Variable Length Arrays (VLAs) in C

A Variable Length Array is an array whose size is not fixed at compile-time, but instead is decided at runtime.

• Stored on the stack (automatic storage). Their size is determined when execution reaches the declaration.
• They must be declared inside a function (block scope) or in a function prototype scope, not globally.
• VLAs were introduced in the C99 standard, some later standards (like C11) made them optional, so not all compilers may support them.

Output

Enter the Size: 5
1 2 3 4 5 

• Unlike fixed-size arrays, VLAs cannot be initialized using {0} in standard C.
• This works only for arrays with compile-time constants size, e.g, int arr[5] ={0};

Note : However, many modern compilers like GCC and Clang allow this as an extension, so they let it compile without error.

Advantages of VLAs

• Makes code more flexible than fixed-size arrays.
• No need to use dynamic memory functions (malloc/free) for temporary arrays.
• Syntax is simple and similar to normal arrays.

Disadvantages of VLAs

• VLAs are stored on the stack, which has limited memory, very large VLAs may cause stack overflow.
• Cannot be used as global or static arrays.
• Not guaranteed to be supported on all compilers (especially in modern standards like C11).