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Unformatted text preview: EBCDIC. Because each decimal digit has a zone with it, numbers
coded in EBCDIC are called zoned decimal numbers. Numeric data input into the
computer are usually zoned decimal numbers. Printers can print only those numeric
characters that are in a zoneddecimal format.
Numeric Value EBCDIC Sign Indicator 345
+345
345 F3F4F5
F3F4C5
F3F4D5 F for unsigned
C for positive
D for negative Figure 4.4. Numeric values in EBCDIC in Hexadecimal notation.
However, most computers cannot perform arithmetic operations on zoneddecimal data.
Thus, before any arithmetic operation can be performed, the data must be converted to a
format on which arithmetic operations are possible. One such acceptable format is the
packed decimal format. The following steps are used to convert a zoned decimal nunoer
to a packed decimal number:
Step 1: The zone half and the digit half of the rightmost byte are reversed. This moves
the sign to the extreme right of the number.
Step 2: All remaining zones are dropped out. Figure 4.5 illustrates the conversion process
of zoned decimal data to packed data.
Numeric Value
Zoned Format Packed Format
345
F3F4F5
345F
+345
F3F4C5
345C
345
F3F4D5
345D
3456
F3F4F5F6
03456F
Figure 4.5. Zoned and packed decimal numbers.
It may be observed that packed data requires fewer number of bytes (group of 8 bits) as
compared to zoned data. In the zoned format, there is only one digit per byte (each digit
along with the zone requires 8 bits). But there are two digits in each byte in the packed
format (each digit requires 4 bits). If the packing process does not completely fill a byte,
it is filled with a zero. For example, the zoned data F3F4F5F6 will convert to packed data
03456F. Observe that in this example, the zoned data requires 4 bytes and the packed
data requires only 3 bytes
Example 4.3.
Using binary notation, write the EBCDIC coding for the word BIT. How many bytes are
required for this representation?
Solution:
B = 1100 0010 in EBCDIC binary notation I = 1100 1001 in EBCDIC...
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This document was uploaded on 04/07/2014.
 Spring '14

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