Statusregister

The Statusregister, also known as the flags register or condition code register, is a special-purpose register in a central processing unit (CPU) that stores status information about the result of an arithmetic or logical operation. It typically consists of a number of individual bits, each representing a specific condition.

Commonly found status bits include the Zero flag (Z), which is set if the result of an operation is zero. The Carry flag (C) is set if an arithmetic operation resulted in a carry-out from the most significant bit, or a borrow for subtraction. The Sign flag (S) or Negative flag (N) is set if the result of an operation is negative, usually indicated by the most significant bit being 1. The Overflow flag (V) is set if the result of a signed arithmetic operation is too large to be represented in the destination operand.

These flags are crucial for controlling program flow. Conditional branch instructions in a program can test the state of these flags to decide whether to execute a particular block of code. For instance, a program might check the Zero flag after a subtraction to see if two values were equal, or check the Carry flag after an addition to detect if the sum exceeded the capacity of the register. This allows for dynamic decision-making within software based on the outcomes of computations. The exact set of flags and their behavior can vary between different CPU architectures.