Static storage allocation is a memory management technique used in programming languages where the memory for variables is allocated and fixed at compile-time, rather than being dynamically allocated at run-time. In this approach, the size and location of variables are determined before the program starts running, and the allocated memory remains constant throughout the program’s execution.

 In a programming language that uses static allocation in activation records, (activation record is the contiguous block of storage that manages the information which is needed for the execution of single procedure in a program) , the  implementation of call, return, and halt typically involves managing the call stack and executing function calls and returns. Since static allocation means memory for variables is fixed at compile-time, the focus is on handling the flow of control between functions.

Here’s a high-level implementation of these operations:

Implementation of the call statement

The codes needed to implement static allocation are as follows –

MOV #here +20, callee.static_area            It saves return address  
GOTO callee.code_area It transfers control to the target code for the called Procedure.  
Callee.static_area.  − An address of the activation record.
Callee.code_area.     − An address of the first instruction for called procedure.
#here +20.        − Literal return address which is the address of the instruction following GOTO.

Implementation of return statement

A return from procedure callee is implemented by –
GOTO * callee.static_area
This transfers control to the address saved at the beginning of the activation record.

Implementation of action statement

The instruction ACTION is used to implement an action statement.

Implementation of halt statement

The statement HALT is the final instruction that returns control to the operating system

For example, the array declaration is an example of a static memory allocation and the size of the array must be known beforehand. You cannot change the size of the array once the memory is allocated.  

Here are some of the key benefits of static storage allocation:

Efficient Memory Access:

Static storage allocation provides direct and efficient access to variables because their memory addresses are known at compile-time. There is no need to perform dynamic memory lookups or calculations during run-time, leading to faster memory access and improved program performance.

Deterministic Lifetime:

Variables with static storage duration have a deterministic lifetime that spans the entire program’s execution. They are initialized once before the program starts running and retain their values until the program terminates. This can be advantageous when variables need to maintain their values across function calls or throughout the entire program’s execution.

Simple Memory Management:

Static storage allocation eliminates the need for explicit memory allocation and deallocation calls by the programmer. This simplifies memory management, reducing the chances of memory leaks or memory-related bugs.

Thread Safety in Single-Threaded Environments: In single-threaded programs, static variables can be used without concerns about thread safety, as they are accessible from a single execution thread.

No Runtime Overhead:

Unlike dynamic memory allocation, static storage allocation does not incur any runtime overhead associated with memory allocation and deallocation. The memory is reserved and assigned at compile-time, making it immediately available for use during the program’s execution.

Global Scope:

Global variables, which are typically statically allocated, have global scope and are accessible throughout the entire program. This can be useful when sharing data between different parts of the program.

Optimized Execution Time:

Since the memory layout and variable addresses are determined at compile-time, the compiler can perform optimizations based on this information, potentially leading to faster execution times.

Suitable for Embedded Systems: Static storage allocation is commonly used in embedded systems, where memory resources are limited, and deterministic behaviour is crucial.

Limitations of static storage management –

Despite these benefits, it’s essential to consider the limitations of static storage allocation. One major limitation is that the memory size is fixed at compile-time, and excessive memory usage may lead to stack overflow or insufficient memory for other parts of the program. Additionally, static storage allocation may not be suitable for data structures whose sizes vary dynamically during program execution.

For example, let’s assume you declare an array of size 40 at compile time but at runtime, you need to add only 12 elements into the array.

In this scenario, the reserved memory for the next 28 elements gets wasted. Or, let’s say you declare an array of size 30 at compile-time, but at runtime, you need to add 7 extra elements into the array. In this case, the size of the array cannot be increased.

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