DOCUMENTATION.txt

{{Lowercase}}
'''dual tape''' is a "two" instruction tape machine. Every cell holds an instruction and a number.

== About ==
{| class="wikitable"
!About
|-
| Author
| Charles McMarrow
|-
| User
| [[User:Ch44d]]
|-
| Conceived
| 8/18/2021
|-
| Birthday
| 10/29/2021
|}

{| class="wikitable"
!Official Interpreter
|-
| '''pip install dual_tape'''
|-
| https://github.com/cmcmarrow/dual_tape
|}

== Instructions ==
{| class="wikitable"
!Name
!Instruction
!Description
|-
| style="vertical-align: top"| <code><nowiki>Next</nowiki></code>
| style="vertical-align: top"| <code><span style="color:red"><nowiki>n</nowiki></span></code>
| style="vertical-align: top"| Increment to the next rule and increment to the next instruction.
|-
| style="vertical-align: top"| <code><nowiki>Execute</nowiki></code>
| style="vertical-align: top"| <code><span style="color:red"><nowiki>x</nowiki></span></code>
| style="vertical-align: top"| Execute the current rule.
|}

== Rules ==
{| class="wikitable"
!Name
!Description
|-
| style="vertical-align: top"| <code><nowiki>Halt</nowiki></code>
| style="vertical-align: top"| Stop the program.
|-
| style="vertical-align: top"| <code><nowiki>Out Number</nowiki></code>
| style="vertical-align: top"| Outputs the number from item_1.
|-
| style="vertical-align: top"| <code><nowiki>Out Character</nowiki></code>
| style="vertical-align: top"| Outputs the number as a UTF-8 character from item_1.
|-
| style="vertical-align: top"| <code><nowiki>In Number</nowiki></code>
| style="vertical-align: top"| Read number from console into item_1. Falls back to 0 if error.
|-
| style="vertical-align: top"| <code><nowiki>In Character</nowiki></code>
| style="vertical-align: top"| Read UTF-8 character from console into item_1. Falls back to "\0" if error.
|-
| style="vertical-align: top"| <code><nowiki>Add</nowiki></code>
| style="vertical-align: top"| item_1 = item_2 + item_1
|-
| style="vertical-align: top"| <code><nowiki>Subtract</nowiki></code>
| style="vertical-align: top"| item_1 = item_2 - item_1
|-
| style="vertical-align: top"| <code><nowiki>Jump</nowiki></code>
| style="vertical-align: top"| pc = current value in memory
|-
| style="vertical-align: top"| <code><nowiki>Jump Dynamic</nowiki></code>
| style="vertical-align: top"| pc = value from memory address in item_1
|-
| style="vertical-align: top"| <code><nowiki>Jump Zero</nowiki></code>
| style="vertical-align: top"| pc = item_1 if item_2 == 0
|-
| style="vertical-align: top"| <code><nowiki>Jump Greater</nowiki></code>
| style="vertical-align: top"| pc = item_1 if item_2 >= 0
|-
| style="vertical-align: top"| <code><nowiki>Read</nowiki></code>
| style="vertical-align: top"| item_2 = item_1; item_1 = current value in memory
|-
| style="vertical-align: top"| <code><nowiki>Read Dynamic</nowiki></code>
| style="vertical-align: top"| item_2 = item_1; item_1 = value from memory address in item_1
|-
| style="vertical-align: top"| <code><nowiki>Read Dynamic Instruction</nowiki></code>
| style="vertical-align: top"| item_2 = item_1; item_1 = value from memory instruction address in item_1
|-
| style="vertical-align: top"| <code><nowiki>Write</nowiki></code>
| style="vertical-align: top"| current location in memory = item_1
|-
| style="vertical-align: top"| <code><nowiki>Write Dynamic</nowiki></code>
| style="vertical-align: top"| value from memory address in item_1 = item_2
|-
| style="vertical-align: top"| <code><nowiki>Write Dynamic Instruction</nowiki></code>
| style="vertical-align: top"| value from memory instruction address in item_1 = item_2 if item_2 is a valid instruction
|}

== Registers ==
{| class="wikitable"
! Register
! Description
|-
| style="vertical-align: top"| <code><span style="color:red"><nowiki>pc</nowiki></span></code>
| Holds the current program counter. At program start pc is set to the label "@". If Label "@" is not present an error will be thrown.
|-
| style="vertical-align: top"| <code><span style="color:red"><nowiki>item_1</nowiki></span></code>
| Set to 0 at program start.
|-
| style="vertical-align: top"| <code><span style="color:red"><nowiki>item_2</nowiki></span></code>
| Set to 0 at program start.
|-
| style="vertical-align: top"| <code><span style="color:red"><nowiki>rule</nowiki></span></code>
| Set to Halt at program start. The Next instruction uses this register to cycle through all the rules in the order listed.
|}

== Memory ==
A single memory cell holds two items, instruction and data. The default instruction value is "n" and the default data value is 0. Memory range is negative infinity to infinity.

== Syntax ==
{| class="wikitable"
!Syntax
|-
| <nowiki><CODE> ::= {(([LABEL] INSTRUCTION [LABEL | NUMBER | CHARACTER | COMMENT] [COMMENT]) | COMMENT | "") NEWLINE}</nowiki>
|-
| <nowiki><LABEL> ::= "@" {Any UTF-8 Character excluding white space}</nowiki>
|-
| <nowiki><INSTRUCTION> ::= "n" | "x"</nowiki>
|-
| <nowiki><COMMENT> ::= "#" {Any UTF-8 Character excluding NEWLINE}</nowiki>
|-
| <nowiki><NEWLINE> ::= "\n"</nowiki>
|-
| <nowiki><CHARACTER> ::= "c" (Normal UTF-8 Character)</nowiki>
|-
| <nowiki><NUMBER> ::= An Integer</nowiki>
|}

== Sister Language ==
[[dual_tape_ez]]

== Programs ==
=== [[truth-machine]] ===
 @ n # Truth Machine
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 x @zero
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 @one_loop n
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 x @one_loop
 @zero n
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 x 0
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=== Hello World ===
 @ n # Hello World
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 x cH
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 x 32
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 x cd
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 x c!
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 x 10
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[[Category:Implemented]]
[[Category:Languages]]
[[Category:Turing complete]]
[[Category:Cell-based]]
[[Category:Self-modifying]]
[[Category:Low-level]]
[[Category:2021]]