United States. Department of Defense

“ There shall be an exception handling mechanism for responding to unplanned error situations detected in declarations and statements during execution. The exception situations shall include errors detected by hardware, software errors detected during execution, error situations in built-in operations, and user defined exceptions. Exception identifiers shall have a scope. Exceptions should add to the execution time of programs only if they are raised. ”

“ To the extent that it does not interfere with other requirements, the language shall facilitate the production of translators that are easy to implement and are efficient during translation. There shall be no language restrictions that are not enforceable by translators.
1G. Machine Independence. The design of the language should strive for machine independence. It shall not dictate the characteristics of object machines or operating systems except to the extent that such characteristics are implied by the semantics of control structures and built-in operations. ”

“ Each execution of the constructor operation for an indirect type shall create a distinct element of the type. An operation that distinguishes between different elements, an operation that replaces all of the component values of an element without altering the element's identity, and an operation that produces a new element having the same component values as its argument, shall be automatically defined for each indirect type. ”

“ A reference to an identifier that is not declared in the most local scope shall refer to a program element that is lexically global, rather than to one that is global through the dynamic calling structure.
Functions 7D. Function Declarations. The type of the result for each function must be specified in its declaration and shall be determinable during translation. The results of functions may be of any type. If a result is of a nonindirect array or record type then the number of its components must be determinable by the time of function call. ”

“ An encapsulation may contain declarations of anything (including the data elements and operations-comprising a type) that is definable in programs. The language shall permit multiple explicit instantiations of an encapsulation.
3-5B. Effect of Encapsulation. An encapsulation may be used to inhibit external access to implementation properties of the definition. In particular, it shall be possible to prevent external reference to any declaration within the encapsulation including automatically defined operations such as type conversions and equality. ”

“ It shall be possible to declare constants of any type. Such constants shall include both those whose values-are determined during translation and those whose value cannot be determined until allocation. ”

“ It shall be possible to access a real time clock. There shall be translation time constants to convert between the implementation units and the program units for real time. On any control path, it shall be possible to delay until at least a specified time before continuing execution. A process may have an accessible clock giving the cumulative processing time (i.e., CPU time) for that process. ”

“ Features should be chosen to have a simple and efficient implementation in many object machines, to avoid execution costs for available generality where it is not needed, to maximize the number of safe optimizations available to translators, and to ensure that unused and constant portions of programs will not add to execution costs. ”

“ General Design Criteria General Syntax Types Expressions Constants, Variables, and Scopes Classical Control Structures Functions and Procedures Input-Output, Formating and Configuration Control Parallel Processing Exception Handling Representation and Other Translation Time Facilities Translation and Library Facilities Support for the Language PREFACE The Department of Defense Common High Order Language program was established in 1975 with the goal of establishing a single high order computer programming language appropriate for DoD embedded computer systems. ”

“ The errors detectable during execution shall include exceeding the specified range of an array subscript, exceeding the specified range of a variable, exceeding the implemented range of a variable, attempting to access an uninitialized variable, attempting to access a field of a variant that is not present, requesting a resource (such as stack or heap storage) when an insufficient quantity remains, and failing to satisfy a program specified assertion. ”

“ Several requirements have been restated to remove constraints that were unintended but were implied because the requirement suggested a particular mechanism rather than giving the underlying requirement. The requirements for embedded comments (2I) , unordered enumeration types (3-2B) , associative operator specifications (7D) , dynamic aliasing of array components (10B) , and multiple representations of data (11B) have been deleted because they have been found unnecessary or are not adequately justified. ”

“ A recommended set of translation diagnostic and warning messages shall be included in the language definition.
13B. Standards. There will be a standard definition of the language. Procedures will be established for standards control and for certification that translators meet the standard.
13C. Completeness of Implementations. Translators shall implement the standard definition. Every translator shall be able to process any syntactically correct program. Every feature that is available to the user shall be defined in the standard, in an accessible library, or in the source program. ”

“ Neither the language nor its translators shall impose arbitrary restrictions on language features. For example, they shall not impose restrictions on the number of array dimensions, on the number of identifiers, on the length of identifiers, or on the number of nested parentheses levels.
13G. Software Tools end Application Packages. The language should be designed to work in conjunction with a variety of useful software tools and application support packages. ”

“ These will be developed as early as possible and will include editors, interpreters, diagnostic aids, program analyzers, documentation aids, testing aids, software maintenance tools, optimizers, and application libraries. There will be a consistent user interface for these tools. Where practical software tools and aids will be written in the language. Support for the design, implementation, distribution, and maintenance of translators, software tools and aids, and application libraries will be provided independently of the individual projects that use them. ”

“ Such specifications must include the object machine model, the operating system if present, peripheral equipment, and the device configuration, and may include special hardware options and memory size. The translator will use such specifications when generating object code. [Note that programs that depend on the specific characteristics of the object machine, may be made more portable by enclosing those portions in branches of conditionals on the object machine configuration.] ”