GE 235 System Manual page 30

During floating point calculations, the data to be operated upon by the internal logic of the AAU
comes from the main memory of the Central Processor. A floating point number occupies two
words of memory storage and assumes the following format:
Word One
Bits
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Word Two
Se
Bits
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Se
=
Sign of Exponent (0
=
plus;
1 =
minus)
Sm= Sign of Mantissa (0
=
plus; 1
=
minus)
Exponent
The binary point i s assumed to be placed before the mantissa. This format produces a binary
number with a 30-bit mantissa and a binaryexponent range of -256 to +255. This i s approximately
equal to a decimal format of a 9-digit mantissa and a decimal exponent range of -76 to +76. The
use of two words allows one of the sign positions to be applied to the exponent which, in turn,
allows the use of the full range of the exponent.
Mantissa
The word format for fixed point double precision words in memory is a s follows:
Word One
Bits 0
1 4
' +
19
S
S
=
Sign of Word One is the Sign of
Fixed Point Double Word
Word Two
Bits 0 l p - l g
S
=
Sign of Word Two