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--- en:multiasm:cs:chapter_3_10 [2025/01/08 07:27] – [Data addressing] ktokarz
+++ en:multiasm:cs:chapter_3_10 [2025/01/09 08:19] (current) – [Program control flow destination addressing] ktokarz
@@ Line 74: / Line 74: @@
-===== Program flow destination addressing =====
+===== Program control flow destination addressing =====
-Addressing the destination of the program flow change is the operand of jump, branch or function call instructions. In structural or object-oriented high-level languages jump instructions should be avoided, they are rather common in assembler programming. Our examples will use hypothetic //jump// instruction with a single operand - the destination address.
+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//:
@@ Line 82: / Line 82: @@
  jump destin
 </code>
+<figure jumpdirect>
+{{ :en:multiasm:cs:jump_direct.png?600 |Illustration of addressing in direct jump}}
+<caption>Illustration of addressing in direct jump</caption>
+</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//:
@@ Line 87: / Line 92: @@
  jump [R0]
 </code>
+<figure jumpindirect>
+{{ :en:multiasm:cs:jump_indirect.png?600 |Illustration of addressing in indirect jump}}
+<caption>Illustration of addressing in indirect jump</caption>
+</figure>
 ===== 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".
+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>
+{{ :en:multiasm:cs:addressing_absolute.png?600 |Illustration of absolute addressing of the variable}}
+<caption>Illustration of absolute addressing of the variable</caption>
+</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 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.
+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}}.
+<figure addrrelative>
+{{ :en:multiasm:cs:addressing_relative.png?600 |Illustration of IP relative addressing of the variable}}
+<caption>Illustration of IP relative addressing of the variable</caption>
+</figure>
 Relative addressing is also implemented in many jump, branch or loop instructions.

en/multiasm/cs/chapter_3_10.1736321261.txt.gz · Last modified: 2025/01/08 07:27 by ktokarz