Hazard (computer architecture):

In the computer architecture, a hazard is a possible problem that can occurs in a pipelined processor. It concern to the possibility of erroneous computation when a CPU tries to simultaneously execute multiple instructions which exhibit data dependence. There are typically 3 types of hazards:1) branching hazards 2) structural hazards and  3) data hazards (control hazards).

Instructions in a pipelined processor are executed in various stages, so that at  any given time many instructions are being executed, and instructions cannot be completed in the required order.

A hazard takes place when two or more of these simultaneous (possibly out of order) instructions conflict.

i) Data hazards

a)RAW - Read After Write

b) WAR - Write After Read

c) WAW - Write After Write

ii) Structural hazards

iii) Branch (control) hazards

iv) Eliminating hazards

a)Eliminating data hazards

b) Eliminating branch hazards