C18 also specifies several environmental limits, ensuring consistency and reliability across different implementations. These limits define the minimum capacities that conforming compilers and execution environments must support. Some of the key translation limits specified are:
- Character Set: The implementation should support a character set adequate for writing C programs, including all characters required by the standard library.
- Identifier Lengths: The implementation must support at least 63 significant initial characters for internal identifiers and 31 for external identifiers.
- Nesting Levels: The standard specifies minimum limits for various nesting levels to ensure that even deeply nested code can be compiled correctly. For example, at least 127 nested levels of blocks should be supported, and 63 levels of function declarations and definitions.
- Line Lengths: Compilers must handle source lines that are at least 4095 characters long.
- Preprocessing Tokens: At least 4095 macro identifiers should be supported for any given program.
