Pack decimal
Pack decimalWith, numerical value computer,BCDIt is defined in the base. At the beginningZoned decimal numberSo it had expressed, but 1 byte (the = 8 bits) it requires concerning 1 column, takes the place. Then, numerical value is allotted to also the zone bit which has become wasteful, 2 columns those which it tries to be able to express are pack decimal at 1 byte.
Are expressed at the numerical bit 4 columns of 1 columns of decimal, but in order to judge correct several negative several, 4 bits which are called the sign binary digit, are added to the end of numerical value. As for the sign binary digit, 12, 13 is allotted to negative number in correct number.
Structure
Below, when it expresses +789 as example, structure of pack decimal is shown.
| 0111 | 1000 | 1001 | 1100 |
| Numerical bit | Numerical bit | Numerical bit | Sign binary digit |
Example
| +1234 | 0001 0010 0011 0100 1100 |
| -1234 | 0001 0010 0011 0100 1101 |
