(b)所示。 计算机专业英语 2-* 2.3.4 Multibyte Data Organization The same organizations can be used for bits within a byte. In big endian organization, bit 0 is the rightmost bit of a byte: the left most bit is bit 7. In little endian organization, the leftmost bit is bit 0 and bit 7 is the rightmost bit. 同样的组织方式可用于一个字节中的不同位上。在高位优先结构中，位0代表字节中最右边的位，最左边的位是第7位。在低位优先结构中，最左边的位是0，最右边的位是7。 计算机专业英语 2-* 2.3.4 Multibyte Data Organization Which endian organization is used for bytes and words does not impact the performance of the CPU and computer system. As long as the CPU is designed to handle a specific format, neither is better than the other. The main problem comes in transferring data between computers with different endian organizations. For example, if a computer with little endian organization transfers the value 0102 0304H to a computer with big endian organization without converting the data, the big endian computer will read the value as 0403 0201H. There are programs which can convert data files from one format to the other, and some microprocessors have special instructions to perform the conversion. 对于字节和字而言，无论使用哪一种排列组织方式都不会影响CPU和计算机系统的性能。只要设计CPU处理一种特定的格式，就不存在谁比谁强的问题，主要的问题在于具有不同排列组织方式的CPU之间传输数据的问题，例如，如果一个低位优先结构的计算机传输0102 0304H的数据给一个高位优先结构的计算机，而没有转换数据，那么该高位优先结构计算机读出的值为0403 0201H。有程序可以将两种时局文件进行格式转换，并且某些处理器有特殊的指令可以执行这种转换。 计算机专业英语 2-* 2.3.4 Multibyte Data Organization One other issue of concern for multibyte words is alignment. Modern microprocessors can read in more than one byte of data at a time. For example, the Motorola 68040 microprocessor can read in four bytes simultaneously. However, the four bytes must be in consecutive locations that have the same