This results in a one to four reduction in the volume

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Unformatted text preview: it can be easily divided into two 4-bit groups. Each of these 4-bit groups can be represented by 1 hexadecimal digit (refer to Chapter 3). Thus, hexadecimal number system is used as shortcut notation for memory dump by computers that use EBCDIC for internal representation of characters. This results in a one-to-four reduction in the volume of memory dump. Figure 4.3 shows the alphabetic and numerical characters in EBCDIC along with their hexadecimal equivalent. Developed by IBM, EBCDIC code is used in most IBM models and in many other computers. Character EBCDIC Code Hexadecimal Equivalent A B C D E F Zone 1100 1100 1100 1100 1100 1100 Digit 0001 0010 0011 0100 0101 0110 Cl C2 C3 C4 C5 C6 G H I 1100 1100 1100 0111 1000 1001 C7 C8 C9 J K L M N 0 P Q R 1101 1101 1101 1101 1101 1101 1101 1101 1101 0001 0010 0011 0100 0101 0110 0111 1000 1001 Dl D2 D3 D4 D5 D6 D7 D8 D9 S T U V w X Y z 1110 1110 1110 1110 1110 1110 1110 1110 0010 0011 0100 0101 0110 0111 1000 1001 E2 E3 E4 E5 E6 E7 E8 E9 . 0 mi 0000 F0 1 mi 0001 Fl 2 mi 0010 F2 3 mi 0011 F3 4 nil 0100 F4 5 mi 0101 F5 6 mi 0110 F6 7 nil 0111 F7 8 nil 1000 F8 9 mi 1001 F9 Figure 4.3. Alphabetic and numeric characters in EBCDIC along with their Hexadecimal eauivalent. Zoned and Packed Decimal Numbers From Figure 4.3 it can be observed that in the EBCDIC code, the digit values are the same as the numeric characters - 0 through 9 (0000 - 1001). But numeric values need some special consideration because we must have a way of indicating whether the number is positive, negative, or unsigned (implies positive). Thus, when a numeric value is represented in EBCDIC, a sign indicator is used in the zone position of the rightmost digit. A sign indicator of hexadecimal C is a plus sign, hexadecimal D is a minus sign, and hexadecimal F means the number is unsigned. Figure 4.4 illustrates the representation of numeric values in EBCDIC. Note that the only zone affected by the sign is the* zone of the rightmost digit. All other zones remain as F, the zone value for numeric characters in...
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This document was uploaded on 04/07/2014.

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