What Is Direct Addressing Mode?

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Addressing modes are conventions used in assembly language programming that specify how certain values are read within a given segment of assembly instructions. There are multiple possible modes, but they are based on the two most common: immediate and direct.

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Immediate Addressing Mode

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Immediate addressing mode means that the value for a given instruction in assembly programming is directly specified. This means the value is constant and written immediately and immutably into the instruction.

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Common Format of Immediate Addressing

The following is an example of the format typically found with immediate addressing mode: Operator Target, ValueIn the example format, the value of the number Value is operated on the value stored in Target. Value is a constant value, which does not change no matter what occurs in the set of assembly instructions.

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Direct Addressing Mode

Direct addressing mode means that the value for a given instruction in assembly programming is pointed to by a given value. This means the value is variable, based on what is stored in memory at a given address.

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Common Format of Direct Addressing

The following is an example of the format typically found with direct addressing mode: Operator Target, (Address)In the example format, the value at the memory location of Address is a variable value in memory, which can be written to and read from during the course of a program. The location in memory is directly specified with a number, which will never change over the course of instruction execution.

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More Modes

There are many more addressing modes available, depending on the assembly language being used. These modes include Scaled, Deferred, Memory Deferred, Auto Increment and a variety of other types.

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