The document discusses addressing modes in computers. It defines addressing modes as the different ways of specifying the location of an operand in an instruction. It then describes 10 common addressing modes: implied, immediate, register, register indirect, autoincrement/autodecrement, direct, indirect, relative, indexed, and base register. Each mode is explained with an example to illustrate how the effective address is calculated. Addressing modes provide versatility for programming by enabling features like pointers, loop counters, data indexing, and program relocation while reducing the number of bits needed in instruction addresses.