Direct Addressing and Immediate Addressing mode - computer architecture:
It is the simplest form of addressing. Here, the operand is itself given in the instruction. This mode is used to define constant or set primary values of variables. The benefit of this mode is that no memory reference rather than instruction fetch is needed to obtain operand. The disadvantage of it is that the size of the number is restricted to the size of the address field, in which most of the instruction sets is small compared to word length.
Effective address of the operand is given in the address field of the instruction in the case of direct addressing mode. It need one memory reference to read the operand from the given location and provides only a restricted address space. Length of the address field is typically less than the word length.
For Example: Move P, Ro, Add Q, Ro P and Q are the address of operand. Indirect