RCA 301 Programmer's Reference Manual page 45

THE RCA 3 0 1 I NSTRUCTIONS
INTRODUCTION
The RCA 301 Computer operates under the direction of two-address instructions. For descriptive purposes,
these instructions may be classified into four general categories: (1) Input/Output, (2) Data Handling, (3) Arithmetic
and (4) Decision and Control.
Input/Output Instructions
These instructions enable the Computer to communicate with the peripheral devices. They perform the functions
of positioning or searching tapes or disc files, bringing data from an input medium into the computer or sending
data from the computer to an output medium.
In the group, certain operations can be executed in the Simultaneous Mode as well as in the Normal Mode, so
that operational time for these instructions can overlap that of other instructions. In addition, several instructions
can be executed in the Record File Mode.
Rewind to BTC, Band Select and Track Select instructions as well as the paper advance function are initiated
by the Computer, but once underway, operate completely independent of the Computer. Any number of tapes may be
rewinding while three instructions (unrelated to the rewinding tapes) are being simultaneously executed.
Data Handling Instructions
These are non-arithmetic instructions for manipulation of data stored in the High-Speed Memory. The instructions
included in this group permit operational control by symbol, address, or count. The major data handling functions
operate from right to left or left to right according to the specific instruction involved.
Arithmetic Instructions
Of the instructions in this group, two are decimal, and three are used to alter the bit configuration of an operand
through the use of logical operations.
The decimal instructions operate in accordance with algebraic rules and are designed to handle operands of
equal length.
Three instructions, Logical "OR", Logical "AND" and Exclusive "OR" constitute what may be considered
as a separate arithmetic category. They are used to alter the bit configuration of an operand by the employment of
a second operand to "mask-out" or to insert "1" bits.
The Previous Result Indicators (PRI's) preserve the sign of the result of an arithmetic instruction for reference
by a subsequent decision instruction.
Decision and Control Instructions
These instructions influence the sequence of operation. Three instructions enable the programmer to address
registers directly and one instruction is conditional; that is, it chooses a path according to selected conditions.
One instruction stops the Computer operation. The "Repeat" instruction enables the Computer to execute the same
instruction a designated number of times. The Compare instruction enables the Computer to determine the relative
magnitude of two operands of equal length.
IV — GENERAL DESCRIPTION
IV-1