Page 139 - Standard Handbook Of Petroleum & Natural Gas Engineering

124 Mathematics

Pascal Language

Pascal names (of units, variables, array elements, etc.), consisting of an initial
letter followed by letters or digits, may be as long as needed in standard Pascal;
however, in practice, most compilers require that a name be unique within a
certain number of characters. (See Table 1-28 for reserved words which may not
be used as names.)

Data Types (Data structures of all types, predefined and user-defined, must
be declared; see “Statements” for type declaration form.)

Integer-Predefined, scalar (ordered) type with a machine-dependent limit,
predeclared as a constant MAXINT.
Real-Predefined scalar type, decimal, or scientific notation may be used.
Boolean-Predefined logical type, ordered so that false < true.
Char-Predefined character type, ordered by code. (See Table 1-22 for two
common code sets.)
User-defined-See “Statements.”
Data Structures

Constant-Type and value assigned at declaration, and once defined, neither
type nor value may be changed.
Variable-Type assigned at declaration and may not be changed; value assigned
by a numerical or character constant, by input or by an expression.
Array-May have more than one dimension; number of dimensions and type
are assigned at declaration and may not be changed; values are assigned to array
elements (which must be of same type) as they are to variables.
Packed array-Produces more efficient use of memory, but slower program
execution than a regular array.
Record-The elements (fields) may be of different types and may be accessed
at random; fields and their types are assigned at declaration and may not be
changed; field values are assigned as are variable values.
File-Composed of elements (which may be records or other data structures)
of the same type; sequential files only in standard Wirth Pascal; external
(physical) files (for input and output) must be declared with the program
heading (see “Statements”) and internal (temporary) files may be added for use
within the program; all files except INPUT and OUTPUT must be declared in
TYPE and/or VAR sections.
Set-Type must be ordinal; must be processed as whole (cannot be broken
down into elements).

Table 1-28
Pascal Reserved Words
and array begin case const
div do downto else end
file for function got0 if
in label mod nil not
of or packed procedure program
record repeat set then to
type until var while with