IBM 4300 Manual page 139

Programming Notes
1. Examples of the use of EDIT are given in
Appendix A.
2. Editing includes sign and punctuation control,
and the suppression and protection of leading
zeros by replacing them with blanks or
asterisks. It also facilitates programmed
blanking of all-zero fields. Several fields may
be edited in one operation, and numeric
information may be combined with text.
3. As a rule, the source is shorter than the pattern,
because each 4-bit source digit is generally
replaced by an 8-bit byte in the result.
4. The total number of digit selectors and
significance starters in the pattern must equal
the number of source digits to be edited.
I
5.
If
the fill byte is a blank, if no significance
starter appears in the pattern, and if the source
is all zeros, the editing operation blanks the
result field.
Conditions
Previous State
of Significance Source
Pattern Byte Indicator Digit
Digit selector Off
0
1-9
1-9
On
0-9
0-9
Significance starter Off
0
0
1-9
1-9
On 0-9
0-9
Field separator
* **
Message byte Off
**
On
**
Explanation:
6. The resulting condition code indicates whether
or not the last field is all zeros and, if nonzero,
reflects the state of the significance indicator.
The significance indicator reflects the sign of
the source field only if the last source byte
examined contains a sign code in the low-order
digit position. For multiple-field editing
operations, the condition code reflects the sign
and value only of the field following the last
field separator.
7. Significant performance degradation is possible
when the second-operand address of EDIT
designates a location that is less than the length
of the first operand to the left of a 2,048-byte
boundary. This is because the machine may
perform a trial execution of the instruction to
determine if the second operand actually
crosses the boundary.
It
should be noted that
the second operand of EDIT, while normally
shorter than the first operand, can in the
extreme case have the same length as the first.
Results
State of
Significance
Right Four Indicator at
Source Bits End of Digit
Are Plus Code Result Byte Examination
*
Fill byte Off
No Source digit On
Yes Source digit Off
No Source digit On
Yes Source digit
Off
No Fill byte On
Yes Fill byte Off
No Source digit On
Yes Source digit Off
No Source digit On
Yes Source digit Off
**
Fill byte Off
**
Fi 11 byte Off
**
Message byte On
*
No effect on result byte or on new state of significance indicator
**
Not applicable because source is not examined
Summary of EDIT Functions
8-8 IBM 4300 Processors Principles of Operation