Guide and Reference

Appendix C. Glossary

This glossary defines terms and abbreviations used in this publication. If you do not find the term you are looking for, refer to the index portion of this book. This glossary includes terms and definitions from:

APAR
Authorized Program Analysis Report. A report of a problem caused by a suspected defect in a current unaltered release of a program.

argument
A parameter passed between a calling program and a SUBROUTINE subprogram, a FUNCTION subprogram, or a statement function.

array
An ordered set of data items identified by a single name.

array element
A data item in an array, identified by the array name followed by a subscript indicating its position in the array.

array name
The name of an ordered set of data items that make up an array.

assignment statement
A statement that assigns a value to a variable or array element. It is made up of a variable or array element, followed by an equal sign (=), followed by an expression. The variable, array element, or expression can be character, logical, or arithmetic. When the assignment statement is processed, the expression to the right of the equal sign replaces the value of the variable or array element to the left.

Basic Linear Algebra Subprograms (BLAS)
A standard, public domain, set of mathematical subroutines that perform linear algebra operations.

BLAS
Basic Linear Algebra Subprograms.

cache
A special-purpose buffer storage, smaller and faster than main storage, used to hold a copy of instructions and data obtained from main storage and likely to be needed next by the processor. (T)

character constant
A string of one or more alphanumeric characters enclosed in apostrophes. The delimiting apostrophes are not part of the value of the constant.

character expression
An expression in the form of a single character constant, variable, array element, substring, function reference, or another expression enclosed in parentheses. A character expression is always of type character.

character type
The data type for representing strings of alphanumeric characters; in storage, one byte is used for each character.

column-major order
A sequencing method used for storing multidimensional arrays according to the subscripts of the array elements. In this method the leftmost subscript position varies most rapidly and completes a full cycle before the next subscript position to the right is incremented.

complex conjugate even data
Complex data that has its real part even and its imaginary part odd.

complex constant
An ordered pair of real or integer constants separated by a comma and enclosed in parentheses. The first real constant of the pair is the real part of the complex number; the second is the imaginary part.

complex type
The data type for representing an approximation of the value of a complex number. A data item of this type consists of an ordered pair of real data items separated by a comma and enclosed in parentheses. The first item represents the real part of the complex number; the second represents the imaginary part.

constant
An unvarying quantity. The four classes of constants specify numbers (arithmetic), truth values (logical), character data (character), and hexadecimal data.

data type
The structural characteristics, features and properties of data that may be directly specified by a programming language; for example, integers, real numbers in Fortran; arrays in APL; linked lists in LISP; character string in SNOBOL.

decimation
The formation of a sequence containing every n-th element of another sequence.

dimension of an array
One of the subscript expression positions in a subscript for an array. In Fortran, an array may have from one to seven dimensions. Graphically, the first dimension is represented by the rows, the second by the columns, and the third by the planes. Contrast with rank. See also extent of a dimension.

direct access storage
A storage device in which the access time is in effect independent of the location of the data. (A)

divide-by-zero exception
The condition recognized by a processor that results from running a program that attempts to divide by zero.

double precision
Synonym for long-precision.

expression
A notation that represents a value: a primary appearing alone, or combinations of primaries and operators. An expression can be arithmetic, character, logical, or relational.

extent of a dimension
The number of different integer values that may be represented by subscript expressions for a particular dimension in a subscript for an array.

external function
A function defined outside the program unit that refers to it. It may be referred to in a procedure subprogram or in the main program, but it must not refer to itself, either directly or indirectly. Contrast with statement function.

function
In Fortran, a procedure that is invoked by referring to it in an expression and that supplies a value to the expression. The value supplied is the value of the function. See also external function, intrinsic function, and statement function. Contrast with subroutine.

function reference
A Fortran source program reference to an intrinsic function, to an external function, or to a statement function.

general matrix
A matrix with no assumed special properties such as symmetry. Synonym for matrix.

integer constant
A string of decimal digits containing no decimal point and expressing a whole number.

integer expression
An arithmetic expression whose values are of integer type.

integer type
An arithmetic data type capable of expressing the value of an integer. It can have a positive, negative, or 0 value. It must not include a decimal point.

intrinsic function
A function, supplied by Fortran, that performs mathematical or character operations.

leading dimension
For a two-dimensional array, an increment used to find the starting point for the matrix elements in each successive column of the array.

logical constant
A constant that can have one of two values: true or false. The form of these values in Fortran is: .TRUE. and .FALSE. respectively.

logical expression
A logical primary alone or a combination of logical primaries and logical operators. A logical expression can have one of two values: true or false.

logical type
The data type for data items that can have the value true or false and upon which logical operations such as .NOT. and .OR. can be performed. See also "data type".

long-precision
Real type of data of length 8. Contrast with single precision and short-precision.

main program
In Fortran, a program unit, required for running, that can call other program units but cannot be called by them.

mask
To use a pattern of characters to control the retention or elimination of portions of another pattern of characters. (I)

matrix
A rectangular array of elements, arranged in rows and columns, that may be manipulated according to the rules of matrix algebra. (A) (I)

multithreaded
There may be one or more threads in a process, and each thread is executed by the operating system concurrently. An application program is multithreaded if more than one thread is executed concurrently.

overflow exception
A condition caused by the result of an arithmetic operation having a magnitude that exceeds the largest possible number.

platform
A mainframe or a workstation.

primary
An irreducible unit of data; a single constant, variable, array element, function reference, or expression enclosed in parentheses.

program exception
The condition recognized by a processor that results from running a program that improperly specifies or uses instructions, operands, or control information.

PTF
Program Temporary Fix. A temporary solution or by-pass of a problem diagnosed by IBM as resulting from a defect in a current unaltered release of the program. A report of a problem caused by a suspected defect in a current unaltered release of a program.

pthread
A thread that conforms to the POSIX Threads Programming Model.

real constant
A string of decimal digits that expresses a real number. A real constant must contain either a decimal point or a decimal exponent and may contain both. For example, the real constant 0.36819E+2 has the value +36.819.

real type
An arithmetic data type, capable of approximating the value of a real number. It can have a positive, negative, or 0 value.

row-major order
A sequencing method used for storing multidimensional arrays according to the subscripts of the array elements. In this method the rightmost subscript position varies most rapidly and completes a full cycle before the next subscript position to the left is incremented.

scalar
(1) A quantity characterized by a single number. (A) (I) (2) Contrast with vector.

shape of an array
The extents of all the dimensions of an array listed in order. For example, the shape of a three-dimensional array that has four rows, five columns, and three planes is (4,5,3) or 4 by 5 by 3.

short-precision
Real type data of length 4. Contrast with double precision and long-precision.

single precision
Synonym for short-precision.

size of an array
The number of elements in an array. This is the product of the extents of its dimensions.

SMP
Symmetric Multi-Processing.

statement
The basic unit of a program, that specifies an action to be performed, or the nature and characteristics of the data to be processed, or information about the program itself. Statements fall into two broad classes: executable and nonexecutable.

statement function
A procedure specified by a single statement that is similar in form to an arithmetic, logical, or character assignment statement. The statement must appear after the specification statements and before the first executable statement. In the remainder of the program it can be referenced as a function. A statement function may be referred to only in the program unit in which it is defined. Contrast with external function.

statement label
A number of from one through five decimal digits that is used to identify a statement. Statement labels can be used to transfer control, to define the range of a DO, or to refer to a FORMAT statement.

statement number
See "statement label".

stride
The increment used to step through array storage to select the vector or matrix elements from the array.

subprogram
A program unit that is invoked by another program unit in the same program. In Fortran, a subprogram has a FUNCTION, SUBROUTINE, or BLOCK DATA statement as its first statement.

subscript
(1) A symbol that is associated with the name of a set to identify a particular subset or element. (A) (2) A subscript expression or set of subscript expressions, enclosed in parentheses and used with an array name to identify a particular array element.

subscript expression
An integer expression in a subscript whose value and position in the subscript determine the index number for the corresponding dimension in the referenced array.

thread
A thread is the element that is scheduled, and to which resources such as execution time, locks, and queues may be assigned. There may be one or more threads in a process, and each thread is executed by the operating system concurrently.

thread-safe
A subroutine which may be called from multiple threads of the same process simultaneously.

type declaration
The explicit specification of the type of a constant, variable, array, or function by use of an explicit type specification statement.

underflow exception
A condition caused by the result of an arithmetic operation having a magnitude less than the smallest possible nonzero number.

variable
(1) A quantity that can assume any of a given set of values. (A) (2) A data item, identified by a name, that is not a named constant, array, or array element, and that can assume different values at different times during program processing.

vector
A one-dimensional ordered collection of numbers.

working storage
A storage area provided by the application program for the use of an ESSL subroutine.

workstation
A workstation is a single-user, high-performance microcomputer (or even a minicomputer) which has been specialized in some way, usually for graphics output. Such a machine has a screen and a keyboard, but is also capable of extensive processing of your input before it is passed to the host. Likewise, the host's responses may be extensively processed before being passed along to your screen. A workstation may be intelligent enough to do much or all the processing itself.

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