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Cheese with Holes (Emmental) - Developing
Cheese with Holes (Emmental) - Developing
Useful note with basic structure, but still has holes to fill.
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One Instruction Set Computer (OISC)

Author: guiferviz

Created:

Last Modified:

A One Instruction Set Computer (OISC), also known as an Ultimate Reduced Instruction Set Computer (URISC), is a type of computer architecture that uses only a single instruction to perform all operations. Despite having only one instruction, an OISC can still be Turing complete if the single instruction is powerful enough.

Examples:

  1. Subleq (Subtract and Branch if Less than or Equal to Zero):

    • Instruction: subleq A, B, C
    • Operation: Subtract the value at address A from the value at address B, store the result at B, and if the result is less than or equal to zero, jump to address C.
    • Explanation: This instruction can perform arithmetic (through repeated subtraction), conditional branching (with the jump), and memory manipulation (by storing the result).

  2. Move and Branch (MOV):

    • Instruction: mov A, B
    • Operation: Move the value at address A to address B, and then based on the value or some condition, decide whether to branch to another instruction.
    • Explanation: With clever use of memory and conditions, this can simulate other operations and control flow.
> movfuscator is a C
compiler that uses only the mov instruction. There is also a video from the author explaining how he did it.
Yet as it turns out, we can do comparisons using only load and store
instructions. If you store a value into address A and a different value into address B, then examining the contents of address A afterwards will tell you whether A and B are equal.