The Difference Between Local and Global Variables
When it comes to programming, the concept of a variable plays an important role. While working on a code, there are two types of variables that programmers commonly use, which are local and global variables. Both types have unique characteristics that differentiate one from the other. In this article, we will explain the difference between local and global variables.
Local Variables
A local variable is one that is created inside a function or a block of code. This type of variable is accessible only within that function or block and cannot be accessed from outside of it. The scope of a local variable is limited to the function or block where it was declared.
Local variables are used to store temporary data that is required only within a specific function or block. Once the execution of that function or block is complete, the value of the local variable will be lost. The memory allocation for a local variable is done automatically by the compiler, and once its associated function or block is finished, the memory is automatically freed.
Global Variables
A global variable, on the other hand, is a variable that is defined outside of a function or block of code. This type of variable can be accessed from any part of the program. The scope of a global variable is not limited to a specific function or block, and it can be accessed from any part of the code.
Global variables are used to store data that is required throughout the program. Since global variables are accessible from any part of the code, they are often used to pass data between different parts of the program. A global variable is allocated in memory at the beginning of the program, and remains in memory until the program is terminated.
Key Differences
1. Scope: The scope of a local variable is limited to the function or block where it is declared while the scope of a global variable is not limited to any specific function or block.
2. Availability: The local variable is accessible only within the function or block where it was declared while the global variable can be accessed from any part of the code.
3. Memory Allocation: The memory for a local variable is allocated and freed automatically by the compiler while memory for a global variable is allocated at the beginning of the program and remains in memory until the program ends.
4. Usage: Local variables are used to store data that is required temporarily within a specific function, while global variables are used to store data that is required throughout the program.
In conclusion, both local and global variables have their unique advantages and are used depending on the requirement of the program. Understanding the difference between them will help programmers to use them efficiently to create high-quality code.
Table difference between local and global variable
| Variable Type | Scope | Access |
|---|---|---|
| Local variable | Declared inside a function, available only within the function code block | Can be accessed and modified only within the function code block |
| Global variable | Declared outside a function, available throughout the code | Can be accessed and modified in any part of the code, unless specified otherwise using the ‘let’ or ‘const’ keyword |