Essential Introduction
Note: this document is essential reading for any prospective user of the Library.
1 The Library and its Documentation
1.1 Structure of the Library
The NAG Fortran Library is a comprehensive collection of routines for the solution of numerical and statistical problems. The word ‘routine’ is used to denote ‘subroutine’ or ‘function’.
The Library is divided into chapters, each devoted to a branch of numerical analysis or statistics. Each chapter has a threecharacter name and a title,
e.g.,
Exceptionally, Chapters
H and
S have onecharacter names. (The chapters and their names are based on the ACM modified SHARE classification index (see
ACM (1960–1976)).)
All documented routines in the Library have sixcharacter names, beginning with the characters of the chapter name,
e.g.,
Note that the second and third characters are
digits, not letters; e.g., 0 is the digit zero, not the letter O. The last letter of each routine name almost always appears as
‘F’ in the documentation, but may be changed to ‘E’ in some single precision implementations (see Section
1.5). Chapters
C05,
D03 and
E04 have some routines whose last letter is ‘A’ rather than ‘F’ (‘B’ in some single precision implementations). An ‘A’ version
is always paired with an ‘F’ routine, the ‘A’ version being safe to use in a multithreaded environment, but otherwise having
identical functionality to the ‘F’ version.
Chapter
F06 (
Linear Algebra Support Routines) contains all the Basic Linear Algebra Subprograms, BLAS, with NAGstyle names as well as with the actual BLAS names, e.g.,
F06PAF (DGEMV). The names in brackets are the equivalent double precision BLAS names. Chapter
F07 (
Linear Equations (LAPACK)) and Chapter
F08 (
Leastsquares and Eigenvalue Problems (LAPACK)) contain routines derived from the LAPACK project. Like the BLAS, these routines have NAGstyle names as well as LAPACK
names, e.g.,
F07ADF (DGETRF). Details regarding these alternate names can be found in the relevant Chapter Introductions.
In order to take full advantage of machinespecific versions of BLAS and LAPACK routines provided by some computer hardware
vendors, you are encouraged to use the BLAS and LAPACK names (e.g.,
DGEMV and
DGETRF) rather than the corresponding NAGstyle names (e.g.,
F06PAF and
F07ADF) wherever possible in your programs.
1.2 Structure of the Documentation
The NAG Fortran Library Manual is the principal documentation for the NAG Fortran Library. It has the same chapter structure as the Library: each chapter
of routines in the Library has a corresponding chapter (of the same name) in the Manual. The chapters occur in alphanumeric
order. General introductory documents are placed in Volume 1 of the Manual.
Each chapter consists of the following documents:
 Chapter Contents, e.g., Contents – D01;
 Chapter Introduction, e.g., Introduction – D01;
 Routine Documents, one for each documented routine in the chapter.
A routine document has the same name as the routine which it describes. Within each chapter, routine documents occur in alphanumeric
order. For those chapters that have both ‘A’ and ‘F’ versions of a routine, the routine descriptions are combined into one
routine document. Exceptionally, some chapters (Chapters
X01 and
X02) do not have individual routine documents; instead, all the routines are described together in the Chapter Introduction.
Currently NAG provides documentation in the form of unlinked PDF files accompanied by an HTML index. Introductory material
is provided in both PDF and HTML but the
Keyword Index and
GAMS Classification Index are provided in HTML only. It is anticipated that future releases will provide HTML files (taking advantage of technology
that is currently being developed, e.g., MathML) for the full manual and fully linked PDF files for all but the
Keyword Index and
GAMS Classification Index. The most uptodate version of the documentation is accessible via the NAG Web site (see Section
4).
1.3 Marks of the Library
Periodically a new Mark of the NAG Fortran Library is released: new routines are added, corrections and/or improvements are made to existing routines;
occasionally routines are withdrawn if they have been superseded by improved routines.
At each Mark, the documentation of the Library is updated. You must make sure that your documentation has been updated to
the same Mark as the Library software that you are using.
Marks are numbered, e.g., 4, 5, 6. The current Mark is
Mark 21.
1.4 Implementations of the Library
The NAG Fortran Library is available on many different computer systems. For each distinct system, an implementation of the Library is prepared by NAG, e.g., the Sun Solaris implementation. The implementation is distributed to sites as a
tested compiled library.
An implementation is usually specific to a range of machines (e.g., the Linux 32bit range); it may also be specific to a
particular operating system, Fortran compiler, or compiler option (such as scalar or vector mode or thread safe).
Essentially the same facilities are provided in all implementations of the Library, but, because of differences in arithmetic
behaviour and in the compilation system, routines cannot be expected to give identical results on different systems, especially
for sensitive numerical problems.
The documentation supports all implementations of the Library, with the help of a few simple conventions, and a small amount
of implementationdependent information, which is published in a separate
Users' Note for each implementation (see Section
3.4).
1.5 Precision of the Library
The NAG Fortran Library is developed in
both single precision and
double precision versions. REAL variables and arrays in the single precision version are replaced by DOUBLE PRECISION variables and arrays
in the double precision version.
On most systems only one precision of the Library is available; the precision chosen is that which is considered most suitable
in general for numerical computation (double precision on most systems).
On some systems both precisions are provided: in this case, the double precision routines have names ending in ‘F’ (or ‘A’)
(as in the documentation), and the single precision routines have names ending in ‘E’ (or ‘B’). Thus in Linux 32bit implementations:
 D01AJF is a routine in the double precision implementation;
 D01AJE is the corresponding routine in the single precision implementation.
Whatever the precision, INTEGER variables (and elements of arrays) always occupy one numeric storage unit, that is the Library
is
not implemented using nonstandard integer storage (see
ANSI (1978)), e.g., INTEGER*2.
1.6 Library Identification
You must know
which implementation,
which precision and
which Mark of the Library you are using or intend to use.
To find out which implementation, precision and Mark of the Library is available at your site, you can run a program which
calls the NAG Library routine
A00AAF (or A00AAE in most single precision implementations).
This routine has no parameters; it simply outputs text to the standard output (see Section
2.4).
An example of the output is:
*** Start of NAG Library implementation details ***
Implementation title: Sun(SPARC) Solaris
Precision: double
Product Code: FLSOL21DA
Mark: 21
*** End of NAG Library implementation details ***
(The product code can be ignored, except possibly when communicating with NAG; see Section
4.)
1.7 Fortran Language Standards
All routines in the Library conform to the ISO Fortran 95 Standard (
ISO (1997)), except for the use of a double precision complex data type (usually COMPLEX*16) in some routines in Fortran 77 compiled
double precision implementations of the Library – there is no provision for this data type in the old ANSI Standard Fortran
77 (
ANSI (1978)).
Many of the routines in the Library were originally written to conform to the earlier Fortran 66 standard (
ANSI (1966)), and their calling sequences may contain a few parameters which are not strictly necessary in Fortran 77.
2 Using the Library
2.1 General Advice
A NAG Fortran Library routine cannot be guaranteed to return meaningful results irrespective of the data supplied to it. Care and thought must be exercised in:
 formulating the problem;
 programming the use of library routines;
 assessing the significance of the results.
The Foreword to the Manual provides some further discussion of points (a) and (c); the remainder of Section
2 is concerned with (b).
2.2 Programming Advice
The NAG Fortran Library and its documentation are designed on the assumption that you know how to write a calling program
in Fortran.
When programming a call to a routine, read the routine document carefully, especially the description of the
Parameters. This states clearly which parameters must have values assigned to them on entry to the routine, and which return useful
values on exit. See Section
3.3 for further guidance.
The most common types of programming error in using the Library are:
 incorrect parameters in a call to a Library routine;
 calling a double precision implementation of the Library from a single precision program, or viceversa.
Therefore if a call to a Library routine results in an unexpected error message from the system (or possibly from within the
Library), check the following:
 Has the NAG routine been called with the correct number of parameters?
 Do the parameters all have the correct type?
 Have all array parameters been dimensioned correctly?
 Is your program in the same precision as the NAG Library routines to which your program is being linked?
 Have NAG routine names been modified – if necessary – as described in Sections 1.5 and 2.5?
Avoid the use of NAGtype names for your own program units or COMMON blocks: in general, do not use names which contain a
threecharacter NAG chapter name embedded in them; they may clash with the names of an auxiliary routine or COMMON block used
by the NAG Library.
2.3 Error Handling and the Parameter IFAIL
NAG Fortran Library routines may detect various kinds of error, failure or warning conditions. Such conditions are handled
in a systematic way by the Library. They fall roughly into three classes:
 an invalid value of a parameter on entry to a routine;
 a numerical failure during computation (e.g., approximate singularity of a matrix, failure of an iteration to converge);
 a warning that, although the computation has been completed, the results cannot be guaranteed to be completely reliable.
All three classes are handled in the same way by the Library, and are all referred to here simply as ‘errors’.
The errorhandling mechanism uses the parameter IFAIL, which occurs as the last parameter in the calling sequence of most NAG Library routines. IFAIL serves two purposes:
 it allows users to specify what action a Library routine should take if it detects an error;
 it reports the outcome of a call to a Library routine, either ‘success’ (IFAIL=0) or ‘failure’ (IFAIL≠0, with different values indicating different reasons for the failure, as explained in Section 6 of the routine documents).
For the first purpose IFAIL must be assigned a value before calling the routine; since IFAIL is reset by the routine, it must be passed as a variable, not as an integer constant. Allowed values on entry are:
 IFAIL=0: an error message is output, and execution is terminated (‘hard failure’);
 IFAIL=+1: execution continues without any error message;
 IFAIL=1: an error message is output, and execution continues.
The settings IFAIL=±1 are referred to as ‘soft failure’.
The safest choice is to set IFAIL to 0, but this is not always convenient: some routines return useful results even though a failure (in some cases merely
a warning) is indicated. However, if IFAIL is set to ±1 on entry, it is essential for the program to test its value on exit from the routine, and to take appropriate action.
The specification of IFAIL in Section 5 of a routine document suggests a suitable setting of IFAIL for that routine.
For a full description of the errorhandling mechanism, see the
P01 Chapter Introduction.
Routines in Chapters
F07 and
F08 do
not use the usual error handling mechanism; in order to preserve complete compatibility with LAPACK software, they have a diagnostic
output parameter INFO which need not be set before entry. See the relevant Chapter Introduction for further details.
Some routines in Chapter
F06 output an error message if an illegal input parameter is detected, then terminate program execution immediately. See the
F06 Chapter Introduction for further details.
2.4 Input/output in the Library
Most NAG Library routines perform no output to an external file, except possibly to output an error message. All error messages
are written to a logical
error message unit. This unit number (which is set by default to 6 in most implementations) can be changed by calling the Library routine
X04AAF.
Some NAG Library routines may optionally output their final results, or intermediate results to monitor the course of computation.
In general, output other than error messages is written to a logical
advisory message unit. This unit number (which is also set by default to 6 in most implementations) can be changed by calling the Library
routine
X04ABF. Although it is logically distinct from the error message unit, in practice the two unit numbers may be the same. A few
routines in Chapter
E04 allow this unit number to be specified directly as an option.
All output from the Library is formatted.
There are only a few Library routines which perform input from an external file. These examples occur in Chapters
E04 and
H. The unit number of the external file is a parameter to the routine, and all input is formatted.
You must ensure that the relevant Fortran unit numbers are associated with the desired external files, either by an OPEN statement
in your calling program, or by operating system commands.
2.5 Auxiliary Routines
In addition to those Library routines which are documented and are intended to be called by users, the Library also contains
many auxiliary routines. Details of all the auxiliary routines which are called directly or indirectly by any documented
NAG Library routine are supplied to sites in machinereadable form with the Library software.
In general, you need not be concerned with them at all, although you may be made aware of their existence if, for example,
you examine a memory map of an executable program which calls NAG routines. The only exception is that when calling some
NAG Library routines you may be required or allowed to supply the name of an auxiliary routine from the NAG Library as an
external procedure parameter. The routine documents give the necessary details. In such cases, you only need to supply the
name of the routine; you never need to know details of its parameter list.
NAG auxiliary routines have names which are similar to the name of the documented routine(s) to which they are related, but
with last letter ‘Z’, ‘Y’, and so on, e.g.,
 D01BAZ is an auxiliary routine called by D01BAF.
In a single precision implementation in which the names of documented routines end in ‘E’, the names of auxiliary routines
have their first three and last three characters interchanged, e.g.,
 BAZD01 is an auxiliary routine (corresponding to D01BAZ) called by D01BAE.
A few chapters contain auxiliary routines whose names are obtained by adding 50 to the second and third characters of the
chapter name. For instance, Chapter
E04 has an auxiliary routine with the name E54UCZ.
2.6 Dynamic Memory Application
Some NAG Library routines perform dynamic memory allocation to simplify their interfaces. This is particularly true of routines
(not LAPACK, Chapters
F07 and
F08) added since Mark 21 of the Library. The mechanism used for dynamic memory allocation is implementationdependent, e.g.,
those using a Fortran 90 or Fortran 95 compiler will use the ALLOCATE features of those languages. Where possible, the amount
of memory allocated by a routine will be given in the routine document (usually as a function of routine parameters).
In the case where a routine detects a failure to dynamically allocate sufficient memory, the routine will usually set an error
condition and return a fixed value through the
IFAIL parameter; this value will be the same across all routines, please refer to the
Users' Note for details of the value used for your implementation.
2.7 Thread Safety
Some implementations of the Library facilitate the use of threads; that is, you can call routines from the Library from within
a multithreaded application. Fully thread safe libraries are provided for several platforms — for more information please
contact your local Response Centre (see Section
4). See the
Thread Safety document for more detailed guidance on using the Library in a multithreaded context. You may also need to refer to the
Users' Note for details of whether your implementation of the Library has been compiled in a manner that facilitates the use of threads.
Note that in some implementations, the Library is linked with one or more vendor libraries to provide, for example, efficient
BLAS routines. NAG cannot guarantee that any such vendor library is thread safe.
2.8 Calling the Library from Other Languages
In general the NAG Fortran Library can be called from other computer languages (such as C and Visual Basic) provided that
appropriate mappings exist between their data types.
NAG has produced C Header Files which comprise of a set of header files indicating the match between C and Fortran data types
for various compilers, documentation and examples. The documentation and examples are available from the NAG Web sites (see
Section
4).
The Dynamic Link Library (DLL) version can be called in a straightforward manner from a number of languages and environments,
e.g., Visual Basic, Visual Basic for Applications (Excel), Delphi, C and C++. Guidance on this is provided as part of NAG
Fortran Library DLLs. Further details can be found on the NAG Web sites.
3 Using the Documentation
3.1 Using the Manual
The Manual is designed to serve the following routines:
 to give background information about different areas of numerical and statistical computation;
 to advise on the choice of the most suitable NAG Library routine or routines to solve a particular problem;
 to give all the information needed to call a NAG Library routine correctly from a Fortran program, and to assess the results.
At the beginning of the Manual are some general introductory documents which provide some background and additional information.
The
Library Contents (a structured list of routines in the Library, by chapter) may help you to find the chapter, and possibly the routine, which
you need to solve your problem. Online documentation provides you with a fully linked HTML
Keyword Index (a keyword index to chapters and routines) and
GAMS Classification Index (a list of NAG routines classified according to the GAMS scheme).
Having found a likely chapter or routine, you should read the corresponding Chapter Introduction, which gives background information about that area of numerical computation, and recommendations on the choice of a routine,
including indexes, tables or decision trees.
When you have chosen a routine, you must consult the routine document. Each routine document is essentially selfcontained (it may, however, contain references to related documents). It includes
a description of the method, detailed specifications of each parameter, explanations of each error exit, remarks on accuracy,
and (in most cases) an example program to illustrate the use of the routine.
3.2 Structure of Routine Documents
All routine documents have the same structure, consisting of nine numbered sections:
1. 
Purpose 
2. 
Specification 
3. 
Description 
4. 
References 
5. 
Parameters (see Section 3.3 below)

6. 
Error Indicators and Warnings 
7. 
Accuracy 
8. 
Further Comments 
9. 
Example (see Section 3.5 below)

In a few documents (notably Chapter
E04) there are a further three sections:
10. 
Algorithmic Details 
11. 
Optional Parameters 
12. 
Description of Monitoring Information 
3.3 Specification of Parameters
Section 5 of each routine document contains the specification of the parameters, in the order of their appearance in the parameter
list.
3.3.1 Classification of parameters
Parameters are classified as follows.
Input: you must assign values to these parameters on or before entry to the routine, and these values are unchanged on exit from
the routine.
Output: you need not assign values to these parameters on or before entry to the routine; the routine may assign values to them.
Input/Output: you must assign values to these parameters on or before entry to the routine, and the routine may then change these values.
Workspace: array parameters which are used as workspace by the routine. You must supply arrays of the correct type and dimension.
In general, you need not be concerned with their contents.
Communication Array: array parameters which are used to communicate data from one subroutine call to another.
External Procedure: a subroutine or routine which must be supplied (e.g., to evaluate an integrand or to print intermediate output). Usually
it must be supplied as part of your calling program, in which case its specification includes full details of its parameter
list and specifications of its parameters (all enclosed in a box). Its parameters are classified in the same way as those
of the Library routine, but because you must write the procedure rather than call it, the significance of the classification
is different.
 Input: values may be supplied on entry, which your procedure must not change.
 Output: you may or must assign values to these parameters before exit from your procedure.
 Input/Output: values may be supplied on entry, and you may or must assign values to them before exit from your procedure.
Occasionally, as mentioned in Section
2.5, the procedure can be supplied from the NAG Library, and then you only need to know its name.
User Workspace: array parameters which are passed by the Library routine to an external procedure parameter. They are not used by the routine,
but you may use them to pass information between your calling program and the external procedure.
Dummy: a simple variable which is not used by the routine. A variable or constant of the correct type must be supplied, but its
value need not be set. (A dummy parameter is usually a parameter which was required by an earlier version of the routine and
is retained in the parameter list for compatibility.)
3.3.2 Constraints and suggested values
The word ‘Constraint:’ or ‘Constraints:’ in the specification of an Input parameter introduces a statement of the range of valid values for that parameter, e.g.,
If the routine is called with an invalid value for the parameter
(e.g.,
N = 0), the routine will usually take an error exit, returning a nonzero value of
IFAIL (see Section
2.3).
In newer routine documents, constraints on parameters of type CHARACTER only list upper case alphabetic characters, e.g.,
In practice, all routines with CHARACTER parameters will permit the use of lower case characters.
The phrase ‘Suggested Value:’ introduces a suggestion for a reasonable initial setting for an Input parameter (e.g., accuracy or maximum number of iterations) in case you are unsure what value to use; you should be prepared
to use a different setting if the suggested value turns out to be unsuitable for your problem.
3.3.3 Array parameters
Most array parameters have dimensions which depend on the size of the problem. In Fortran terminology they have ‘adjustable
dimensions’: the dimensions occurring in their declarations are integer variables which are also parameters of the Library
routine.
For example, a Library routine might have the specification:
SUBROUTINE <name> (M, N, A, B, LDB)
INTEGER M, N, A(N), B(LDB,N), LDB
For a onedimensional array parameter, such as A in this example, the specification would begin
You must ensure that the dimension of the array, as declared in your calling (sub)program, is at least as large as the value
you supply for N. It may be larger, but the routine uses only the first N elements.
For a twodimensional array parameter, such as B in the example, the specification might be
 B(LDB,N) – INTEGER array
 On entry: the m by n matrix B.
and the parameter LDB might be described as follows:
 LDB – INTEGER
 On entry: the first dimension of the array B as declared in the (sub)program from which <name> is called.
 Constraint: LDB ≥ M.
You must supply the first dimension of the array B, as declared in your calling (sub)program, through the parameter LDB, even though the number of
rows actually used by the routine is determined by the parameter M. You must ensure that the first dimension of the array
is at least as large as the value you supply for M. The extra parameter LDB is needed because Fortran does not allow information
about the dimensions of array parameters to be passed automatically to a routine.
You must also ensure that the second dimension of the array, as declared in your calling (sub)program, is at least as large as the value you supply for N. It
may be larger, but the routine uses only the first N columns.
A program to call the hypothetical routine used as an example in this section might include the statements:
INTEGER AA(100), BB(100,50)
LDB = 100
.
.
.
M = 80
N = 20
CALL <name>(M,N,AA,BB,LDB)
Fortran 77 requires that the dimensions which occur in array declarations must be greater than zero. Many NAG routines are
designed so that they can be called with a parameter like N in the above example set to 0 (in which case they would usually
exit immediately without doing anything). If so, the declarations in the Library routine would use the ‘assumed size’ array
dimension, and would be given as
INTEGER M, N, A(*), B(LDB,*), LDB
However, the original declaration of an array in your calling program must always have constant dimensions, greater than or
equal to 1.
Consult an expert or a textbook on Fortran if you have difficulty in calling NAG routines with array parameters.
3.4 Implementationdependent Information
In order to support all implementations of the Library, the Manual has adopted a convention of using bold
italics to distinguish terms which have different interpretations in different implementations.
The most important bold italicised terms are the following; their interpretation depends on whether the implementation is
in single precision or double precision.
double precision 
means REAL or DOUBLE PRECISION 
complex*16 
means COMPLEX or COMPLEX*16 (or equivalent) 
basic precision 
means single precision or double precision 
additional precision 
means double precision or quadruple precision 
Another important bold italicised term is machine precision, which denotes the relative precision to which double precision floatingpoint numbers are stored in the computer, e.g., in an implementation with approximately 16 decimal digits of precision,
machine precision has a value of approximately 10^{16}.
The precise value of
machine precision is given by the routine
X02AJF. Other routines in Chapter
X02 return the values of other implementationdependent constants, such as the overflow threshold, or the largest representable
integer. Refer to the
X02 Chapter Introduction for more details.
The bold italicised term
block size is used only in Chapters
F07 and
F08. It denotes the block size used by block algorithms in these chapters. You only need to be aware of its value when it affects
the amount of workspace to be supplied – see the parameters WORK and LWORK of the relevant routine documents and the Chapter
Introduction.
For each implementation of the Library, a separate
Users' Note is published. This is a short document, revised at each Mark. At most installations it is available in machinereadable
form. It gives any necessary additional information which applies specifically to that implementation, in particular:
 the interpretation of bold italicised terms;
 the values returned by X02 routines;
 the default unit numbers for output (see Section 2.4);
 details of name changes for Library routines (see Sections 1.5 and 2.5).
In Chapters
F06,
F07 and
F08, where alternate routine names are available for BLAS and LAPACK derived routines, the alternate name appears in
bold
italics, for example,
dgetrf, which should be interpreted as either SGETRF (in single precision) or DGETRF (in double precision) in the case of
F07ADF, which handles real matrices. Similarly,
F07ARF for complex matrices uses
zgetrf, which should be interpreted as either CGETRF (in single precision) or ZGETRF (in double precision).
3.5 Example Programs and Results
The example program in Section 9 of each routine document illustrates a simple call of the routine. The programs are designed so that they can
fairly easily be modified, and so serve as the basis for a simple program to solve your problem.
The double precision version of the program is provided and this should compile and execute correctly without modification
for double precision implementations.
For each implementation of the Library, NAG distributes the example programs in machinereadable form, with all necessary
modifications already applied. Many sites make the programs accessible to you in this form. They may also be obtained directly
from the NAG Web site.
Note that the results from running the example programs may not be identical in all implementations, and may not agree exactly
with the results which are printed in the Manual and which were obtained from a double precision implementation (with approximately
16 digits of precision).
The
Users' Note for your implementation will mention any special changes which need to be made to the example programs, and any significant
differences in the results.
3.6 Summary for New Users
If you are unfamiliar with this Library and are thinking of using a routine from it, please follow these instructions:
 read the whole of this Essential Introduction;
 consult the Library Contents list to select an appropriate chapter or routine;
 or search through the Keyword Index, GAMS Classification Index or via an online search facility;
 read the relevant Chapter Introduction;
 choose a routine, and read the routine document. If the routine does not after all meet your needs, return to step (b), (c) or (d);
 read the Users' Note for your implementation;
 consult local documentation, which should be provided by your local support staff, about access to the Library on your computing
system;
 obtain an online copy of the example program for the particular routine of interest and experiment with it.
You should now be in a position to include a call to the routine in a program, and to attempt to compile and run it. You may
of course need to refer back to the relevant documentation in the case of difficulties, for advice on assessment of results,
and so on.
As you become familiar with the Library, some of steps (a) to (h) can be omitted, but it is always essential to:
 be familiar with the Chapter Introduction;
 read the routine document;
 be aware of the Users' Note for your implementation.
4 Support from NAG
(a) Contact with NAG
Queries concerning this library should be directed initially to your local Advisory Service. If you have difficulty in making
contact locally, you can contact
NAG directly.
(b) NAG Response Centres
The NAG Response Centres are available for general enquiries from all users and also for technical queries from users with
Support.
The Response Centres are open during office hours, but contact is possible by fax, email and telephone (answering machine)
at all times. Please see the
Users' Note or the
NAG web sites for contact details.
When contacting one of our Response Centres it helps us to deal with you query quickly if you can quote your NAG user reference
and NAG product code.
(c) NAG Web Site
The NAG web site is an information service providing items of interest to users and prospective users of NAG products and
services. The information is regularly updated and reviewed, and includes implementation availability, descriptions of products,
downloadable software and technical reports. NAG web sites can be accessed at
 http://www.nag.co.uk or
 http://www.nag.com or
 http://www.nagj.co.jp
5 Background to NAG
Various aspects of the design and development of the NAG Library, and NAG's technical policies and organisation are given
in
Ford (1982),
Ford et al. (1979),
Ford and Pool (1984), and
Hague et al. (1982).
6 References
ACM (1960–1976) Collected algorithms from ACM index by subject to algorithms
ANSI (1966) USA standard Fortran Publication X3.9 American National Standards Institute
ANSI (1978) American National Standard Fortran Publication X3.9 American National Standards Institute
ANSI/IEEE POSIX (1995) POSIX Standard Thread Library ANSI/IEEE POSIX 1003.1c:1995
Ford B (1982) Transportable numerical software Lecture Notes in Computer Science 142 128–140 Springer–Verlag
Ford B, Bentley J, Du Croz J J and Hague S J (1979) The NAG Library ‘machine’ Softw. Pract. Exper. 9 (1) 65–72
Ford B and Pool J C T (1984) The evolving NAG Library service Sources and Development of Mathematical Software (ed W Cowell) 375–397 Prentice–Hall
Hague S J, Nugent S M and Ford B (1982) Computerbased documentation for the NAG Library Lecture Notes in Computer Science 142 91–127 Springer–Verlag
ISO (1997) ISO Fortran 95 programming language (ISO/IEC 1539–1:1997)
ISO/IEC (1990) Information technology – Programming Language C Current C Language Standard ISO/IEC 9899:1990
Kernighan B W and Ritchie D M (1988) The C Programming Language (2nd Edition) Prentice–Hall
© The Numerical Algorithms Group Ltd, Oxford, UK. 2004