Address Binding and its Types

Address Binding is the mapping of a physical address to a logical address known as a virtual address, it allocates a physical memory region to a logical pointer. In this article, We are going to cover address binding with the help of an example and Its types like compile time, load time, and execution time address binding. Let's discuss one by one.

What is Address Binding?

The mapping of data and computer instructions to actual memory locations is known as address binding. In computer memory, logical and physical addresses are employed. Additionally, the OS handles this aspect of computer memory management on behalf of programs that need memory access. Let's consider the following example given below for better understanding. Consider a program P1 has a set of instructions such that I1, I2, I3, I4, and program counter values are 10, 20, 30, and 40 respectively.

Program P1
I1 --> 10 
I2 --> 20 
I3 --> 30 
I4 --> 40

Program Counter = 10, 20, 30, 40

Why Do We Need Address Binding?

• Memory Management: Address binding is critical for memory management effectively within a machine.
• Symbol Resolution: Address binding resolves symbolic references in a program to real memory addresses. This method permits the linker/loader to attach program modules, libraries, or functions, and execute correctly.
• Code Relocation: Address binding allows code relocation, allowing executable applications to be loaded into memory at unique addresses whenever they run.
• Dynamic Memory Allocation: Address binding helps dynamic memory allocation, allowing packages to request and release memory dynamically at some stage in runtime. Functions used for dynamic memory allocation are malloc() and free() in programming languages.

Types of Address Binding

The mapping of data and computer instructions to actual memory locations is known as address binding. In computer memory, logical and physical addresses are employed. Address Binding is divided into three types as follows:

• Compile-time Address Binding
• Load time Address Binding
• Execution time Address Binding

Compile-Time Address Binding

If the compiler is responsible for performing address binding then it is called compile-time address binding. During the compilation stage of a program, compile-time binding sometimes referred to as static binding, links symbolic addresses with physical memory addresses. Before the program runs, the addresses are found and fixed. For functions and global variables that have a fixed memory location during program execution, this kind of binding is frequently utilized. Compile-time binding has the benefit of being straightforward and effective because the addresses are known ahead of time. Its inability to adjust to runtime changes stems from the addresses staying the same throughout program execution. The compiler requires interaction with an OS memory manager to perform compile-time address binding.

Load Time Address Binding

It will be done after loading the program into memory. This type of address binding will be done by the OS memory manager i.e. loader. The address binding procedure is postponed by load-time binding until the program is loaded into memory to be executed. The linker and loader assign memory addresses to variables and functions during the loading phase by the memory capacity and the functions' needs. External references are resolved by the linker, which also replaces symbolic locations with their actual physical addresses. Compared to compile-time binding, load-time binding offers greater flexibility because the addresses can be changed by particular runtime circumstances. It provides dynamic libraries and lets the application adjust to variations in memory available.

Execution Time or Dynamic Address Binding

It will be postponed even after loading the program into memory. The program will be kept on changing the locations in memory until the time of program execution. During program execution, address binding is handled by runtime binding, sometimes referred to as dynamic binding. More flexibility is possible with this kind of binding since memory addresses can be dynamically allocated and deallocated as needed. In dynamic and object-oriented programming languages, where the memory layout might change while the program is running, runtime binding is frequently employed. When a program uses runtime binding, it resolves symbolic addresses based on the program's present state. This improves the program's flexibility and adaptability by enabling late binding of functions, polymorphism, and dynamic memory allocation.

Noteimplements: The majority of the Operating System practically implement dynamic loading, dynamic linking, and dynamic address binding. For example - Windows, Linux, and Unix are all popular OS.

Conclusion

Operating systems rely on address binding to bridge the gap between the physical memory addresses that the underlying hardware understands and the symbolic addresses that programs use. Address binding in OS allows for effective memory management and smooth communication between hardware and software by associating these addresses at runtime. Compile-time binding, load-time binding, and runtime binding are the three main forms of address binding that have been discussed in this article. Each kind meets various program requirements and runtime situations while providing unique benefits and trade-offs.