unexecutable

Unexecutable is a term used in computing to describe a piece of code or a program that cannot be run or executed by a processor. This can be due to various reasons, including fundamental design flaws, incorrect syntax, or logical errors that prevent the code from being processed by the machine's instruction set. A common cause of unexecutable code is when it contains instructions that the processor does not understand or when the memory addresses it attempts to access are invalid. It is distinct from code that simply contains bugs or errors that lead to crashes or unexpected behavior during execution. Unexecutable code fails at the very first attempt at processing.

In some contexts, the term "unexecutable" might also refer to a security measure. Certain memory regions within a computer's address space are deliberately marked as unexecutable to prevent malicious code from being injected and run. This is a crucial component of modern security architectures, often implemented through hardware-level features like Data Execution Prevention (DEP) or W^X (Write XOR Execute) policies. By preventing code from running in areas that are only meant for data storage, systems can defend against various types of attacks, such as buffer overflows.