Data Format .
Guard Digit .
Number RepresentationNormalization Instructions .
ADD NORMALIZED
ADD UNNORMALIZED
COMPAREDIVIDE HALVE . LOAD LOAD AND TEST LOAD COMPLEMENT. LOAD NEGATIVE. LOAD POSITIVE LOAD ROUNDED MULTIPLY. STORE .
SUBTRACT NORMALIZED
SUBTRACT UN NORMALIZED
Contents
The floating-point instructions are used to perform
calculations on operands with a wide rangeof mag
nitude and to yield results scaled to preserve preci
sion.
A floating-point number consists of a signed ex
ponent, represented by the characteristic, and a
signed fraction. The quantity expressed by this
number is the product of the fraction and the num
ber 16 raised to the power of the exponent. The
exponent is expressed in excess-64 binary notation
(see "NumberRepresentation"); the fraction is ex
pressed as a hexadecimal number having a radix
point to the left of the high-order digit.
To avoid unnecessary storing and loading opera
tions for results and operands, four floating-point
registers are provided. The floating-point instruc
tions provide for the loading, rounding, adding, sub
tracting, comparing, multiplying, dividing, and stor
ing, as well as the sign control, of short, long, and
extended operands.Short operands generally provide
faster processing and require less storage than long
or extended operands.On the other hand, long and
extended operands provide greater precision in com
putation. Operations may be either register to regis
ter or storage to register.
For addition, subtraction, multiplication, and divi
sion, instructions are provided that generate normal
ized results. Normalized results preserve the highest
Floating-Point Instructions
157
158
159
159160 160 162
163
163
164
165
165
165
166
166
166
167
168
169
169
precision in the operation. For addition and subtrac
tion, instructions are also provided that generate
unnormalized results. Normalized and unnormalized
operands may be used in any floating-point opera
tion.
The condition code is set as a result of all sign
control, add, subtract, and compare operations.
The rounding and extended-operand instructions
are part of the extended-precision floating-point
feature. The other floating-point instructions and the
registers are part of the floating-point feature.
Data Format
Floating-point data occupies a fixed-length format,
which may be either a four-byte (short) format, an
eight-byte (long) format, or a 16-byte (extended)
format. The short and long formats may be designat
edas operands both in main storage and in the
floating-point registers, whereas the extended for
mats can be designated only in the floating-point
registers.
The floating-point registers are numbered0, 2, 4,
and 6. Designation of an odd-numbered register in
the Rt or R2 field of a floating-point instruction
causes the operation to be suppressed and a program
interruption for specification exception to occur.
Floating-Point Instructions 157
Guard Digit .
Number Representation
ADD NORMALIZED
ADD UNNORMALIZED
COMPARE
SUBTRACT NORMALIZED
SUBTRACT UN NORMALIZED
Contents
The floating-point instructions are used to perform
calculations on operands with a wide range
nitude and to yield results scaled to preserve preci
sion.
A floating-point number consists of a signed ex
ponent, represented by the characteristic, and a
signed fraction. The quantity expressed by this
number is the product of the fraction and the num
ber 16 raised to the power of the exponent. The
exponent is expressed in excess-64 binary notation
(see "Number
pressed as a hexadecimal number having a radix
point to the left of the high-order digit.
To avoid unnecessary storing and loading opera
tions for results and operands, four floating-point
registers are provided. The floating-point instruc
tions provide for the loading, rounding, adding, sub
tracting, comparing, multiplying, dividing, and stor
ing, as well as the sign control, of short, long, and
extended operands.
faster processing and require less storage than long
or extended operands.
extended operands provide greater precision in com
putation. Operations may be either register to regis
ter or storage to register.
For addition, subtraction, multiplication, and divi
sion, instructions are provided that generate normal
ized results. Normalized results preserve the highest
Floating-Point Instructions
157
158
159
159
163
163
164
165
165
165
166
166
166
167
168
169
169
precision in the operation. For addition and subtrac
tion, instructions are also provided that generate
unnormalized results. Normalized and unnormalized
operands may be used in any floating-point opera
tion.
The condition code is set as a result of all sign
control, add, subtract, and compare operations.
The rounding and extended-operand instructions
are part of the extended-precision floating-point
feature. The other floating-point instructions and the
registers are part of the floating-point feature.
Data Format
Floating-point data occupies a fixed-length format,
which may be either a four-byte (short) format, an
eight-byte (long) format, or a 16-byte (extended)
format. The short and long formats may be designat
ed
floating-point registers, whereas the extended for
mats can be designated only in the floating-point
registers.
The floating-point registers are numbered
and 6. Designation of an odd-numbered register in
the Rt or R2 field of a floating-point instruction
causes the operation to be suppressed and a program
interruption for specification exception to occur.
Floating-Point Instructions 157