HP Fortran Programmer's Guide (B3908-90031; September 2011)

Glossary
position-independent code
Glossary262
position-independent code Object code that
contains no absolute addresses.
Position-independent code (PIC) has linkage tables
that contain pointers to code and data. This table is
filled in by the loader at runtime. Object code that
consists of PIC can be used to create shared
libraries.
precision The number of digits to which
floating-point numbers are represented.
Double-precision numbers can have greater
precision than single-precision numbers.
profilers Programming tools that determine where
a program spends its execution time. Profilers that
come with HP Fortran 90 include prof, gprof,
and CXperf.
R-S
roundoff error The loss of precision that can occur
as a result of floating-point arithmetic. Different
orders of evaluating a floating-point expression can
produce different accumulations of roundoff errors,
which in turn can sometimes cause the expression
to yield significantly different results.
row-major order The method of storing
C-language arrays in memory. (Fortran arrays are
stored in column-major order.) Row-major order
requires the rows of a two-dimensional array to be
in contiguous memory locations. For example,
given the array a[3][4], element a[0][0] would
be stored in the first location, a[0][1] in the
second, a[0][2] in the third, and so on.
segmentation violation A type of exception that
occurs when an executing program attempts to
access memory outside of its allocated memory
segment; also called a memory fault.
serial execution Program execution on only one
processor at a time. See also parallel execution..
shared executable An executable program whose
text segment (that is, its code) can be shared by
multiple processes.
shared library A library of routines that can be
linked to an executable program at runtime and
shared by several programs simultaneously. The
names of shared libraries have the .sl
extension. See also archive library..
side effects A condition that prevents the optimizer
from parallelizing a loop. A procedure that is
called within a loop has side effects if it
communicates with the outside world other than
through a return value.
signal See trap.
stack overflow An error condition that occurs
when the runtime system attempts to allocate more
memory from the stack than is available. This
condition can occur when attempting to allocate
very large arrays or when a recursive program is out
of control.
static variable Variables that are allocated from
static storage (sometimes referred to as the heap).
Static variables have two characteristics of note:
• They preserve their value for the lifetime of the
program.
• They are initialized when they are allocated.
By default, program variables in HP Fortran 90 are
automatic.