Explain unsafe Rust and when it is necessary to use unsafe blocks.

Unsafe Rust capabilities and usage: • Dereference raw pointers • Call unsafe functions or methods • Access or modify mutable static variables • Implement unsafe traits • Access fields of unions When unsafe is necessary: • FFI (Foreign Function Interface) • Low-level system programming • Performance-critical optimizations • Implementing safe abstractions • Hardware interaction • Custom allocators Safety rules still apply: • Memory safety is your responsibility • Data race prevention • Proper initialization • Lifetime management Example: // Safe wrapper around unsafe operations fn split_at_mut(slice: &mut [i32], mid: usize) -> (&mut [i32], &mut [i32]) { let len = slice.len(); let ptr = slice.as_mut_ptr(); assert!(mid <= len); unsafe { ( std::slice::from_raw_parts_mut(ptr, mid), std::slice::from_raw_parts_mut(ptr.add(mid), len - mid), ) } } // FFI example extern "C" { fn abs(input: i32) -> i32; } fn main() { unsafe { println!("Absolute value of -3: {}", abs(-3)); } }