Instruction refers to the act or practice of teaching or imparting knowledge or information. It can also refer to a set of directions or orders that someone gives to another person. Instruction is vital for education, as it is the transfer of learning from one person to another. In the context of computing, an instruction is an order given to a computer processor by a computer program. A collection of computer instructions is called an instruction set, which facilitates a variety of tasks for a computer systems central processing unit (CPU) to execute. Instructions can vary in length and can specify special storage areas called registers that may contain data to be used in carrying out an instruction. The principal categories of instructions a computer must have to process information include computing, storage, and input/output instructions.