An emulator (30) allows subject code (10) written for a subject processor (12) having subject processor registers (14) and condition code flags (16) to run in a non-compatible computing environment (2). The emulator (30) identifies and records parameters of instructions in the subject code (10) that affect status of the subject condition code flags (16). Then, when an instruction in the subject code (10) is encountered, such as a branch or jump, that uses the flag status to make a decision, the flag status is resolved from the recorded instruction parameters. Advantageously, emulation overhead is substantially reduced.