The Zero Flag is a single bit flag that is a central feature on most conventional CPU architectures (including x86, ARM

ARM

An arm is an upper limb of the body.Arm may also refer to:-Geography:* Arm , a narrow stretch of a larger body of water** Canal arm, a subsidiary branch of a canal or inland waterway** Distributary or arm, a subsidiary branch of a river...

, PDP-11

PDP-11

The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...

, 68000 and numerous others). It is often stored in a dedicated register, typically called status register

Status register

A status register or flag register is a collection of flag bits for a processor. An example is the FLAGS register of the x86 architecture....

 or flag register, along with other flags. The zero flag is typically abbreviated Z or ZF or similar in most documentation and assembly languages.

Along with a carry flag

Carry flag

In computer processors the carry flag is a single bit in a system status register used to indicate when an arithmetic carry or borrow has been generated out of the most significant ALU bit position...

, a sign flag and an overflow flag

Overflow flag

In computer processors, the overflow flag is usually a single bit in a system status register used to indicate when an arithmetic overflow has occurred in an operation, indicating that the signed two's-complement result would not fit in the number of bits used for the operation...

, the zero flag is used to check the result of an arithmetic operation, including bitwise logical instruction

Instruction set

An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...

s. It is set if an arithmetic result is zero, and reset otherwise. This includes results which are not stored, as most traditional instruction sets implement the compare instruction as a subtract where the result is discarded. It is also common that processors have a bitwise AND-instruction that does not store the result.

In most processors, the zero flag is mainly used in conditional branch

Branch (computer science)

A branch is sequence of code in a computer program which is conditionally executed depending on whether the flow of control is altered or not . The term can be used when referring to programs in high level languages as well as program written in machine code or assembly language...

 instructions, which alter control flow on previous instruction results, but there are often other uses as well.

In some instruction sets such as the MIPS architecture

MIPS architecture

MIPS is a reduced instruction set computer instruction set architecture developed by MIPS Technologies . The early MIPS architectures were 32-bit, and later versions were 64-bit...

, a dedicated flag register is not used; jump instructions instead check a register for zero.