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--- en:multiasm:cs:chapter_3_10 [2025/12/10 10:39] – [Data addressing] ktokarz
+++ en:multiasm:cs:chapter_3_10 [2025/12/10 13:22] (current) – [Absolute and Relative addressing] ktokarz
@@ Line 50: / Line 50: @@
 </figure>
-**Variations of indirect addressing**. The indirect addressing mode can have many variations where the final address doesn't have to be the content of a single register, but rather the sum of a constant value with one or more registers. Some variants implement automatic incrementation (similar to the "++" operator) or decrementation ("--") of the index register before or after instruction execution to make processing the tables faster. For example, accessing elements of the table where the base address of the table is named //data_table// and the register //R0// holds the index of the byte which we want to copy from a table to //R1// could look like this:
+**Variations of indirect addressing**. The indirect addressing mode can have many variations where the final address doesn't have to be the content of a single register, but rather the sum of a constant value with one or more registers. Some variants implement automatic incrementation (similar to the "++" operator) or decrementation ("- -") of the index register before or after instruction execution to make processing the tables faster. For example, accessing elements of the table where the base address of the table is named //data_table// and the register //R0// holds the index of the byte which we want to copy from a table to //R1// could look like this:
 <code>
  copy R1, table[R0]
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 The operand of jump, branch, or function call instructions addresses the destination of the program flow control. The result of these instructions is the change of the Instruction Pointer content. Jump instructions should be avoided in structural or object-oriented high-level languages, but they are rather common in assembler programming. Our examples will use the hypothetic //jump// instruction with a single operand—the destination address.
-**Direct addressing** of the destination is similar to direct data addressing. It specifies the destination address as the constant value, usually represented by the name. In assembler, we define the names of the addresses in code as //labels//. In the following example, the code will jump to the label named //destin//:
+**Direct addressing** of the destination is similar to direct data addressing. It specifies the destination address as the constant value, usually represented by a name. In assembler, we define the names of the addresses in code as //labels//. In the following example, the code will jump to the label named //destin//:
 <code>
  jump destin
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 </figure>
-**Indirect addressing** of the destination uses the content of the register as the address where the program will jump. In the following example, the processor will jump to the destination address which is stored in //R0//:
+**Indirect addressing** of the destination uses the content of the register as the address where the program will jump. In the following example, the processor will jump to the destination address, which is stored in //R0//:
 <code>
  jump [R0]
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 ===== Absolute and Relative addressing =====
-In all previous examples, the addresses were specified as the values which represent the **absolute** memory location. The resulting address (even calculated as the sum of some values) was the memory location counted from the beginning of the memory - address "0". It is presented in Fig{{ref>addrabsolute}}.
+In all previous examples, the addresses were specified as the values which represent the **absolute** memory location. The resulting address (even calculated as the sum of some values) was the memory location counted from the beginning of the memory, address "0". It is presented in Fig{{ref>addrabsolute}}.
 <figure addrabsolute>
@@ Line 107: / Line 107: @@
 </figure>
-Absolute addressing is simple and doesn't require any additional calculations by the processor. It is often used in embedded systems, where the software is installed and configured by the designer and the location of programs does not change.
+Absolute addressing is simple and doesn't require any additional calculations by the processor. It is often used in embedded systems, where the software is installed and configured by the designer, and the location of programs does not change.
-Absolute addressing is very hard to use in general-purpose operating systems like Linux or Windows where the user can start a variety of different programs, and their placement in the memory differs every time they're loaded and executed. Much more useful is the **relative addressing** where operands are specified as differences from memory location and some known value which can be easily modified and accessed. Often the operands are provided relative to the Instruction Pointer which allows the program to be loaded at any address in the address space, but the distance between the currently executed instruction and the location of the data it wants to reach is always the same. This is the default addressing mode in the Windows operating system working on x64 machines. It is illustrated in Fig{{ref>addrrelative}}.
+Absolute addressing is very hard to use in general-purpose operating systems like Linux or Windows, where the user can start a variety of different programs, and their placement in the memory differs every time they're loaded and executed. Much more useful is the **relative addressing** where operands are specified as differences from a memory location and some known value, which can be easily modified and accessed. Often, the operands are provided relative to the Instruction Pointer, which allows the program to be loaded at any address in the address space, but the distance between the currently executed instruction and the location of the data it wants to reach is always the same. This is the default addressing mode in the Windows operating system, working on x64 machines. It is illustrated in Fig{{ref>addrrelative}}.
 <figure addrrelative>

en/multiasm/cs/chapter_3_10.1765363194.txt.gz · Last modified: 2025/12/10 10:39 by ktokarz