RCA 301, Programmer'S Reference Manual

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APPENDIX J. GLOSSARY OF TERMS (Continued)
Positional Notation. One of the schemes for representing numbers, characterized by the arrangement in sequence of
digits which are to be interpreted as co-efficients of successive powers of an integer called the base of the
number system.
In the binary number system the successive digits are interpreted as co-efficients of the successive powers of
the base 2, just as in the decimal number system they relate to successive powers of the base 10.
In the ordinary number systems the digits are symbols which stand for zero and for the positive integers smaller
tljan the base.
PRl's. Previous Result Indicators.
PRN. Previous Result Negative Indicator.
PRP. Previous Result Positive Indicator.
PRZ. Previous Result Zero Indicator.
Preamble. A pattern of bits recorded by hardware in front of all blocks as they are written. It is used to synchronize
the reading timing clock when reading and read-after-write commands.
Preselect. The technique of overlapping card movement within the same Retrieval Unit. While one select is in process
another may be readied for extraction. (See Select above.)
Program Control Card. A 3488 card containing information necessary to operate and maintain programs on the 3488.
Program Index. Specifies the Program name and the location of the program within the system.
Program Area Index. Describes the allocated program areas. Contains the file ID and a description of the
program area.
Random Access. Access to storage under conditions in which the next position from which information is obtained,
or to which it is delivered, is in no way dependent on the previous one.
RCA Character. See the RCA 301 Code, Appendix.
Record. A record consists of one or more related items with the amount of information in a record being completely
variable.
Register. A storage device with a specifically assigned function and a given unit capacity. Registers in the computer
in the RCA 301 System are of one, two, or four character capacity.
Relative Address. An address which specifies a location sequentially relative to a group of addresses but not a specific
storage location.
Rewind. Move a tape in a backward direction to BTC.
Routine. A set of instructions arranged in proper sequence to cause a machine to perform a desired operation.
R to L. Right to Left.
RWD. Rewind.
Sector. An addressable unit of information on the Data Disc File. One sector contains 160 characters. Ten sectors
are contained in one track.
Select. (Software usage — see explanations listed below.)
Card Select. The mechanical extraction of a 3488 card from a magazine and placing in on the drum.
Block Select. Placing a specified block under the read/write head while the 3488 card containing that block
is on the drum.
Sign Position. The sign of each operand is indicated by the 2
3
bit of the least significant digit (LSD) of each operand.
When a "one" bit is present in the 2" p osition, the sign is negative, otherwise it is assumed positive.
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