Implied addressing is an addressing mode which does not require the specification of any additional information. Instructions which are used with implied addressing can not be followed by any information like an address or a constant. This omission of any addressing information at all is also called implied addressing.
Instructions in implied addressing mode just take up a single byte in memory. Amongst the 56 officialy documented instructions (see Undocumented opcode) only 25 support implied addressing. These are: BRK, CLC, CLD, CLI, CLV, DEX, DEY, INX, INY, NOP, PHA, PHP, PLA, PLP, RTI, RTS, SEC, SED, SEI, TAX, TAY, TSX, TXA, TXS, and TYA. Named instructions can not be used in any other addressing mode.