guard digit, is zero, the operands are equal. Neither

operand is changed as a result of the operation.

Exponent overflow, exponent underflow, or lost sig

nificance cannot occur.

Resulting Condition Code:

o Operands are equal

1 First operand is low

2 First operand is high

3

Program Interruptions:

Operation (if floating-point feature is not in

stalled)

Addressing (CD and CE only)

Significance

Programming Note

Numbers with zero fraction compare equal even when

they differ in sign or characteristic.Halve HER RR (Short Operands)

34

7 8 11 12 15

HDR RR (Long Operands)

24

7 8 11 12 15

The second operand is divided by two, and the

quotient is placed in the first operand location.

In short-precision, the low-order half of the result

register remains unchanged.

The operation shifts the fraction right one bit; the

sign and characteristic are not changed. No normaliza

tion or test for zero fraction takes place.

Condition Code: The code remains unchanged.

Program Interruptions:Operation (if floating-point feature is not in

stalled)

Specification

Programming Note

The halve operation differs from a divide operation

with the number two as divisor in the absence of pre

normalization and postnormalization and in the ab

sence of a zero-fraction test.Multiply MER RR (Short Operands) I 3C R] I R2 0 7 8 11 12 15

ME RX (Short Operands)

7C R]I X

2I B2

7 8 11 12 1516 1920 31

MDR RR (Long Operands)I 2C R] I R2 I 0 7 8 11 12 15

MD RX (Long Operands)I 6C R] I X

2I B2 0 7 8 11 12 1516 1920 31

The normalized product of multiplier (the second op

erand) and multiplicand (the first operand) replaces

the multiplicand.

The multiplication of two floating-point numbers

consists of a characteristic addition and a fraction

multiplication. The sum of the characteristics less 64 is

used as the characteristic of an intermediate product.

The sign of the product is determined by the rules of

algebra.

The product fraction is normalized by prenormaliz

ing the operands and postnormalizing the intermediate

product, if necessary. The intermediate product char

acteristic is reduced by the number of left-shifts. For

long operands, the intermediate product fraction is

truncated before the left-shifting, if any. For short

operands (six-digit fractions), the product fraction has

the full 14 digits of the long format, and the two low

order fraction digits are accordingly always zero.

Exponent overflow occurs if the final product char

acteristic exceeds 127. The operation is terminated,

and a program interruption occurs. The overflow ex

ception does not occur for an intermediate product

characteristic exceeding 127 when the final character

istic is brought within range because of normalization.

Exponent underflow occurs if the final product char-

Floating-Point Arithmetic 47

operand is changed as a result of the operation.

Exponent overflow, exponent underflow, or lost sig

nificance cannot occur.

Resulting Condition Code:

o Operands are equal

1 First operand is low

2 First operand is high

3

Program Interruptions:

Operation (if floating-point feature is not in

stalled)

Addressing (CD and CE only)

Significance

Programming Note

Numbers with zero fraction compare equal even when

they differ in sign or characteristic.

34

7 8 11 12 15

HDR RR (Long Operands)

24

7 8 11 12 15

The second operand is divided by two, and the

quotient is placed in the first operand location.

In short-precision, the low-order half of the result

register remains unchanged.

The operation shifts the fraction right one bit; the

sign and characteristic are not changed. No normaliza

tion or test for zero fraction takes place.

Condition Code: The code remains unchanged.

Program Interruptions:

stalled)

Specification

Programming Note

The halve operation differs from a divide operation

with the number two as divisor in the absence of pre

normalization and postnormalization and in the ab

sence of a zero-fraction test.

ME RX (Short Operands)

7C R]

2

7 8 11 12 1516 1920 31

MDR RR (Long Operands)

MD RX (Long Operands)

2

The normalized product of multiplier (the second op

erand) and multiplicand (the first operand) replaces

the multiplicand.

The multiplication of two floating-point numbers

consists of a characteristic addition and a fraction

multiplication. The sum of the characteristics less 64 is

used as the characteristic of an intermediate product.

The sign of the product is determined by the rules of

algebra.

The product fraction is normalized by prenormaliz

ing the operands and postnormalizing the intermediate

product, if necessary. The intermediate product char

acteristic is reduced by the number of left-shifts. For

long operands, the intermediate product fraction is

truncated before the left-shifting, if any. For short

operands (six-digit fractions), the product fraction has

the full 14 digits of the long format, and the two low

order fraction digits are accordingly always zero.

Exponent overflow occurs if the final product char

acteristic exceeds 127. The operation is terminated,

and a program interruption occurs. The overflow ex

ception does not occur for an intermediate product

characteristic exceeding 127 when the final character

istic is brought within range because of normalization.

Exponent underflow occurs if the final product char-

Floating-Point Arithmetic 47