Editing Modula-3 (section)

===Safe vs unsafe===
Some ability is deemed unsafe, where the compiler can no longer guarantee that results will be consistent; for example, when interfacing to the [[C (programming language)|C]] language. The keyword <code>UNSAFE</code> prefixed in front of <code>INTERFACE</code> or <code>MODULE</code>, may be used to tell the compiler to enable certain low level features of the language. For example, an unsafe operation is bypassing the type system using <code>LOOPHOLE</code> to copy the bits of an integer into a floating point <code>REAL</code> number.

An interface that imports an unsafe module must also be unsafe. A safe interface may be exported by an unsafe implementation module. This is the typical use when interfacing to external [[Library (computing)|libraries]], where two interfaces are built: one unsafe, the other safe.