KEYWORDS
Binary Coded Decimal（BCD） 二进制编码的十进制，二-十进制
ASCII 美国信息交换用标准代码
EBCDIC 扩展的二-十进制交换码
even-parity 偶检验
odd-parity 奇检验
parity checking 奇偶检验
EXERCISES
1．True／False．
（1）______ The possible symbols in the binary numbering system are 0 to 9．
（2）______The decimal value of 16 is represented in 4 bit BCD as 00010101．
（3）______Alphanumeric versions of BCD commonly use 7，or 8 bits to represent characters．
（4）______ A 6 bit alphanumeric code can represent 128 different characters．
（5）______There are four 8 bit codes in current use．
（6）______ Each 8 bit unit used to code data is called a byte．
（7）______ Eight bit codes are limited to representing 128 different characters．
（8）______ An extra check（or parity）bit is often added to each 7，or 8 bit character represented in storage so that it will be possible to detect coding errors that may occur．
（9）______ The digits that can be found in the binary numbering system are only 0s
and 1s．
（10______ Using BCD we can convert the entire decimal value into a pure binary
form．
2．Fill in the blanks with appropriate words or phrases found behind this exercise．
（1）Every computer stores numbers，letters and characters in a ______ form．
（2）The abbreviation BCB is derived from its full name______．
（3）Using BCD we can convert each decimal number into its binary______．
（4）In addition to four numeric place positions in an 8-bit code there are another four
______positions．
（5）The most popular code used to represent data internally in personal computer is ______．
（6）The main difference between EBCDIC and ASCII-8 is______ positions．
（7）Parity checking has two types，they are ______．
（8）Any character can be represented by using just______of 0 and 1．
a．equivalent
b．even-parity and odd-parity
c．ASCII
d．coded
e．two digits
f．patterns of zone
g．zone bit
h．binary coded decimal
1．（1）f （2）f （3）t （4）f（5）f （6）t （7）f （8）t（9）t （10）f
2．（1）d （2）h （3）a （4）g（5）c （6）f （7）b （8）e