This glossary defines terms for all platforms and releases
of PL/I. It might contain terms that this manual does not use. If
you do not find the terms for which you are looking, see the index
in this manual or IBM Dictionary of Computing,
SC20-1699.
A
- access
- To reference or retrieve data.
- action specification
- In an ON statement, the ON-unit or the single keyword SYSTEM,
either of which specifies the action to be taken whenever the appropriate
condition is raised.
- activate (a block)
- To initiate the execution of a block. A procedure block is
activated when it is invoked. A begin-block is activated when it
is encountered in the normal flow of control, including a branch.
A package cannot be activated.
- activate (a preprocessor variable or preprocessor entry
point)
- To make a macro facility identifier eligible for replacement
in subsequent source code. The %ACTIVATE statement activates
preprocessor variables or preprocessor entry points.
- active
- The state of a block after activation and before termination.
The state in which a preprocessor variable or preprocessor entry
name is said to be when its value can replace the corresponding
identifier in source program text. The state in which an event variable
is said to be during the time it is associated with an asynchronous operation.
The state in which a task variable is said to be when its associated
task is attached. The state in which a task is said to be before
it has been terminated.
- actual origin (AO)
- The location of the first item in the array or structure.
- additive attribute
- A file description attribute for which there are no defaults,
and which, if required, must be stated explicitly or implied by
another explicitly stated attribute. Contrast with alternative attribute.
- adjustable extent
- The bound (of an array), the length (of a string), or the
size (of an area) that might be different for different generations
of the associated variable. Adjustable extents are specified as
expressions or asterisks (or by REFER options for based variables), which
are evaluated separately for each generation. They cannot be used
for static variables.
- aggregate
- See data aggregate.
- aggregate expression
- An array, structure, or union expression.
- aggregate type
- For any item of data, the specification whether it is structure,
union, or array.
- allocated variable
- A variable with which main storage is associated and not freed.
- allocation
- The reservation of main storage for a variable. A generation
of an allocated variable. The association of a PL/I file with a
system data set, device, or file.
- alignment
- The storing of data items in relation to certain machine-dependent
boundaries (for example, a fullword or halfword boundary).
- alphabetic character
- Any of the characters A through Z of the English alphabet
and the alphabetic extenders #, $, and @ (which can have a different
graphic representation in different countries).
- alphameric character
- An alphabetic character or a digit.
- alternative attribute
- A file description attribute that is chosen from a group of
attributes. If none is specified, a default is assumed. Contrast
with additive attribute.
- ambiguous reference
- A reference that is not sufficiently qualified to identify
one and only one name known at the point of reference.
- area
- A portion of storage within which based variables can be allocated.
- argument
- An expression in an argument list as part of an invocation
of a subroutine or function.
- argument list
- A parenthesized list of zero or more arguments, separated
by commas, following an entry name constant, an entry name variable,
a generic name, or a built-in function name. The list becomes the parameter
list of the entry point.
- arithmetic comparison
- A comparison of numeric values. See also bit comparison, character comparison.
- arithmetic constant
- A fixed-point constant or a floating-point constant. Although
most arithmetic constants can be signed, the sign is not part of
the constant.
- arithmetic conversion
- The transformation of a value from one arithmetic representation
to another.
- arithmetic data
- Data that has the characteristics of base, scale, mode, and
precision. Coded arithmetic data and pictured numeric character
data are included.
- arithmetic operators
- Either of the prefix operators + and -,
or any of the following infix operators: + - * / **
- array
- A named, ordered collection of one or more data elements with
identical attributes, grouped into one or more dimensions.
- array expression
- An expression whose evaluation yields an array of values.
- array of structures
- An ordered collection of identical structures specified by
giving the dimension attribute to a structure name.
- array variable
- A variable that represents an aggregate of data items that
must have identical attributes. Contrast with structure variable.
- ASCII
- American National Standard Code for Information Interchange.
- assignment
- The process of giving a value to a variable.
- asynchronous operation
- The overlap of an input/output operation with the
execution of statements. The concurrent execution of procedures
using multiple flows of control for different tasks.
- attachment of a task
- The invocation of a procedure and the establishment of a separate
flow of control to execute the invoked procedure (and procedures
it invokes) asynchronously, with execution of the invoking procedure.
- attention
- An occurrence, external to a task, that could cause a task
to be interrupted.
- attribute
- A descriptive property associated with a name to describe
a characteristic represented. A descriptive property used to describe
a characteristic of the result of evaluation of an expression.
- automatic storage allocation
- The allocation of storage for automatic variables.
- automatic variable
- A variable whose storage is allocated automatically at the
activation of a block and released automatically at the termination
of that block.
B
- base
- The number system in which an arithmetic value is represented.
- base element
- A member of a structure or a union that is itself not another
structure or union.
- base item
- The automatic, controlled, or static variable or the parameter
upon which a defined variable is defined.
- based reference
- A reference that has the based storage class.
- based storage allocation
- The allocation of storage for based variables.
- based variable
- A variable whose storage address is provided by a locator.
Multiple generations of the same variable are accessible. It does
not identify a fixed location in storage.
- begin-block
- A collection of statements delimited by BEGIN and END statements,
forming a name scope. A begin-block is activated either by the raising
of a condition (if the begin-block is the action specification for an
ON-unit) or through the normal flow of control, including any branch
resulting from a GOTO statement.
- binary
- A number system whose only numerals are 0 and 1.
- binary digit
- See bit.
- binary fixed-point value
- An integer consisting of binary digits and having an optional
binary point and optional sign. Contrast with decimal fixed-point value.
- binary floating-point value
- An approximation of a real number in the form of a significand,
which can be considered as a binary fraction, and an exponent, which can
be considered as an integer exponent to the base of 2. Contrast
with decimal floating-point value.
- bit
- A 0 or a 1. The smallest amount of space of computer storage.
- bit comparison
- A left-to-right, bit-by-bit comparison of binary digits. See
also arithmetic comparison, character comparison.
- bit string constant
- A series of binary digits enclosed in and followed immediately
by the suffix B. Contrast with character constant.
A series of hexadecimal digits enclosed in single quotes and followed
by the suffix B4.
- bit string
- A string composed of zero or more bits.
- bit string operators
- The logical operators not and exclusive-or (¬), and
(&), and or (|).
- bit value
- A value that represents a bit type.
- block
- A sequence of statements, processed as a unit, that specifies
the scope of names and the allocation of storage for names declared
within it. A block can be a package, procedure, or a begin-block.
- bounds
- The upper and lower limits of an array dimension.
- break character
- The underscore symbol ( _ ). It can be used to improve
the readability of identifiers. For instance, a variable could be
called OLD_INVENTORY_TOTAL instead of OLDINVENTORYTOTAL.
- built-in function
- A predefined function supplied by the language, such as SQRT
(square root).
- built-in function reference
- A built-in function name, which has an optional argument list.
- built-in name
- The entry name of a built-in subroutine.
- built-in subroutine
- Subroutine that has an entry name that is defined at compile-time
and is invoked by a CALL statement.
- buffer
- Intermediate storage, used in input/output operations, into
which a record is read during input and from which a record is written
during output.
C
- call
- To invoke a subroutine by using the CALL statement or CALL
option.
- character comparison
- A left-to-right, character-by-character comparison according
to the collating sequence. See also arithmetic comparison, bit comparison.
- character string constant
- A sequence of characters enclosed in single quotes; for example, 'Shakespeare''s 'Hamlet:''.
- character set
- A defined collection of characters. See language character set and data character set.
See also ASCII and EBCDIC.
- character string picture data
- Picture data that has only a character value. This type of
picture data must have at least one A or X picture specification
character. Contrast with numeric picture data.
- closing (of a file)
- The dissociation of a file from a data set or device.
- coded arithmetic data
- Data items that represent numeric values and are characterized
by their base (decimal or binary), scale (fixed-point or floating-point), and
precision (the number of digits each can have). This data is stored
in a form that is acceptable, without conversion, for arithmetic
calculations.
- combined nesting depth
- The deepest level of nesting, determined by counting the levels
of PROCEDURE/BEGIN/ON, DO, SELECT, and IF...THEN...ELSE
nestings in the program.
- comment
- A string of zero or more characters used for documentation
that are delimited by /* and */.
- commercial character
-
- CR (credit) picture specification character
- DB (debit) picture specification character
- comparison operator
- An operator that can be used in an arithmetic, string locator,
or logical relation to indicate the comparison to be done between
the terms in the relation. The comparison operators are:
- = (equal to)
- > (greater than)
- < (less than)
- >= (greater than or equal to)
- <= (less than or equal to)
- ¬= (not equal to)
- ¬> (not greater than)
- ¬< (not less than)
- compile time
- In general, the time during which a source program is translated
into an object module. In PL/I, it is the time during which a source
program can be altered, if desired, and then translated into an
object program.
- compiler options
- Keywords that are specified to control certain aspects of
a compilation, such as: the nature of the object module generated,
the types of printed output produced, and so forth.
- complex data
- Arithmetic data, each item of which consists of a real part
and an imaginary part.
- composite operator
- An operator that consists of more than one special character,
such as <=, **, and /*.
- compound statement
- A statement that contains other statements. In PL/I, IF, ON,
OTHERWISE, and WHEN are the only compound statements. See statement body.
- concatenation
- The operation that joins two strings in the order specified,
forming one string whose length is equal to the sum of the lengths
of the two original strings. It is specified by the operator ||.
- condition
- An exceptional situation, either an error (such as an overflow),
or an expected situation (such as the end of an input file). When
a condition is raised (detected), the action established for it
is processed. See also established action and implicit action.
- condition name
- Name of a PL/I-defined or programmer-defined condition.
- condition prefix
- A parenthesized list of one or more condition names prefixed
to a statement. It specifies whether the named conditions are to
be enabled or disabled.
- connected aggregate
- An array or structure whose elements occupy contiguous storage
without any intervening data items. Contrast with nonconnected aggregate.
- connected reference
- A reference to connected storage. It must be apparent, prior
to execution of the program, that the storage is connected.
- connected storage
- Main storage of an uninterrupted linear sequence of items
that can be referred to by a single name.
- constant
- An arithmetic or string data item that does not have a name
and whose value cannot change. An identifier declared with the VALUE
attribute. An identifier declared with the FILE or the ENTRY attribute
but without the VARIABLE attribute.
- constant reference
- A value reference which has a constant as its object
- contained block, declaration, or source text
- All blocks, procedures, statements, declarations, or source text
inside a begin, procedure, or a package block. The entire package,
procedure, and the BEGIN statement and its corresponding END statements
are not contained in the block.
- containing block
- The package, procedure, or begin-block that contains the declaration,
statement, procedure, or other source text in question.
- contextual declaration
- The appearance of an identifier that has not been explicitly
declared in a DECLARE statement, but whose context of use allows
the association of specific attributes with the identifier.
- control character
- A character in a character set whose occurrence in a particular
context specifies a control function. One example is the end-of-file
(EOF) marker.
- control format item
- A specification used in edit-directed transmission to specify
positioning of a data item within the stream or printed page.
- control variable
- A variable that is used to control the iterative execution
of a DO statement.
- controlled parameter
- A parameter for which the CONTROLLED attribute is specified
in a DECLARE statement. It can be associated only with arguments
that have the CONTROLLED attribute.
- controlled storage allocation
- The allocation of storage for controlled variables.
- controlled variable
- A variable whose allocation and release are controlled by
the ALLOCATE and FREE statements, with access to the current generation
only.
- control sections
- Grouped machine instructions in an object module.
- conversion
- The transformation of a value from one representation to another
to conform to a given set of attributes. For example, converting
a character string to an arithmetic value such as FIXED BINARY (15,0).
- cross section of an array
- The elements represented by the extent of at least one dimension
of an array. An asterisk in the place of a subscript in an array
reference indicates the entire extent of that dimension.
- current generation
- The generation of an automatic or controlled variable that
is currently available by referring to the name of the variable.
D
- data
- Representation of information or of value in a form suitable
for processing.
- data aggregate
- A data item that is a collection of other data items.
- data attribute
- A keyword that specifies the type of data that the data item
represents, such as FIXED BINARY.
- data-directed transmission
- The type of stream-oriented transmission in which data is
transmitted. It resembles an assignment statement and is of the
form name = constant.
- data item
- A single named unit of data.
- data list
- In stream-oriented transmission, a parenthesized list of the
data items used in GET and PUT statements. Contrast with format list.
- data set
- A collection of data external to the program that can be accessed
by reference to a single file name. A device that can be referenced.
- data specification
- The portion of a stream-oriented transmission statement that
specifies the mode of transmission (DATA, LIST, or EDIT) and includes
the data list(s) and, for edit-directed mode, the format list(s).
- data stream
- Data being transferred from or to a data set by stream-oriented
transmission, as a continuous stream of data elements in character
form.
- data transmission
- The transfer of data from a data set to the program or vice
versa.
- data type
- A set of data attributes.
- DBCS
- In the character set, each character is represented by two
consecutive bytes.
- deactivated
- The state in which an identifier is said to be when its value
cannot replace a preprocessor identifier in source program text.
Contrast with active.
- debugging
- Process of removing bugs from a program.
- decimal
- The number system whose numerals are 0 through 9.
- decimal digit picture character
- The picture specification character 9.
- decimal fixed-point constant
- A constant consisting of one or more decimal digits with an
optional decimal point.
- decimal fixed-point value
- A rational number consisting of a sequence of decimal digits
with an assumed position of the decimal point. Contrast with binary fixed-point value.
- decimal floating-point constant
- A value made up of a significand that consists of a decimal
fixed-point constant, and an exponent that consists of the letter
E followed by an optionally signed integer constant not exceeding
three digits.
- decimal floating-point value
- An approximation of a real number, in the form of a significand,
which can be considered as a decimal fraction, and an exponent,
which can be considered as an integer exponent to the base 10. Contrast
with binary floating-point value.
- decimal picture data
- See numeric picture data.
- declaration
- The establishment of an identifier as a name and the specification
of a set of attributes (partial or complete) for it. A source of
attributes of a particular name.
- default
- Describes a value, attribute, or option that is assumed when
none has been specified.
- defined variable
- A variable that is associated with some or all of the storage
of the designated base variable.
- delimit
- To enclose one or more items or statements with preceding
and following characters or keywords.
- delimiter
- All comments and the following characters: percent,
parentheses, comma, period, semicolon, colon, assignment symbol,
blank, pointer, asterisk, and single quote. They define the limits
of identifiers, constants, picture specifications, iSUBs, and keywords.
- descriptor
- A control block that holds information about a variable, such
as area size, array bounds, or string length.
- digit
- One of the characters 0 through 9.
- dimension attribute
- An attribute that specifies the number of dimensions of an
array and indicates the bounds of each dimension.
- disabled
- The state of a condition in which no interrupt occurs and
no established action will take place.
- do-group
- A sequence of statements delimited by a DO statement and ended
by its corresponding END statement, used for control purposes. Contrast
with block.
- do-loop
- See iterative do-group.
- dummy argument
- Temporary storage that is created automatically to hold the
value of an argument that cannot be passed by reference.
- dump
- Printout of all or part of the storage used by a program as
well as other program information, such as a trace of an error's
origin.
E
- EBCDIC
- (Extended Binary-Coded Decimal Interchange Code). A coded
character set consisting of 8-bit coded characters.
- edit-directed transmission
- The type of stream-oriented transmission in which data appears
as a continuous stream of characters and for which a format list
is required to specify the editing desired for the associated data
list.
- element
- A single item of data as opposed to a collection of data items
such as an array; a scalar item.
- element expression
- An expression whose evaluation yields an element value.
- element variable
- A variable that represents an element; a scalar variable.
- elementary name
- See base element.
- enabled
- The state of a condition in which the condition can cause
an interrupt and then invocation of the appropriate established
ON-unit.
- end-of-step message
- message that follows the listng of the job control statements
and job scheduler messages and contains return code indicating success
or failure for each step.
- entry constant
- The label prefix of a PROCEDURE statement (an entry name).
The declaration of a name with the ENTRY attribute but without the
VARIABLE attribute.
- entry data
- A data item that represents an entry point to a procedure.
- entry expression
- An expression whose evaluation yields an entry name.
- entry name
- An identifier that is explicitly or contextually declared
to have the ENTRY attribute (unless the VARIABLE attribute is given)
or An identifier that has the value of an entry variable with the
ENTRY attribute implied.
- entry point
- A point in a procedure at which it can be invoked. primary entry point and secondary entry point.
- entry reference
- An entry constant, an entry variable reference, or a function
reference that returns an entry value.
- entry variable
- A variable to which an entry value can be assigned. It must
have both the ENTRY and VARIABLE attributes.
- entry value
- The entry point represented by an entry constant or variable; the
value includes the environment of the activation that is associated
with the entry constant.
- environment (of an activation)
- Information associated with and used in the invoked block
regarding data declared in containing blocks.
- environment (of a label constant)
- Identity of the particular activation of a block to which
a reference to a statement-label constant applies. This information
is determined at the time a statement-label constant is passed as
an argument or is assigned to a statement-label variable, and it
is passed or assigned along with the constant.
- established action
- The action taken when a condition is raised. See also implicit action and ON-statement action.
- epilogue
- Those processes that occur automatically at the termination
of a block or task.
- evaluation
- The reduction of an expression to a single value, an array
of values, or a structured set of values.
- event
- An activity in a program whose status and completion can be
determined from an associated event variable.
- event variable
- A variable with the EVENT attribute that can be associated
with an event. Its value indicates whether the action has been completed
and the status of the completion.
- explicit declaration
- The appearance of an identifier (a name) in a DECLARE statement,
as a label prefix, or in a parameter list. Contrast with implicit declaration.
- exponent characters
- The following picture specification characters:
- K and E, which are used in floating-point picture specifications
to indicate the beginning of the exponent field.
- F, the scaling factor character, specified with an integer constant
that indicates the number of decimal positions the decimal point
is to be moved from its assumed position to the right (if the constant
is positive) or to the left (if the constant is negative).
- expression
- A notation, within a program, that represents a value, an
array of values, or a structured set of values. A constant or a
reference appearing alone, or a combination of constants and/or
references with operators.
- extended alphabet
- The uppercase and lowercase alphabetic characters A through
Z, $, @ and #, or those specified in
the NAMES compiler option.
- extent
- The range indicated by the bounds of an array dimension, by
the length of a string, or by the size of an area. The size of the
target area if this area were to be assigned to a target area.
- external name
- A name (with the EXTERNAL attribute) whose scope is not necessarily
confined only to one block and its contained blocks.
- external procedure
- A procedure that is not contained in any other procedure.
A level-2 procedure contained in a package that is also exported.
- external symbol
- Name that can be referred to in a control section other than
the one in which it is defined.
- External Symbol Dictionary (ESD)
- Table containing all the external symbols that appear in the
object module.
- extralingual character
- Characters (such as $, @, and #)
that are not classified as alphanumeric or special. This group includes
characters that are determined with the NAMES compiler option.
F
- factoring
- The application of one or more attributes to a parenthesized
list of names in a DECLARE statement, eliminating the repetition
of identical attributes for multiple names.
- field (in the data stream)
- That portion of the data stream whose width, in number of
characters, is defined by a single data or spacing format item.
- field (of a picture specification)
- Any character-string picture specification or that portion
(or all) of a numeric character picture specification that describes
a fixed-point number.
- file
- A named representation, within a program, of a data set or
data sets. A file is associated with the data set(s) for each opening.
- file constant
- A name declared with the FILE attribute but not the VARIABLE
attribute.
- file description attributes
- Keywords that describe the individual characteristics of each
file constant. See also alternative attribute and additive attribute.
- file expression
- An expression whose evaluation yields a value of the type
file.
- file name
- A name declared for a file.
- file variable
- A variable to which file constants can be assigned. It has
the attributes FILE and VARIABLE and cannot have any of the file
description attributes.
- fixed-point constant
- See arithmetic constant.
- fix-up
- A solution, performed by the compiler after detecting an error
during compilation, that allows the compiled program to run.
- floating-point constant
- See arithmetic constant.
- flow of control
- Sequence of execution.
- format
- A specification used in edit-directed data transmission to
describe the representation of a data item in the stream (data format
item) or the specific positioning of a data item within the stream
(control format item).
- format constant
- The label prefix on a FORMAT statement.
- format data
- A variable with the FORMAT attribute.
- format label
- The label prefix on a FORMAT statement.
- format list
- In stream-oriented transmission, a list specifying the format
of the data item on the external medium. Contrast with data list.
- fully qualified name
- A name that includes all the names in the hierarchical sequence
above the member to which the name refers, as well as the name of
the member itself.
- function (procedure)
- A procedure that has a RETURNS option in the PROCEDURE statement.
A name declared with the RETURNS attribute. It is invoked by the
appearance of one of its entry names in a function reference and
it returns a scalar value to the point of reference. Contrast with subroutine.
- function reference
- An entry constant or an entry variable, either of which must
represent a function, followed by a possibly empty argument list.
Contrast with subroutine call.
G
- generation (of a variable)
- The allocation of a static variable, a particular allocation
of a controlled or automatic variable, or the storage indicated
by a particular locator qualification of a based variable or by
a defined variable or parameter.
- generic descriptor
- A descriptor used in a GENERIC attribute.
- generic key
- A character string that identifies a class of keys. All keys
that begin with the string are members of that class. For example,
the recorded keys 'ABCD', 'ABCE',
and 'ABDF', are all members of the classes identified
by the generic keys 'A' and 'AB',
and the first two are also members of the class 'ABC'; and
the three recorded keys can be considered to be unique members of
the classes 'ABCD', 'ABCE', 'ABDF',
respectively.
- generic name
- The name of a family of entry names. A reference to the generic
name is replaced by the entry name whose parameter descriptors match
the attributes of the arguments in the argument list at the point
of invocation.
- group
- A collection of statements contained within larger program
units. A group is either a do-group or a select-group and it can
be used wherever a single statement can appear, except as an on-unit.
H
- hex
- See hexadecimal digit.
- hexadecimal
- Pertaining to a numbering system with a base of sixteen; valid
numbers use the digits 0 through 9 and the characters A through
F, where A represents 10 and F represents 15.
- hexadecimal digit
- One of the digits 0 through 9 and A through F. A through F
represent the decimal values 10 through 15, respectively.
I
- identifier
- A string of characters, not contained in a comment or constant,
and preceded and followed by a delimiter. The first character of
the identifier must be one of the 26 alphabetic characters and extralingual characters,
if any. The other characters, if any, can additionally include extended
alphabetic, digit, or the break character.
- IEEE
- Institute of Electrical and Electronics Engineers.
- implicit
- The action taken in the absence of an explicit specification.
- implicit action
- The action taken when an enabled condition is raised and no
ON-unit is currently established for the condition. Contrast with ON-statement action.
- implicit declaration
- A name not explicitly declared in a DECLARE statement or contextually
declared.
- implicit opening
- The opening of a file as the result of an input or output
statement other than the OPEN statement.
- infix operator
- An operator that appears between two operands.
- inherited dimensions
- For a structure, union, or element, those dimensions that
are derived from the containing structures. If the name is an element
that is not an array, the dimensions consist entirely of its inherited dimensions.
If the name is an element that is an array, its dimensions consist
of its inherited dimensions plus its explicitly declared dimensions.
A structure with one or more inherited dimensions is called a nonconnected aggregate.
Contrast with connected aggregate.
- input/output
- The transfer of data between auxiliary medium and main storage.
- insertion point character
- A picture specification character that is, on assignment of
the associated data to a character string, inserted in the indicated
position. When used in a P-format item for input, the insertion character
is used for checking purposes.
- integer
- An optionally signed sequence of digits or a sequence of bits
without a decimal or binary point. An optionally signed whole number,
commonly described as FIXED BINARY (p,0) or FIXED DECIMAL (p,0).
- integral boundary
- A byte multiple address of any 8-bit unit on which data can
be aligned. It usually is a halfword, fullword, or doubleword (2-,
4-, or 8-byte multiple respectively) boundary.
- interleaved array
- An array that refers to nonconnected storage.
- interleaved subscripts
- Subscripts that exist in levels other than the lowest level
of a subscripted qualified reference.
- internal block
- A block that is contained in another block.
- internal name
- A name that is known only within the block in which it is
declared, and possibly within any contained blocks.
- internal procedure
- A procedure that is contained in another block. Contrast with external procedure.
- interrupt
- The redirection of the program's flow of control as the result
of raising a condition or attention.
- invocation
- The activation of a procedure.
- invoke
- To activate a procedure.
- invoked procedure
- A procedure that has been activated.
- invoking block
- A block that activates a procedure.
- iteration factor
- In an INITIAL attribute specification, an expression that
specifies the number of consecutive elements of an array that are
to be initialized with the given value. In a format list, an expression
that specifies the number of times a given format item or list of
format items is to be used in succession.
- iterative do-group
- A do-group whose DO statement specifies a control variable
and/or a WHILE or UNTIL option.
K
- key
- Data that identifies a record within a direct-access data
set. See source key and recorded key.
- keyword
- An identifier that has a specific meaning in PL/I when used
in a defined context.
- keyword statement
- A simple statement that begins with a keyword, indicating
the function of the statement.
- known (applied to a name)
- Recognized with its declared meaning. A name is known throughout
its scope.
L
- label
- A name prefixed to a statement. A name on a PROCEDURE statement
is called an entry constant; a name on a FORMAT statement is called
a format constant; a name on other kinds of statements is called
a label constant. A data item that has the LABEL attribute.
- label constant
- A name written as the label prefix of a statement (other than
PROCEDURE, ENTRY, FORMAT, or PACKAGE) so that, during execution,
program control can be transferred to that statement through a reference to
its label prefix.
- label data
- A label constant or the value of a label variable.
- label prefix
- A label prefixed to a statement.
- label variable
- A variable declared with the LABEL attribute. Its value is
a label constant in the program.
- leading zeroes
- Zeros that have no significance in an arithmetic value. All
zeros to the left of the first nonzero in a number.
- level number
- A number that precedes a name in a DECLARE statement and specifies
its relative position in the hierarchy of structure names.
- level-one variable
- A major structure or union name. Any unsubscripted variable
not contained within a structure or union.
- lexically
- Relating to the left-to-right order of units.
- library
- An MVS partitioned data set or a CMS MACLIB that can be used
to store other data sets called members.
- list-directed
- The type of stream-oriented transmission in which data in
the stream appears as constants separated by blanks or commas and
for which formatting is provided automatically.
- locator
- A control block that holds the address of a variable or its
descriptor.
- locator/descriptor
- A locator followed by a descriptor. The locator holds the
address of the variable, not the address of the descriptor.
- locator qualification
- In a reference to a based variable, either a locator variable
or function reference connected by an arrow to the left of a based
variable to specify the generation of the based variable to which
the reference refers. It might be an implicit reference.
- locator value
- A value that identifies or can be used to identify the storage
address.
- locator variable
- A variable whose value identifies the location in main storage
of a variable or a buffer. It has the POINTER or OFFSET attribute.
- locked record
- A record in an EXCLUSIVE DIRECT UPDATE file that has been
made available to one task only and cannot be accessed by other
tasks until the task using it relinquishes it.
- logical level (of a structure or union member)
- The depth indicated by a level number when all level numbers are
in direct sequence (when the increment between successive level
numbers is one).
- logical operators
- The bit-string operators not and exclusive-or (¬),
and (&), and or (|).
- loop
- A sequence of instructions that is executed iteratively.
- lower bound
- The lower limit of an array dimension.
M
- main procedure
- An external procedure whose PROCEDURE statement has the OPTIONS
(MAIN) attribute. This procedure is invoked automatically as the first
step in the execution of a program.
- major structure
- A structure whose name is declared with level number 1.
- member
- A structure, union, or element name in a structure or union.
Data sets in a library.
- minor structure
- A structure that is contained within another structure or
union. The name of a minor structure is declared with a level number
greater than one and greater than its parent structure or union.
- mode (of arithmetic data)
- An attribute of arithmetic data. It is either real or complex.
- multiple declaration
- Two or more declarations of the same identifier internal to
the same block without different qualifications. Two or more external
declarations of the same identifier.
- multiprocessing
- The use of a computing system with two or more processing
units to execute two or more programs simultaneously.
- multiprogramming
- The use of a computing system to execute more than one program
concurrently, using a single processing unit.
N
- name
- Any identifier that the user gives to a variable or to a constant.
An identifier appearing in a context where it is not a keyword.
Sometimes called a user-defined name.
- nesting
- The occurrence of:
- A block within another block
- A group within another group
- An IF statement in a THEN clause or in an ELSE clause
- A function reference as an argument of a function reference
- A remote format item in the format list of a FORMAT statement
- A parameter descriptor list in another parameter descriptor
list
- An attribute specification within a parenthesized name list
for which one or more attributes are being factored
- nonconnected storage
- Storage occupied by nonconnected data items. For example,
interleaved arrays and structures with inherited dimensions are
in nonconnected storage.
- null locator value
- A special locator value that cannot identify any location
in internal storage. It gives a positive indication that a locator
variable does not currently identify any generation of data.
- null statement
- A statement that contains only the semicolon symbol (;). It
indicates that no action is to be taken.
- null string
- A character, graphic, or bit string with a length of zero.
- numeric-character data
- See decimal picture data.
- numeric picture data
- Picture data that has an arithmetic value as well as a character
value. This type of picture data cannot contain the characters 'A' or 'X.'
O
- object
- A collection of data referred to by a single name.
- offset variable
- A locator variable with the OFFSET attribute, whose value
identifies a location in storage relative to the beginning of an
area.
- ON-condition
- An occurrence, within a PL/I program, that could cause a program
interrupt. It can be the detection of an unexpected error or of
an occurrence that is expected, but at an unpredictable time.
- ON-statement action
- The action explicitly established for a condition that is
executed when the condition is raised. When the ON-statement is
encountered in the flow of control for the program, it executes,
establishing the action for the condition. The action executes when
the condition is raised if the ON-unit is still established or a RESIGNAL
statement reestablishes it. Contrast with implicit action.
- ON-unit
- The specified action to be executed when the appropriate condition
is raised.
- opening (of a file)
- The association of a file with a data set.
- operand
- The value of an identifier, constant, or an expression to
which an operator is applied, possibly in conjunction with another
operand.
- operational expression
- An expression that consists of one or more operators.
- operator
- A symbol specifying an operation to be performed.
- option
- A specification in a statement that can be used to influence
the execution or interpretation of the statement.
P
- package constant
- The label prefix on a PACKAGE statement.
- packed decimal
- The internal representation of a fixed-point decimal data
item.
- padding
- One or more characters, graphics, or bits concatenated to
the right of a string to extend the string to a required length.
One or more bytes or bits inserted in a structure or union so that
the following element within the structure or union is aligned on
the appropriate integral boundary.
- parameter
- A name in the parameter list following the PROCEDURE statement,
specifying an argument that will be passed when the procedure is
invoked.
- parameter descriptor
- The set of attributes specified for a parameter in an ENTRY
attribute specification.
- parameter descriptor list
- The list of all parameter descriptors in an ENTRY attribute
specification.
- parameter list
- A parenthesized list of one or more parameters, separated
by commas and following either the keyword PROCEDURE in a procedure
statement or the keyword ENTRY in an ENTRY statement. The list corresponds
to a list of arguments passed at invocation.
- partially qualified name
- A qualified name that is incomplete. It includes one or more,
but not all, of the names in the hierarchical sequence above the
structure or union member to which the name refers, as well as the name
of the member itself.
- picture data
- Numeric data, character data, or a mix of both types, represented
in character form.
- picture specification
- A data item that is described using the picture characters
in a declaration with the PICTURE attribute or in a P-format item.
- picture specification character
- Any of the characters that can be used in a picture specification.
- PL/I character set
- A set of characters that has been defined to represent program
elements in PL/I.
- PL/I prompter
- Command processor program for the PLI command that checks
the operands and allocates the data sets required by the compiler.
- point of invocation
- The point in the invoking block at which the reference to
the invoked procedure appears.
- pointer
- A type of variable that identifies a location in storage.
- pointer value
- A value that identifies the pointer type.
- pointer variable
- A locator variable with the POINTER attribute that contains
a pointer value.
- precision
- The number of digits or bits contained in a fixed-point data
item, or the minimum number of significant digits (excluding the
exponent) maintained for a floating-point data item.
- prefix
- A label or a parenthesized list of one or more condition names
included at the beginning of a statement.
- prefix operator
- An operator that precedes an operand and applies only to that
operand. The prefix operators are plus (+), minus (-),
and not (¬).
- preprocessor
- A program that examines the source program before the compilation
takes place.
- preprocessor statement
- A special statement appearing in the source program that specifies
the actions to be performed by the preprocessor. It is executed
as it is encountered by the preprocessor.
- primary entry point
- The entry point identified by any of the names in the label
list of the PROCEDURE statement.
- priority
- A value associated with a task, that specifies the precedence
of the task relative to other tasks.
- problem data
- Coded arithmetic, bit, character, graphic, and picture data.
- problem-state program
- A program that operates in the problem state of the operating
system. It does not contain input/output instructions or other privileged
instructions.
- procedure
- A collection of statements, delimited by PROCEDURE and END
statements. A procedure is a program or a part of a program, delimits
the scope of names, and is activated by a reference to the procedure or
one of its entry names. See also external procedure and internal procedure.
- procedure reference
- An entry constant or variable. It can be followed by an argument
list. It can appear in a CALL statement or the CALL option, or as
a function reference.
- program
- A set of one or more external procedures or packages. One
of the external procedures must have the OPTIONS(MAIN) specification
in its procedure statement.
- program control data
- Area, locator, label, format, entry, and file data that is
used to control the processing of a PL/I program.
- prologue
- The processes that occur automatically on block activation.
- pseudovariable
- Any of the built-in function names that can be used to specify
a target variable. It is usually on the left-hand side of an assignment
statement.
Q
- qualified name
- A hierarchical sequence of names of structure or union members,
connected by periods, used to identify a name within a structure.
Any of the names can be subscripted.
R
- range (of a default specification)
- A set of identifiers and/or parameter descriptors to which
the attributes in a DEFAULT statement apply.
- record
- The logical unit of transmission in a record-oriented input
or output operation. A collection of one or more related data items.
The items usually have different data attributes and usually are
described by a structure or union declaration.
- recorded key
- A character string identifying a record in a direct-access
data set where the character string itself is also recorded as part
of the data.
- record-oriented data transmission
- The transmission of data in the form of separate records.
Contrast with stream data transmission.
- recursive procedure
- A procedure that can be called from within itself or from
within another active procedure.
- reentrant procedure
- A procedure that can be activated by multiple tasks, threads,
or processes simultaneously without causing any interference between
these tasks, threads, and processes.
- REFER expression
- The expression preceding the keyword REFER, which is used
as the bound, length, or size when the based variable containing
a REFER option is allocated, either by an ALLOCATE or LOCATE statement.
- REFER object
- The variable in a REFER option that holds or will hold the
current bound, length, or size for the member. The REFER object
must be a member of the same structure or union. It must not be
locator-qualified or subscripted, and it must precede the member
with the REFER option.
- reference
- The appearance of a name, except in a context that causes
explicit declaration.
- relative virtual origin (RVO)
- The actual origin of an array minus the virtual origin of
an array.
- remote format item
- The letter R followed by the label (enclosed in parentheses)
of a FORMAT statement. The format statement is used by edit-directed
data transmission statements to control the format of data being
transmitted.
- repetition factor
- A parenthesized unsigned integer constant that specifies:
- The number of times the string constant that follows is to be
repeated.
- The number of times the picture character that follows is to
be repeated.
- repetitive specification
- An element of a data list that specifies controlled iteration
to transmit one or more data items, generally used in conjunction
with arrays.
- restricted expression
- An expression that can be evaluated by the compiler during
compilation, resulting in a constant. Operands of such an expression
are constants, named constants, and restricted expressions.
- returned value
- The value returned by a function procedure.
- RETURNS descriptor
- A descriptor used in a RETURNS attribute, and in the RETURNS
option of the PROCEDURE and ENTRY statements.
S
- scalar variable
- A variable that is not a structure, union, or array.
- scale
- A system of mathematical notation whose representation of
an arithmetic value is either fixed-point or floating-point.
- scale factor
- A specification of the number of fractional digits in a fixed-point
number.
- scaling factor
- See scale factor.
- scope (of a condition prefix)
- The portion of a program throughout which a particular condition
prefix applies.
- scope (of a declaration or name)
- The portion of a program throughout which a particular name
is known.
- secondary entry point
- An entry point identified by any of the names in the label
list of an entry statement.
- select-group
- A sequence of statements delimited by SELECT and END statements.
- selection clause
- A WHEN or OTHERWISE clause of a select-group.
- self-defining data
- An aggregate that contains data items whose bounds, lengths,
and sizes are determined at program execution time and are stored
in a member of the aggregate.
- separator
- See delimiter.
- shift
- Change of data in storage to the left or to the right of original
position.
- shift-in
- Symbol used to signal the compiler at the end of a double-byte
string.
- shift-out
- Symbol used to signal the compiler at the beginning of a double-byte
string.
- sign and currency symbol characters
- The picture specification characters. S, +, -,
and $ (or other national currency symbols enclosed in < and >).
- simple parameter
- A parameter for which no storage class attribute is specified.
It can represent an argument of any storage class, but only the
current generation of a controlled argument.
- simple statement
- A statement other than IF, ON, WHEN, and OTHERWISE.
- source
- Data item to be converted for problem data.
- source key
- A key referred to in a record-oriented transmission statement
that identifies a particular record within a direct-access data
set.
- source program
- A program that serves as input to the source program processors
and the compiler.
- source variable
- A variable whose value participates in some other operation,
but is not modified by the operation. Contrast with target variable.
- spill file
- Data set named SYSUT1 that is used as a temporary workfile.
- standard default
- The alternative attribute or option assumed when none has
been specified and there is no applicable DEFAULT statement.
- standard file
- A file assumed by PL/I in the absence of a FILE or STRING
option in a GET or PUT statement. SYSIN is the standard input file
and SYSPRINT is the standard output file.
- standard system action
- Action specified by the language to be taken for an enabled
condition in the absence of an ON-unit for that condition.
- statement
- A PL/I statement, composed of keywords, delimiters, identifiers,
operators, and constants, and terminated by a semicolon (;). Optionally,
it can have a condition prefix list and a list of labels. See also keyword statement, assignment statement,
and null statement.
- statement body
- A statement body can be either a simple or a compound statement.
- statement label
- See label constant.
- static storage allocation
- The allocation of storage for static variables.
- static variable
- A variable that is allocated before execution of the program
begins and that remains allocated for the duration of execution.
- stream-oriented data transmission
- The transmission of data in which the data is treated as though
it were a continuous stream of individual data values in character form.
Contrast with record-oriented data transmission.
- string
- A contiguous sequence of characters, graphics, or bits that
is treated as a single data item.
- string variable
- A variable declared with the BIT, CHARACTER, or GRAPHIC attribute,
whose values can be either bit, character, or graphic strings.
- structure
- A collection of data items that need not have identical attributes.
Contrast with array.
- structure expression
- An expression whose evaluation yields a structure set of values.
- structure of arrays
- A structure that has the dimension attribute.
- structure member
- See member.
- structuring
- The hierarchy of a structure, in terms of the number of members,
the order in which they appear, their attributes, and their logical
level.
- subroutine
- A procedure that has no RETURNS option in the PROCEDURE statement.
Contrast with function.
- subroutine call
- An entry reference that must represent a subroutine, followed
by an optional argument list that appears in a CALL statement. Contrast
with function reference.
- subscript
- An element expression that specifies a position within a dimension
of an array. If the subscript is an asterisk, it specifies all of
the elements of the dimension.
- subscript list
- A parenthesized list of one or more subscripts, one for each
dimension of the array, which together uniquely identify either
a single element or cross section of the array.
- subtask
- A task that is attached by the given task or any of the tasks
in a direct line from the given task to the last attached task.
- synchronous
- A single flow of control for serial execution of a program.
T
- target
- Attributes to which a data item (source) is converted.
- target reference
- A reference that designates a receiving variable (or a portion
of a receiving variable).
- target variable
- A variable to which a value is assigned.
- task
- The execution of one or more procedures by a single flow of
control.
- task name
- An identifier used to refer to a task variable.
- task variable
- A variable with the TASK attribute whose value gives the relative
priority of a task.
- termination (of a block)
- Cessation of execution of a block, and the return of control
to the activating block by means of a RETURN or END statement, or
the transfer of control to the activating block or to some other
active block by means of a GO TO statement.
- termination (of a task)
- Cessation of the flow of control for a task.
- truncation
- The removal of one or more digits, characters, graphics, or
bits from one end of an item of data when a string length or precision
of a target variable has been exceeded.
- type
- The set of data attributes and storage attributes that apply
to a generation, a value, or an item of data.
U
- undefined
- Indicates something that a user must not do. Use of a undefined
feature is likely to produce different results on different implementations
of a PL/I product. In that case, the application program is in error.
- union
- A collection of data elements that overlay each other, occupying
the same storage. The members can be structures, unions, elementary
variables, or arrays. They need not have identical attributes.
- union of arrays
- A union that has the DIMENSION attribute.
- upper bound
- The upper limit of an array dimension.
V
- value reference
- A reference used to obtain the value of an item of data.
- variable
- A named entity used to refer to data and to which values can
be assigned. Its attributes remain constant, but it can refer to
different values at different times.
- variable reference
- A reference that designates all or part of a variable.
- virtual origin (VO)
- The location where the element of the array whose subscripts
are all zero are held. If such an element does not appear in the
array, the virtual origin is where it would be held.
Z
- zero-suppression characters
- The picture specification characters Z and *, which are used
to suppress zeros in the corresponding digit positions and replace
them with blanks or asterisks respectively.
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