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XOR
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<code>XOR</code> performs a bitwise Exclusive-OR on <code>arg1</code> with <code>arg2</code> and stores the result in <code>arg1</code>. That is, only the bits different between <code>arg1</code> and <code>arg2</code> become 1 in the result; all other bits are set to 0. | <code>XOR</code> performs a bitwise Exclusive-OR on <code>arg1</code> with <code>arg2</code> and stores the result in <code>arg1</code>. That is, only the bits different between <code>arg1</code> and <code>arg2</code> become 1 in the result; all other bits are set to 0. | ||
| + | |||
| + | {| class="wikitable" | ||
| + | |+ Truth table for | ||
| + | |+ Y(A, B) = A XOR B | ||
| + | |- | ||
| + | ! Input A !! Input B !! Output Y | ||
| + | |- | ||
| + | | 0 || 0 || 0 | ||
| + | |- | ||
| + | | 0 || 1 || 1 | ||
| + | |- | ||
| + | | 1 || 0 || 1 | ||
| + | |- | ||
| + | | 1 || 1 || 0 | ||
| + | |} | ||
===Example=== | ===Example=== | ||
Latest revision as of 20:11, 13 July 2012
XOR (Exclusive OR) is one of the opcodes in the DCPU-16 specification. It represents a bitwise Exclusive-OR operation.
Contents |
Usage
XOR arg1, arg2
XOR performs a bitwise Exclusive-OR on arg1 with arg2 and stores the result in arg1. That is, only the bits different between arg1 and arg2 become 1 in the result; all other bits are set to 0.
| Input A | Input B | Output Y |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
Example
SET A, 3 ; 0b0011 XOR A, 5 ; 0b0101 ; A is now 0b0110, or 6
In the above program, each bit of each argument to XOR is compared to each other. Starting from the rightmost, least significant bit:
- 1 equals 1, so the LSB of A is set to 0
- 1 is not equal to 0, so the next bit of A is set to 1
- 0 is not equal to 1, so the next bit of A is set to 1
- 0 is not equal to 0, so the next bit of A is set to 0
- Same for the high 12 bits of the arguments - all are 0, so the high 12 bits of A are set to 0.
Signing dependence
XOR works correctly with both signed and unsigned numbers.
Processing
In binary machine code, this Basic opcode's five-bit representation is: 0b0 1100 (0x0c)
The instruction has a takes one cycle to execute, plus any additional cycles necessary to evaluate the arguments.
References
- DCPU-16 specification v1.1 (Copyright 2012 Mojang)
- DCPU-16 specification v1.7 (Copyright 2012 Mojang)
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