Definitions

condition code register

Status register

A status register (also: flag register or condition code register (CCR)) is a collection of flag bits for a processor. A popular example of a status register is the FLAGS register of x86 architecture based microprocessors.

Common status register flags

  • Z — Zero flag. Indicates that the result of a mathematical or logical operation was zero.
  • CCarry flag. Indicates that the result of an operation produced an answer greater than the number of available bits. (This flag may also be set before a mathematical operation as an extra operand to certain instructions, e.g. "add with carry".)
  • X — Extend bit.
  • N (or S) — Negative or Sign flag. Indicates that the result of a mathematical operation is negative. In some processors, the N and S flags have different meanings: the S flag indicates whether a subtraction or addition has taken place, whereas the N flag indicates whether the last operation result is positive or negative.
  • V (or O or W) — Overflow flag. Indicates that the result of an operation has overflowed according to the CPU's word representation, similar to the carry flag but for signed operations.
  • I (or E) — Interrupt enable flag. Interrupts can be enabled or disabled by respectively setting or clearing this flag. Modifying this flag may be restricted to programs executing in supervisor mode.
  • PParity flag. Indicate that the number of bits of the result is odd or even.
  • D (or T) — Debug or Trap flag. Specifies that a special tracing interrupt is generated immediately after each single instruction is executed. This is used to implement program code debuggers.

See also

References

Search another word or see condition code registeron Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature