The carry from bit3 to bit4 needed for adding packed binary coded decimal number correctly, where two binary coded decimal digits reside in one8-bit byte. 在两个用二进制编码的十进制数字同居于一个8位字节内的情况下，为了正确地对装配型二进制编码的十进制数进行相加所需的从第3位到第4位的进位。
A binary-coded decimal code for representing decimal numbers in which each decimal digit is represented by seven binary digits which are coefficients of 8,6,4,2,0,1,0, respectively. 用于表示十进制数的一种二进制编码的十进制码，其中每位十进制数用七位二进制数来表示，它们分别是8,6,4,2,0,1和0的系数。
