In direct addressing mode address of the operand is placed directly in the instruction itself. Suppose in a 32 bit instruction address field of operand occupies 16 bit. So effectively this instruction can address only 2^16 addresses means it cannot fully address the whole address space. This problem is addressed in indirect addressing scheme where address of the operand resides in the memory and address of that location is put into the instruction. In this case address can be in any location of memory. Thus indirect addressing mode has larger address space.