# 360 Assembly/360 Instructions/DR

**DR** - Divide by Register - Opcode 1D

## Format[edit]

- DR 2,7

The specific syntax is

- DR
*target register*,*source register*.

RR Instruction (2 bytes) | ||||||

Byte 1 | Byte 2 | |||||

target register |
source register |
|||||

(8 bits) Opcode 1D |
(4 bits)0..F |
(4 bits)0..F |

- The first argument is a one with lesser number of pair of
*target registers*which value is affected by the instruction. - The second argument is the source value register.

## Availability[edit]

The DR instruction is available on all models of the 360, 370 and z/System.

## Operation[edit]

The DR instruction divides the dividend - 64-bit signed value stored in pair of registers T and T+1, where T is target register number (T shall contain most significant part and T+1 shall contain least significant part), by the divisor - 32-bit signed value in the source register. The target register number T shall be even. The instruction places quotient to register T and remainder to register T+1, both as 32-bit signed values.

The divisor shall not be zero. The quotient shall fit into limits of 32-bit signed value (-2147483648 till 2147483647).

The DR instruction performs so-called T-division when quotient is truncated to zero; the remainder sign is equal to the dividend sign, if both values are not equal to 0; in other words, (remainder * dividend >= 0).

The Condition Code field in the Program Status Word is not changed.

## Exceptions and Faults[edit]

- If an odd register number is specified as the target register, operation exception occurs.
- If the divisor is zero, operation exception occurs.
- If signed integer overflow is detected and the bit 36 in PSW is set, operation exception occurs.

## Example[edit]

Consider that register 4 contains 0, 5 - 13 and 11 - 4. The instruction "DR 4,11" will divide the contents of register 13 by 4, place the quotient (equals to 3) in register 4 and place the remainder (equals to 1) in register 5.

## Related instructions[edit]

- To divide by word value from memory, see D.
- To multiply by word value from register, see MR.
- To subtract word value from register, see SR.
- To add value and set condition codes according to unsigned arithmetic, or add not most significant part of multi-word integer value, see AL or ALR.
- To divide floating-point values, see DER, DDR, DE or DD.

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