Control Data Cyber 170 State Hardware Reference Manual page 186

CP Programming
Negative exponents a r e expressed i n complement form by beginning with a
b i a s of
1777 (-0) and then s u b t r a c t i n g the magnitude of the exponent. he range of
negative exponents i s negative 0000 through negative 1777.
I n packed
form, the
range i s 1777 through 0000.
When the c o e f f i c i e n t i s negative, t h e packed negative exponent i s complemented
t o become 6000 through 7777.
Examples of packed and unpacked floating-point numbers a r e shown i n o c t a l
n o t a t i o n t o i l l u s t r a t e t h e packing process.
b a m p l e s ' l
and 2
a r e d i f f e r e n t
forms of t h e i n t e g e r p o s i t i v e 1. Fxample 3 i s p o s i t i v e 100 (decimal), and
example
4 i s
negative 100 (decimal).
Examples 5 and 6 a r e l a r g e and small
p o s i t i v e numbers. The unpacked values a r e shown as they might appear i n t h e X
and B r e g i s t e r s p r i o r t o a pack operation.
The packed -0 exponent i s not used f o r normal operation. I n s t e a d , 1777 i s used
i n d i c a t e t h e s p e c i a l e r r o r c o n d i t i o n of i n d e f i n i t e .
Unpacked c o e f f i c i e n t
Unpacked exponent
Packed format
Unpacked c o e f f i c i e n t
Unpacked exponent
Packed format
Unpacked c o e f f i c i e n t
Unpacked exponent
Packed format
Unpacked c o e f f i c i e n t
Unpacked exponent
Packed format
Unpacked c o e f f i c i e n t
Unpacked exponent
Packed format
Unpacked c o e f f i c i e n t
Unpacked exponent
Packed format