Page 27 - Compact Numerical Methods For Computers

A starting point 17
Section 1.8 notes some other details of algorithm expression which relate to the
ease of use of the codes.

1.7. GENERAL NOTATION

I have not attempted to avoid re-use of symbols within this work since this would
have required an over-large set of symbols. In fact, I have used greek letters as
little as possible to save my typists’ and typesetters’ effort. However, within
chapters and within a subject area the symbols should be consistent. There follow
some brief general points on notation.
(i) Absolute value is denoted by vertical bars about a quantity, | |.
(ii) The norm of a quantity is denoted by double vertical bars, || ||. The form of
this must be found, where necessary, from the context.
(iii) A closed interval [u, v] comprises all points x such that u < x < v. An open
interval (u, v) comprises all points x such that u < x < v.
(iv) The exponents of decimal numbers will be expressed using the symbol E as in
-5
1·234 * 10 = 1·234E-5
and
2
6·78 * 10 = 678 = 6·78E2.
This notation has already appeared in §1.2.

1.8. SOFTWARE ENGINEERING ISSUES
The development of microcomputer software for users who are not trained in
computer science or related subjects has given rise to user interfaces which are much
more sophisticated and easy to use than were common when the first edition
appeared. Mathematical software has not escaped such developments, but source
code collections have generally required the user to consolidate program units, add
driver and user routines, and compile and run the programs. In my experience, the
lack of convenience implied by this requirement is a major obstacle to users learning
about software published in source code form. In our nonlinear estimation software
(Nash and Walker-Smith 1987), we were careful to include batch command files to
allow for easy consolidation and execution of programs. This philosophy is con-
tinued here, albeit adapted to Turbo Pascal.
1. All driver programs include code (from the fragment in file startup.pas) to
allow the user to specify a file from which the program control input and the
problem data are to be input. We refer to this as a ‘control input file’. It has a
name stored in the global string variable infname, and is referred to by the
global text variable infile. Algorithms which need input get it by read or readln
statements from infile. The input file can be ‘con’, the console keyboard.

WARNING: errors in input control files may cause source code files to be destroyed. I
believe this is a ‘bug’ in Turbo Pascal 3.01a, the version used to develop the codes.