Why addressing modes

The content of the instruction code, represents the starting address of the array and the value of the index register, and the index value of the current element.

By incrementing or decrementing index register different element of the array can be accessed. The effective address of the operand is the contents of a register or main memory location, location whose address appears in the instruction. Indirection is noted by placing the name of the register or the memory address given in the instruction in parentheses. The register or memory location that contains the address of the operand is a pointer.

When an execution takes place in such mode, instruction may be told to go to a specific address. Once it's there, instead of finding an operand, it finds an address where the operand is located. Two memory accesses are required in order to obtain the value of the operand fetch operand address and fetch operand value. Example: SPIM - simulating pointers and indirect register addressing. The address of the operand is embedded in the instruction code.

An instruction cycle, also known as fetch-decode-execute cycle is the basic operational process of a computer. This process is repeated continuously by CPU from boot up to shut down of computer.

The instruction is fetched from memory address that is stored in PC Program Counter and stored in the instruction register IR. At the end of the fetch operation, PC is incremented by 1 and it then points to the next instruction to be executed. If the instruction has an indirect address, the effective address is read from the memory. Otherwise operands are directly read in case of immediate operand instruction. The Control Unit passes the information in the form of control signals to the functional unit of CPU.

The result generated is stored in main memory or sent to an output device. The cycle is then repeated by fetching the next instruction. Thus in this way the instruction cycle is repeated continuously.

Learn Core Java. Java Examples Java 8 Java 11 Java HTML 5 Interactive. CSS Interactive. C Language. Computer Organization and Architecture. Addressing Modes- The different ways of specifying the location of an operand in an instruction are called as addressing modes. Types of Addressing Modes- In computer architecture, there are following types of addressing modes-. Addressing Modes Types of Addressing Modes.

In computer architecture, Addressing Modes specify the location of an operand. Akshay Singhal. Publisher Name.