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This file contains an alphabetical listing of Ada-related terms and their meanings. (Ada IC point of contact: Gil Austin) ********************************************************************* Ada* GLOSSARY ********************************************************************* Access type An access type is used to dynamically create objects during execution. Keyword: access. Access value An access value provides the location of an object which has been created by an allocator. Keyword: access. Accuracy constraint An accuracy constraint specifies the relative or absolute error bound of values of a real type. Keywords: delta, digits. Ada* The new High Order Language developed under the sponsorship of the United States Department of Defense (DoD) to obtain the benefits of language commonality across a wide variety of computer systems. Ada has been designated by the DoD as the official language for all future embedded computer application programs. Ada Compiler An integrated set of tests, procedures, Validation Capability software tools, and documentation (ACVC) developed by SofTech, Inc. for conduct- ing validation tests of Ada compilers. The ACVC will be used by the AVO (Ada Validation Organization) to perform formal Ada compiler validation tests. Ada Integrated The Ada language implementation system, Environment (AIE) being developed by Intermetrics, Inc. under contract to the U.S. Air Force, to enable the development of programs written in the Ada language for military computer systems. Ada Language The Ada language implementation system, System (ALS) being developed by SofTech, Inc. under contract to the U.S. Army, that will enable programmers to write programs in the Ada language for execution on advanced, embedded military target computer systems. The ALS represents the first full Ada Programming Support Environment to be supplied to the DoD. Ada Joint Program The office of the DoD responsible for Office the encouragement and control of the (AJPO) development of the Ada language and its implementation in DoD computer systems. Ada Programming A full Ada programming environment Support Environment that enables programmers to write (APSE) programs in the Ada language that can be executed on a wide variety of target computers. The Ada Language System is a friendly, efficient, flexible, easy-to-use programming environment. Ada Validation The component of the AJPO Organization responsible for conducting (AVO) formal Ada compiler validation tests and to encourage the correct implementation of the Ada language. Aggregate An aggregate is a written form denoting a composite value. An array aggregate denotes a value of an array type; a record aggregate denotes a value of a record type. The components of an aggregate may be specified using either positional or named association. Allocator An allocator creates a new object of an access type, and returns an access value designating the location of a created object. Ancestor An ancestor compilation unit of a compilation unit compilation unit currently being compiled is a member of the following set: a. A unit mentioned in a WITH clause of the compilation unit currently being compiled; b. An outer textually-nested unit containing the unit currently being compiled, if that unit is a subunit; c. The specification part of a subprogram or package body currently being compiled; d. One of the units mentioned in a WITH clause of the ancestor compilation undefined in parts (b) and (c) above; and e. Package STANDARD. In short, it is any compilation unit which is made visible to a compilation unit currently being compiled, not including the unit currently being compiled itself. Attribute An attribute is a predefined character- istic. Body A body is a program unit defining the executable portion or implementation of a subprogram, package, or task. Body stub A body stub is a replacement for a body that is compiled separately. Code Generator The component of a compiler back end that generates the machine language for a specified target computer. Typically, a separate code generator is required for each type of target computer. Collection A collection is the entire set of allocated objects of an access type. Compilation unit A compilation unit is a program unit which can be compiled independently from any other text. It is preceded by a specifi- cation naming other compilation units on which it may depend. A compilation unit may be the specification or the body of a subprogram, task, or package. Compiler A compiler is a computer program that can translate source programs written in a High Order Language, such as Ada, into machine language programs that can be executed on specified target computers. Compiler Back End The portion of the compiler that contains the components which depend on the character- istics of the target computer, and therefore must be designed specifically for each target computer. Compiler Front End See MI (Machine Independent Portion) Complete program A program with no unresolved external references is a complete program. Component A component denotes a part of a composite object. An indexed component is a name containing expressions denoting indices, and names a component in an array or an entry in an entry family. A selected component is the identifier of the compon- ent, prefixed by the name of the entity of which it is a component. Composite type An object of a composite type comprises several components. An array type is a composite type, all of whose components are of the same type and subtype; the individual components are selected by their indices. A record type is a composite type whose components may be of different types; the individual components are selected by their identi- fiers. Keywords: Array, record. Composite value The values that make up the components of a composite type. Constraint A constraint is a restriction on the set of possible values of a type. A range constraint specifies lower and upper bounds of the values of a scalar type. An index constraint specifies lower and upper bounds of an array index. A discriminant constraint specifies particular values of the discriminants of a record or private type. Keyword: range. Context A context specification defines specification additional compilation units upon which a following compilation unit depends. Cross Compiler A compiler that enables a computer system to translate a program in one computer language, normally a High Order Language, into a machine language for a different computer system. (Cross compilers are frequently simply called compilers.) Declarative A declarative part is a sequence of part declarations and related information such as subprogram bodies and represen- tation specifications that apply over a region of a program text. Delimiter A separator such as a comma, semi- colon, parentheses, or a colon is called a delimiter. Derived type A derived type is a type whose operations and values are taken from those of an existing type. Keywords: new, subtype. Discrete type The discrete types are the enumera- tion and integer types. A discrete type has an ordered set of distinct values. Discrete types may be used for indexing and iteration, and for choices in case statements and record variants. Discriminant A discriminant is a specially designated component of a record which allows the record to take on various sizes and/or shapes. The variations of the record may depend on the value of the discriminant. Discriminant A discriminant constraint is a constraint restriction on the possible values of the discriminant in a record. DoD The United States Department of Defense. Elaboration Elaboration is the process of assign- ing memory to a declaration. During elaboration, this memory may be initial- ized. Embedded Computer A computer that is included within and functions as an integral part of an operating for processing system or equipment. Embedded computers are typically small, special-purpose machines dedicated to specific operations or functions. Examples are computers in indus- trial robots, navigation systems, and process control equipment. Entity Anything that has a name is an Ada entity; objects, types, values and program units are all entities. Entry The points in a task which communicate with other tasks are entry points. These points have names and may have parameters. In a task, an entry is called just as a subprogram is called. Keyword: entry. Enumeration type An enumeration type has discrete values which are specified in the declaration of the type. These values can be identi- fiers, integers, or characters. Exception An exception is an event that causes the termination of normal program execu- tion. It is expected that an exception is the result of a software or hardware error. Users can define and cause excep- tions to occur that are meaningful to their application. Keywords: exception, raise. Exception An exception handler is that part of a handler program that will be executed when an exception occurs. If no exception handler is provided and an exception occurs, the program will be abnormally terminated. Expression Anything that has a value is an expression. The term is mostly applied to formulas that have a numeric or logical value. Generic program A generic program unit is a subprogram unit which can process parameters of more than one type. The classes of parameters that are acceptable to the subprogram are specified in a generic clause. Before using a generic program unit the types that it is to process are specified during generic instantiation. Keyword: generic. HOL (High Order A programming language that enables a Language) programmer to write in an English-like readable form rather than in complex mathematical machine language. Ada, COBOL, and Fortran are examples of high order languages. Host Computer A computer system on which a programming environment is installed to enable the efficient development of programs to be executed on specified target computers. Host computers are typically large, flexible, multi-programming computer Incomplete program A program which has some unresolved external references is incomplete. Index constraint An index constraint specifies the lower and upper bounds of an array index. Indexed component An indexed component names a component in an array or an entry in a family of task entries. Instantiation Causing a generic program unit to be created for the specified parameter types. Keyword: new. Introduce A declaration introduces an identifier. KAPSE Interface A team of military and DoD-Contractor Team (KIT) personnel, organized by the AJPO and operating under the cognizance of the Naval Ocean Systems Center, established to identify, examine, and set standardization policies for KAPSE interfaces that will promote portability of software and data between Ada programming support environments. Kernel Ada A core group of computer software programs Programming that provides basic functions in support of Support Environment the rest of the Ada programming support (KAPSE) environment, and permits the transfer of the support environment to different host computers without modification. KITIA (KAPSE The industry/academia counterpart of the Interface Team KIT. Industry/Academia) Lexical unit A lexical unit is an identifier, number, character literal, string, delimiter, or comment. Literal A literal states the value for a type. Examples of literals are numbers, enum- eration values, characters or strings. Machine Language The mathematical language used within a computer system. Each type of computer system uses its own, unique machine language. Main subprogram The subprogram which initially executes. Minimal Ada A minimal group of computer software Programming Support programs sufficient to enable programmers to Environment (MAPSE) develop programs written in the Ada language. (When additional programs are added to a MAPSE it becomes an APSE, i.e., a full Ada Program- ming Support Environment.) MI (Machine The portion of the compiler that contains Independent the components which are independent of Portion) the characteristics of the target computers and can be used in common for many target computers. Sometimes called "Compiler Front End". Model number A model number is an exactly representable value of a floating point data type. Arithmetic operations on floating point numbers are defined in terms of operations on model numbers. These operations will be the same on all implementations of Ada. Object An object is a variable or constant. An object can stand for any type of data - scalar, composite, or access. Object Program The output program in machine language produced by a compiler when a source program is supplied as the input. See Source Program. Off-Line Pertains to operations in which the computer is not in direct, concurrent control of the devices or equipment that may receive its output. Normally, additional human intervention is required achieve a desired outcome. Contrast with On-line. On-Line Pertains to operations in which the computer is in direct, concurrent control of the devices or equipment that are receiving its output. Contrast with off- line. Operating System An organized collection of programs and procedures for operating a computer. These procedures will normally perform functions such as scheduling, initiating, and supervis- ing the execution of programs; allocating the facilities of the computer; and coordinat- ing communications between the human operator and the computer system. Overloading Overloading allows operators, identifiers, and literals to have more than one meaning or function. An overloaded operator is one which a user has defined to have special meaning depending on the types which it receives. An overloaded sub- program identifier allows the definition of several subprograms with the same name. The one chosen to execute is the one whose parameters match the invocation. An overloaded enumeration literal is the one that appears in more than one definition of an enumeration type. Ada uses type information to select the correct literal. Package A package is a separately compilable program unit that should contain related data types, data objects, and subprograms that operate on objects with the defined data type. The visible part contains names that can be used external to the package. The private part of the package contains internal data that complete the package specification but are hidden from the user. The body of a package contains the implementations of subprograms which have been specified in the visible part of the package. Other compilation units may use the names introduced in the package by listing the package name in a use clause. Keywords: package, use. Parameter Subprograms, task entries, and generic programs have parameters. A formal parameter is a parameter that defines the parameter in the compilation of the subprogram, task or generic program. An actual parameter is the name of the identifier which is used in a subprogram or task invocation or in a generic instan- tiation. The mode of the parameter speci- fies whether the parameter is used for input, output or input and output to a program. A positional parameter is an actual parameter whose association with a formal parameter is a result of its position in the invocation. A named parameter is an actual parameter whose association with a formal parameter is handled by naming the corresponding formal parameter. PDL An English-like artificial language, (Programming sometimes called pseudo-code, used in Design Language) documenting design logic in software system design. The PDL used in the design of the Ada Language System uses constructs similar to those in the Ada language thereby facilitating the transition to final design. Pragma A pragma instructs the compiler to perform some action such as compiler optimization. Keyword: pragma. Private type A private type is a type which a user may use without knowing its internal data structure. A private type is known by its discriminants and by the set of operations that are defined for it. A private type and operations are defined in the visible part of a package. Assign- ment and inequality are defined for private types unless the private type is also limited. Keywords: private, limited. Program A program is a collection of one or more compilation units which have all been compiled relative to each other. One of the subprograms will be designated to be the main subprogram. Programming An integrated group of computer software Environment programs that provide a wide variety of programming services such as program development and maintenance functions, project control functions, configuration management, and project documentation. Program library The compilation units which make up a program belong to a program library. A program library has a name which is specified in a with clause at the start of compilation. Keyword: with. Qualified A qualified expression further specifies expression an identifier by adding the name of the type or subtype to the name. Occasionally it is necessary to qualify expressions with their type in order to remove ambigu- ities caused by overloading. Range A range is a contiguous set of values of a scalar type. A range is specified by giving the lower and upper bounds for the values. Keyword: range. Range constraint A range constraint specifies the lower and upper bounds of the values of a scalar type. Keyword: range. Real-Time Pertains to fast-response on-line computer processing in which the computer is control- ling, directing, or influencing the outcome of an activity or process in response to the data it is receiving from the activity or process. Examples of real-time operation are process control, computer-aided navigation, and reservation systems. Rehostability The capability of a programming environment, such as an APSE, to be moved to a different host computer without major modification. Rehostability is provided by the concentra- tion of all host dependencies in the KAPSE (Kernel Ada Programming Support Environment) and the runtime support libraries (see RSL). Rendezvous A rendezvous is the interaction that occurs between two parallel tasks when one task has called an entry of the other task and the other task is executing an accept statement to perform an action on behalf of the calling task. Keyword: accept. Representation A representation specification specifies specification the underlying bit patterns and/or addresses for data and programs. Keywords: for, use, at. Retargetability The capability of a programming environment, such as an APSE, to be changed to produce programs for different target computers without major modification. Retargetability of a programming environment is enhanced by designing its basic functions to be as machine independent as possible. RSL (Runtime The component of a compiler back end that Support Library) provides the additional supporting functions required for the execution of programs on a specified target computer. Since each type of target computer requires its own supporting functions, a specific runtime support library is required to turn on each type of target computer. Scalar types A scalar type is type whose values have no components. Integer types, enumera- tion types, and real types are scalar types. Scope The scope of a type or an identifier is the region of text over which the name can be used. Selected component A selected component is the identifier of the component together with the name of the structure of which it is a component. Software The methodologies and techniques used in Engineering the development of efficient, reliable, and maintainable computer software.a Software The capability of a computer program to be Portability moved between different computer systems without modification. Software porta- bility is one of the major goals of the Ada language implementation. Source Program A program written in a High Order Language such as Ada for input to a compiler. See Object Program. Static expression A static expression is one whose value does not depend on the execution of a program. Steelman The DoD document that specifies the technical requirements for the Ada language. Stoneman The DoD document that specifies the technical requirements for implementing the APSE. Subprograms A subprogram is an executable program unit that may have parameters for communication between the subprogram and its invoking program. A subprogram declaration specifies the name of the subprogram and its formal parameters. A subprogram body specifies its execution. A subprogram can be either a procedure, which performs an action, or a function, which returns a result. Keywords: procedure, function. Subtype A subtype of a type has the same opera- tions of the parent type but has a con- strained set of values. Keyword: subtype. System Life The span of time over which a system is in Cycle existence starting with its first conception and ending with its last use. System life cycles are usually divided into conceptual, development, production, and operational phases and span many years. Target Computer A computer, usually embedded in an operational system, that is designated to receive programs in its native machine language from host computers. Target computers are typically small, dedicated, special-purpose computers. Task A task is a program unit that may operate in parallel with the main program. A task specification defines the name of the task and the names and parameters of its entries. A task body defines the implementation of the task. A task type is a specification that allows the subsequent declaration of similar tasks. Keyword: task. Use clause A use clause adds the names of the visible part of a package that a program can use. Keyword: use. Variant The variant part of a record specifies alternative record components, depending on a discriminant of the record. Each value of the discriminant establishes a particular alternative of the variant part. Visibility At a given point in a program text, the declaration of an entity with an identifier is said to be visible if the entity has meaning at that point in the text.