Redcode

Redcode is a simple, assembly-like programming language used in Core War, a competitive game where programs called warriors battle for control of a fixed-size, circular memory array known as the core. Each warrior’s Redcode program is loaded into the core and executes concurrently with others. The objective is to outlast opponents by overwriting rival code, avoiding being overwritten, or triggering faults that terminate rival processes. The last surviving warrior is declared the winner.

Redcode programs consist of a sequence of instructions with an opcode and operands arranged in A- and B-fields. When executed, instructions may use different addressing modes, such as immediate, direct, or indirect forms, depending on the dialect. Common opcodes include MOV (move data), ADD and SUB (arithmetic), DAT (data and often a termination signal), SPL (spawn a new process), and conditional jumps like JMZ (jump if zero) and JMN (jump if not). The core is circular, so memory references wrap around. Executing a DAT instruction typically terminates the current process, while SPL creates additional processes that run concurrently. Redcode programs may be self-modifying in some dialects, adding strategic complexity.

Standards and dialects: Redcode’s rules have evolved through International Core War Society (ICWS) standards. The most influential early version is ICWS'86, with later variants and extensions that introduced additional instructions and addressing options. Different simulators implement varying subsets of dialects, so code compatibility is dialect-dependent.

Implementation and community: Redcode is supported by several Core War simulators, such as MARS (Memory Array Redcode Simulator) and pMARS (a Java version), along with online tools and annual tournaments. The community uses Redcode to study algorithm design, optimization, and competitive strategy within a well-defined, low-level programming environment.