After all this, the binary representation of 8.5 is:
01000001000010000000000000000000
34 COMPUTER ORGANIZATION [CHAP. 3
The sign bit is 0 (positive), the exponent field has the value 130 (10000010), and the mantissa field has the
value 0001 (and lots of following zeros).
As you can imagine, computing with real numbers requires the computer to do more work than
computing with integers. The mantissa and exponent fields must be considered appropriately in all mathematical
operations. In fact, some computers have special floating-point processor hardware to speed such
calculations.
CHARACTER FORMATS
We think of computing as work with numbers, but in fact most computing operates on character data rather
than numeric data??”names, addresses, order numbers, gender, birthdates, etc. are usually, or often, represented
by strings of characters rather than numeric values.
Characters are mapped to integer numbers. There have been many character??“to-integer mappings
over the years. IBM invented a mapping called binary coded decimal (BCD), and later extended
BCD interchange coded (EBCDIC), which became a de facto standard with IBM??™s early success in the
computer market.
The American standard American Standard Code for Information Interchange (ASCII) was defined in the
1960s and became the choice of most computer vendors, aside from IBM.
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