ceptions associated with the
Data Exception
A data exception is recognized when:
1. The sign or digit codes of operands in the
decimal-feature instructions or in
2.
coincident rightmost
the rightmost byte of the first operand.
3. The multiplicand in
has an insufficient number of high-order zeros.
Except for EDIT and EDIT AND MARK, the
operation is suppressed when a sign code is invalid,
regardless of whether any other condition causing
the exception exists; otherwise, the operation is ter
minated. However, the contents of the sign position
in the rightmost byte of the result field either remain
unchanged or are set to the preferred sign
contents of the remainder of the result field are un
predictable.
[n the case of EDIT and EDIT AND MARK, an
invalid sign code is not recognized, and the opera
tion is terminated on a data exception.
The instruction-length code is 2 or 3.
Programming Note
When, on a program interruption for data exception,
the program finds that a sign code is invalid, the
operation has been suppressed if the following two
conditions are met:
portion of the result field .
the instruction to be checked for valid sign.
(This condition excludes the first operand of
and EDIT AND MARK.)
An invalid sign code for the rightmost byte of the
result field is not generated when the operation is
terminated. However, an invalid second-operand
sign code is not necessarily preserved when it ap
pears in the numerical portion of the result field.
78 System/370
Fixed-Point-Overflow Exception
A fixed-point-overflow exception is recognized
when a carry occurs out of the high-order bit posi
tion in fixed-point arithmetic operations, or high
order significant bits are lost during the algebraic
left-shift operations.
The interruption may be disallowed in the BC
mode by
code 3 but otherwise ignoring the information placed
outside the register.
The instruction-length code is 1 or 2.
Fixed-Point-Divide Exception
A fixed-point-divide exception is recognized when in
fixed-point division the divisor is zero or the quo
tient exceeds the register size, or when the result of
In the case of division, the operation is sup
pressed. Execution of
completed by ignoring the high-order bits that can
not be placed in the register.
The instruction-length code is 1 or 2.
Decimal-Overflow Exception
A decimal-overflow exception is recognized when
one or more significant high-order digits are lost
because the destination field in a decimal operation
is too small to contain the result.
The interruption may be disallowed in the BC
mode by
The operation is completed by setting condition
code 3 but otherwise ignoring the overflow informa
tion.
The instruction-length code is 2 or 3.
Decimal-Divide Exception
A decimal-divide exception is recognized when in
decimal division the divisor is zero or the quotient
exceeds the specified data field size.
The operation is suppressed .
The instruction-length code is 2 or 3.
Exponent-Overflow Exception
An exponent-overflow exception is recognized when
the result characteristic in floating-point addition,
subtraction, multiplication, or division exceeds 127
and the result fraction is not zero.
The operation is completed. The fraction is nor
malized, and the sign and fraction of the result re
main correct. The result characteristic is made 128
smaller than the correct characteristic.
The instruction-length code is 1 or 2.