Data Processing Definitions

             THE LANGUAGE OF COMPUTER PROFESSIONALS
                       SIMPLY STATED FOR A BEGINNER
                              Compiled and Edited by
                   Dr. Thomas V. Sobczak, FSME, FIAE, FIPE

INTRODUCTION
 
     This glossary, a collection of inputs from dozens of BULLETIN BOARD SYSTEMS
(BBS), provides a concise familiarization with the basic and fundamental terms used by
computer professionals when discussing computers.  You can benefit from this narrative
glossary in two ways - either by reading it all, or by scanning the boldface words for the
terms in which you are interested.  It is organized as follows:

                      COMPUTER MATH FOR NOVICES
                      BASIC COMPUTER CONCEPTS
                      DEFINING DISKS
                      OPERATION SYSTEMS
                      PROGRAMS AND PROGRAMMING LANGUAGE
                      STRUCTURING DATA
                      PARTICIPATING PEOPLE

     You will be introduced to one hundred and eighty-nine (189) terms organized in a
perspective oriented to the non-technical person who has an interest in computing.  

COMPUTER MATH FOR NOVICES
 
Computers only work with BINARY NUMBERS (BASE 2)- numbers made of zeroes and
ones (0's and 1's).  These BINARY DIGITS are called BITS, for short.  No matter what a
computer is doing, it is working with bits.  Even if the subject matter is alphabet characters,
or decimal arithmetic, the method is still binary numbers.
 
Writing many bits, for example 0101010011101010101, is inconvenient, so several
shorthand notations have been developed.  The most common is HEXADECIMAL, or
BASE 16 notation.  Hexadecimal digits have sixteen possible values, from 0 through 15;
they are written as 0 through 9, followed by A (representing the value 10), and B (meaning
eleven), C through F (with a value of fifteen).  Hexadecimal digits, also called HEX,
represent four binary digits, or bits, at a time.  Another system for notation, called OCTAL
(BASE 8), uses the digits 0 through 7 and represents 3 bits at a time.  You are most
familiar with the DECIMAL notation method (BASE 10) used by humans to manipulate
numbers
 
The bits that a computer uses are grouped into larger units.  A group of eight bits is called
a BYTE.  Since hex notation represents four bits at a time, it takes two hex digits to
represent the value stored in a byte ( hex digits are sometimes whimsically called
NIBBLES, or NYBBLES).  A byte can be used to store two to the eighth power of values
- 256 different values.   The values can be interpreted as numbers or as characters (such
as letters of the alphabet).  One byte can hold one CHARACTER, and therefore the terms
bytes and characters are sometimes used interchangeably.  The letters of the alphabet and
the ten digits, together, are called the ALPHANUMERICS, although the term is sometimes
used loosely to mean any text data.
 
When bytes are used to hold characters, some code must be used to determine which
numeric value will represent which character.  The most common code is the American
Standard Code for Information Interchange (ASCII).  In ASCII, the capital letter A has the
value 65 (in hex notation, 41), B is 66, and so forth.  ASCII includes codes for letters,
numbers, punctuation and special control codes.
 
ASCII proper has only 128 different codes, and needs only 7 bits to represent it, but since
ASCII characters are almost always stored inside 8-bit bytes, there is actually room for the
128 ASCII codes, plus another 128 codes.  The other codes are sometimes called
EXTENDED ASCII.  ASCII codes are standardized, but EXTENDED ASCII varies from
computer to computer.
 
Traditionally, IBM computers have not used ASCII coding to represent characters.  Instead,
they use EBCDIC (the Extended Binary Coded Decimal Information Code).  Although
EBCDIC has been very little used in personal computers, it may become more important
to us, as data is transferred more and more between IBM and the rest of the world.
 
ASCII DATA, or an ASCII FILE, is data that consists of text - letters of the alphabet,
punctuation, and so forth - rather than numbers or other data.  Sometimes the term ASCII
is used loosely to mean text data.  Properly speaking, an ASCII file not only contains the
ASCII codes for letters, spaces punctuation and so on, but also contains the standard
ASCII codes for formatting, such as carriage return (go to the start of the next line down
the page/screen) and end-of-file.
 
When a byte is used to represent a number, the 256 different values can be interpreted as
either all positive numbers ranging from 0 through 255, or as positive and negative
numbers, ranging from -128 through 127.  These are referred to as UNSIGNED (0 to 255)
or SIGNED (-128 to 127) numbers.
 
To handle larger numbers, several bytes are used together as a unit, often called a WORD.
For different computers different meanings are given to the term word, but most often it
means either two bytes (16 bits) or four bytes (32 bits).  For the IBM PC family of
computers a word usually means a two-byte, 16-bit number.  Some machines process
using a DOUBLE WORD.  Newer PCs use eight (8) bytes (64 bits).  This is a Quadruple
Word.
 
A two-byte word has two the sixteenth power different possible values.  These can be used
as unsigned numbers, with a range of 0 through 65,535, or signed numbers, with a range
of -32,768 through 32,767.  As processor speeds increase the possible values being
addressed increase in direct proportion.
 
INTEGERS, or whole numbers, are not satisfactory for some tasks.  When fractional
numbers are needed, or a very wide range of numbers is needed, a different form of
computer arithmetic is used.  This is called FLOATING-POINT.  Floating-point numbers
involve a fractional portion, and an exponent portion, similar to the SCIENTIFIC
NOTATION used in engineering.  To work with floating-point numbers, computers interpret
the bits of a word in a special way.  Floating-point numbers generally represent
approximate, inexact values.  Often  more than one format of floating-point numbers is
available, offering different degrees of accuracy.  Common terms for these formats are
SINGLE-PRECISION and DOUBLE-PRECISION.  Floating point numbers are also
sometimes called REAL NUMBERS.
 
Due to the nature of computer arithmetic and notation, items are often numbered starting
with 0 for the first element; this is called ZERO-ORIGIN.  Counting from zero is done
especially when figuring a memory location relative to some starting point.  The starting
point can be called may things, including BASE and ORIGIN.  The relative location is most
often called an OFFSET.  Starting from any base location in memory, the first byte is at
offset 0, and the next byte is at offset 1.
 
BASIC COMPUTER CONCEPTS
 
All of the mechanical and electronic parts of a computer system are called HARDWARE.
The programs which a computer uses are called SOFTWARE.  A program embedded in
a READ ONLY MEMORY (ROM) chip upon a hardware board is called FIRMWARE.
 
The idea of a computer starts with the concept of MEMORY, or STORAGE.  A computer's
memory consists of many locations, each of which has an address and can store a value.
For most computers, including the PC family, each location is a byte; for others, each
location is a word.
 
The addresses and locations are numbers.  The values stored in each location can either
be discovered (READ) or changed (WRITTEN).  When a value is read or written, the
address of the location must be given.
 
Some computers organize their memory storage into large modular units, often called
PAGES.  IBM PC computers do not use pages, but for addressing purposes they divide
their memory into units of 16 bytes, called PARAGRAPHS (a term that was chosen to
suggest a smaller division than a page).  The memory-addressing mechanism for these
computers uses two parts: a SEGMENT VALUE, which points to a paragraph boundary,
and a RELATIVE VALUE, which points to a byte located at some displacement, or offset,
from the segment paragraph.  The two values, segment and displacement, are needed to
specify any complete address; together, they are sometimes called an ADDRESS
VECTOR, or just VECTOR.
 
Amounts of computer memory are frequently referred to in units of 1024, because 1,024
is a round number in binary notation, and almost a round number in decimal notation.  The
value 1,024 is known as K, from the metric kilo - 64K is 64 units of 1,024, or exactly
65,536.
 
When referring to general capacity, K almost always means 1,024 bytes.  However, when
referring to semiconductor chips, K means 1,024 bits.  When magazine articles refer to
16K and 64K chips, they mean 16K bits (equivalent to 2K bytes) or 64K bits (equivalent to
8K bytes).  It can be confusing.
 
A computer has the ability to perform operation on the values stored in its memory.
Examples of these operations are arithmetic (addition and subtraction) and movement from
location to location.  A request for the computer to perform an operation is called an
INSTRUCTION or COMMAND.
 
A series of computer instructions that together perform some work, is called a PROGRAM.
Programs are also called CODE.
 
The part of the computer that interprets programs and performs the instructions is called
the PROCESSOR.  A very small processor, particularly one that fits onto a single computer
chip is called a MICROPROCESSOR.  The development of microprocessors made
personal computers possible.  Properly speaking, a computer is a complete working
machine that includes a processor and other parts; but the processor part of a computer
is sometimes also called a computer.
 
The MEMORY of a computer is used to store both programs and data.  To the memory,
there is no difference between programs and data.  However, to the processor, only those
stored values that represent valid instructions can be a program.  The processor reads and
writes from its memory both to carry out a program and to access the data that the program
uses.
 
To help it carry out its work, a computer may have a small amount of very specialized
memory that does not have addresses.  This specialized memory is referred to as
REGISTERS.  Registers are used to make arithmetic more efficient, or to assist in handling
addresses.
 
Many modern computers, including the PC family, use a push-down STACK to hold status
information.  Data is pushed onto and popped off the top of a stack, on a last-in-first-out
(or LIFO) basis.  APPLE Computer uses a HYPERSTACK, a software created stack within
the operating system.  It is possible for a knowledgeable computer programmer to corrupt
the software stack and cause unapproved actions to occur.  Some people call the resultant
code VIRUS and Trojan Horse programs
 
When a computer uses a common data path to pass data from one part to another, this
path is called a BUS.  Standard PC models have an 8-bit bus; the AT-class of PCs (which
use the 286 microprocessor) use a 16 bit bus, while the 386/486-class of PCs use a 32-bit
bus.  This BUS WIDTH is a partial reflection of the speed and power of a PC.
 
The memory and processor are the internal part of a computer.  There are many external
parts, generally called PERIPHERAL EQUIPMENT or PERIPHERALS.  Most peripherals
must be connected to a computer through some supporting electronic circuitry, called an
ADAPTER.  For a complex peripheral, such as a diskette drive, the adapter will include
some special logical circuitry called a CONTROLLER.  A controller is often a specialized
computer in its own right.
 
Peripherals may be of many kinds, but they fall into a few simple categories.  STORAGE
PERIPHERALS are used to hold programs and data that can be moved into the
computer's internal memory.  Examples of peripheral storage devices are floppy diskettes,
cassette tape recorders, and high capacity hard disks.  (For more on this, see the section,
Defining Disks)
 
Other peripheral equipment is used to communicate with people.  The pieces of equipment
used to communicate between people and computers are usually called TERMINALS.  A
terminal most often consists of a typewriter-style keyboard, and a television-like display
screen, called a CRT (for cathode ray tube).  A printer of some kind may be used instead
of a cathode ray tube (CRT).  A CRT DISPLAY SCREEN is called a MONITOR, or simply
a DISPLAY.  A color display may accept its color signal information in a combined form,
called COMPOSITE, or separated into its red, green and blue components, called RGB.
 
Large computers may have many terminals, but small personal computers usually work
with only one terminal, which may be built right into the computer system.  Having only one
terminal is a large part of what makes a personal computer personal.
 
Other kinds of peripherals, besides storage and terminals, are printers and telephone
connections.  Connection between computers and telephones are referred to by the names
of some of their parts, such as MODEMS and ASYNCHRONOUS ADAPTERS; all of these
terms, in general use, refer to the entire computer-telephone connection, which is generally
called COMMUNICATIONS or TELECOMMUNICATIONS.  The most common format for
communications connections follows a design standard known as RS-232.  The speed, or
data rate, of a communications line is measured in BAUD, which is bits-per- second.
Twenty-four thousand baud is a common speed for personal communications; 24K baud
is about 12,000 characters per second.  On personal computers, a RS-232 connection is
also called SERIAL, since it transmits data one bit at a time.  A PARALLEL connection can
transmit more than one bit at a time.  Computer PRINTERS come in many varieties.  Many
personal computers use an inexpensive DOT-MATRIX PRINTER, which creates its printed
results by writing a series of dots.  LETTER-QUALITY PRINTERS produce results
comparable to good typewriters.  Most letter-quality printers use a print element that is
either a flat disk, called a DAISY-WHEEL, or one that is shaped like a large thimble. 

Two additional kinds of printers are replacing the traditional dot-matrix and daisy-wheel
printers.  One type is the INK-JET PRINTER, which squirts very tiny drops of ink, and
paints its information with these small dots.  Some ink-jets print as crudely as dot-matrix
printers while others print as finely as a typewriter that uses a fabric ribbon.  The other new
printer technology is called LASER PRINTING.  A laser printer is essentially a
computer-driven photocopier, but where a photocopier gets its image from taking a
camera-like picture of something you're copying, a laser printer creates an original image
of what you want to print.  A computer- controlled laser beam paints the image inside the
photocopier, which then prints the image onto paper.
 
An INTERFACE is a connection between any two elements in a computer system.  The
term interface is used both for connections between hardware parts, and software parts,
as well as the human interface.
 
Much of the equipment that can be connected to a computer is generally referred to as
INPUT/OUTPUT EQUIPMENT or I/O.
 
The smallest physical parts that make up a computer may be called CHIPS.  Chips and
other parts are wired together electrically and held mechanically on BOARDS.  If there is
one principal board, it is called the SYSTEM BOARD, or MOTHERBOARD.  Openings for
the addition of more boards are called EXPANSION SLOTS, into which are placed
MEMORY BOARDS, DISK BOARDS, ASYNCHRONOUS COMMUNICATIONS BOARDS
(telephone connections), and other expansion or peripheral boards.
 
A microprocessor interacts with its world through these three means, MEMORY
ACCESSES, INTERRUPTS, and PORTS.  Ports have a port number or PORT ADDRESS,
and are used for passing data to or from peripheral devices.  INTERRUPTS are used to
get the computer's attention.  There are three kinds of interrupts (although all three are
handled in the same way).  An EXTERNAL INTERRUPT is from the outside world (for
example, from a diskette drive).  An INTERNAL INTERRUPT reports some exceptional
logical situation (for example, division by 0).  A SOFTWARE INTERRUPT is a request from
a program for some service to be performed.  A software interrupt is an alternative to using
a program call to activate a subroutine.  Memory accesses are used to read or write from
the computer's memory.

The computer's memory can be of several types.  Ordinary memory, which can be read or
written to, is called  RAM (random access memory).  Memory that contains permanent data
is ROM (read only memory).  Memory can be dedicated to some particular use, for
example, to hold the data that appears on the computers display screen.  If a display
screen uses the computer's memory to hold its information, the it is a MEMORY-MAPPED
display. The newest level of memory chip is the EPROM (electronically programmable read
only memory.

DEFINING DISKS
 
Data written magnetically on a DISK is stored on SECTORS, which can be individually
read from or written to.  Typically, for PC DISK OPERATING SYSTEM (DOS), a sector is
512 bytes.  Sectors are the disk's physical records - the units that are actually read or
written.  A TRACK is the collection of sectors that will fit into one circle on a disk; a typical
disk format has nine sectors in a track.  If there is more than one surface on a disk drive,
then a CYLINDER is all of the tracks that are the same distance from the center.  Sectors
that are in the same cylinder can be read without moving the disk drive's read/write
mechanism.  Moving the read/write heads from one track/cylinder to another is called
SEEKING, and it is relatively slow.  Typically, there are forty or eighty tracks on each
surface of a diskette and several thousand tracks on a hard disk.
 
A disk needs a table of contents for its files.  This is called a DIRECTORY in DOS and a
CATALOG in APPLE and in the original operating system, CP/M (Control Program
Microprocessor).  Some means must be used to keep track of used and unused space
on a disk and with DOS it is done with the FAT (File Allocation Table).  The first sector
of each disk is dedicated to holding the first part of the operating system's start up
program, called the BOOTSTRAP LOADER, or BOOT RECORD.  On each disk there are
four kinds of sectors - boot record, FAT, directory, and data space (where files are stored).
The WINDOWS Operating System is an advanced version of DOS.  The primary
improvement is the use of a mouse (a mobile pointer) to trigger access to a program, file
or instruction.
 
A diskette is flexible, thus it is called a FLOPPY.  A HARD DISK has a rigid platter in place
of the flexible plastic of a floppy; the rigid shape allows more precise data recording, and
thus higher density and more capacity.  IBM calls the hard disks in their personal
computers FIXED DISKS; everyone else calls them hard disks or hard files.  The sort of
hard disks installed on personal computers today use a collection of methods called
Winchester technology, so hard disks are also called WINCHESTER DISKS.
 
There are other sorts of diskettes as well.  Originally the standard-sized diskettes for
personal computers were 5.25 inches across, a new type of diskette, called a
MINI-DISKETTE, is only around 3.5 inches across.  It is small enough to fit into a pocket
and enclosed in a hard shell, so that it's not floppy (even though the magnetic disk inside
is just as flexible as the one inside a 5.25 inch floppy diskette).  Also, advanced technology
has made it possible to pack much more information onto standard-sized diskettes. These
are called HIGH-CAPACITY DISKETTES.  High capacity diskettes hold 1.2 megabytes of
information. Floppy diskettes can be SINGLE SIDED (SS) or DUAL DENSITY (DD), i.e.,
read from both sides.  Dual density is now common to the personal computer.
 
OPERATION SYSTEMS
 
An OPERATING SYSTEM is a program that supervises and controls the operation of a
computer.  Operation systems are complex and consist of many parts.
 
One element of an operating system is its BIOS, or Basic Input Output System.  The
BIOS is responsible for handling the details of input-output operations, including the task
of relating a program's logical records to a peripheral device's physical records.  At the
most detailed level, the BIOS contains routines tailored to the specific requirements of
each peripheral device; these routines are called DRIVERS, or DEVICE HANDLERS. 
Mid-level computers do not have BIOS built-in to their controls.  The function of the BIOS
is provided by specially conceived software.

Usually an operating system is organized into a hierarchy of levels of services.  At the
lowest level, the DEVICE HANDLERS insulate the rest of the operating system from the
details of each device.  At the next level, relating logical data to physical data is performed.
At a higher level, basic services are provided, such as accepting output data from a
program to be placed into a file.
 
Besides device and data handling, an operating system must supervise programs,
including loading them, relocating them (adjusting their internal addresses to correspond
to their exact location in a memory), and recovering from any program errors, through an
ERROR HANDLER.
 
Another element of an operating system is the COMMAND PROCESSOR, which accepts
and acts on commands given by the computer's user.  Commands usually amount to a
request for the execution of some service program.  The command processor is the part
of an operation most people think of as the operating system.  In DOS and WINDOWS,
the COMMAND PROCESSOR is found in the COMMAND.COM program.

PROGRAMS AND PROGRAMMING LANGUAGES
 
Series of computer instructions are called a PROGRAM.  Parts of programs that are
partially self-contained are called SUBROUTINES.  Subroutines are PROCEDURES if they
do only some work.  They are FUNCTIONS if they also result in a value ("open the door"
is analogous to a procedure; "tell me your name" is analogous to a function). Subroutines
are also called SUB-PROGRAMS, and ROUTINES.
 
Many subroutines use PARAMETERS to specify exactly what work is to be done; for
example, a subroutine that computes a square root needs a parameter to specify what
number to use.  Many subroutines will indicate how successful their operation was through
a RETURN CODE.
 
Computers can only execute programs that appear in the detailed form known as
MACHINE LANGUAGE.  However, for convenience, programs can be represented in other
forms.  If the details of a machine-language program are replaced with meaningful symbols
(such as the terms ADD or MOVE), then the programming language is known as
ASSEMBLY LANGUAGE (also called ASSEMBLER, SYMBOLIC ASSEMBLER, or
MACRO-ASSEMBLER). Assembler is called a LOW-LEVEL LANGUAGE, because
assembly programs are written in a form close to machine language.  Other forms of
programming languages are more abstract and produce many machine instructions for
each command written by the programmer.  These are called HIGH-LEVEL LANGUAGES;
examples are BASIC, PASCAL, FORTRAN, COBOL, PL/I, C, ADA, LOGO and FORTH.
 
Programs that translate high-level language programs into a form usable by the computer
are called COMPILERS; for low-level languages, the translators are called ASSEMBLERS.
There is no real difference between a compiler and an assembler - they both translate from
a human programming language to a form of machine language.
 
When a person writes a computer program, the form it takes called SOURCE CODE, or
SOURCE.  When the source code is translated (by an assembler or compiler), the result
is often called OBJECT CODE.  Object code is nearly ready to be used, but has to
undergo a minor transformation, performed by a LINK EDITOR, or LINKER, to produce
a LOAD MODULE which is a finished, ready-to-use program.  An error in a program is
called a BUG, and the process of trying to find errors, or trying to fix them, is called
DEBUGGING.
 
There are usually many ways to accomplish an objective with a computer program.  The
scheme, formula, or method that a program uses is its ALGORITHM.  For many tasks -
even as simple a one as sorting data into alphabetical order - there are dramatic
differences in the efficiency of different algorithms.  The search continues for better and
better methods.
 
A program works with symbolic entities called VARIABLES.  In effect, a variable is the
name of a place that can hold data of some type.  Specific data can be moved into and out
of a variable, and the purpose of the variable is to provide a mechanism for manipulating
data.  Variables usually have a fixed type, which indicates what sort of data it can
accommodate: for example, INTEGER type, SINGLE- AND DOUBLE-PRECISION
FLOATING POINT, and STRING (a collection of text characters).  In a program, a FILE
is just a special kind of variable, one that can be connected to a diskette or some device,
such as the display screen to allow the manipulation of large volumes of data by
establishing chunks which are reasonable for processing by a computing device.
                   
STRUCTURING DATA 
 
Data is organized and viewed differently, depending upon who or what is looking at it.  To
the computer itself, data consists of just bits and bytes.  To programmers who manipulate
data, there are some traditional logical boundaries for data.  A complete collection of
related data is a FILE (as an example, a mailing-list file).  One complete unit of the
information in a file is called a RECORD; in a mailing list file, all of the information
connected with one address would be a record.  Finally, within a record are FIELDS, the
information of one type.  For example, the ZIP code would be one field in an address
record in a mailing-list file.
 
The records that a program reads or writes are LOGICAL RECORDS.  Logical records are
placed in the storage medium's PHYSICAL RECORDS - the pieces actually read or written
to a diskette.  A program sees logical records, while the operating system performs any
necessary translating between logical and physical records.  On a disk, a physical record
may be called a SECTOR, although depending upon the size device many physical records
could be within a sector.
 
The terms DATA BASE and DATA BASE MANAGER are used so widely, that they have
no precise meaning.  When data is large, complex, and spread across several files, it might
be called a data base or a Knowledge base.  A data base manager is a program - usually
large and complex in itself - that can control and organize a data base.  [Full scale data
base management of enormous quantities of information is far beyond the capabilities of
most of today's personal computers. Yet in the future the development of CD or
COMPACT DISK technology will allow newly developed machines to equal today's
mainframe devices ]
 
PARTICIPATING PEOPLE
 
When using a personal computer, one person can do everything that is to be done.
However, in traditional large computer systems there is a division of labor, separating
human involvement with a computer into various roles.  Users of personal computers may
wonder about the meaning of various job titles used.
 
The USER, or END-USER, is the person for whom computer work is done.
 
The SYSTEMS ANALYST, or ANALYST, determines the details of the work that the
end-user needs done, and decides on the general strategy of how a computer will perform
the work.
 
The PROGRAMMER converts the analyst's general strategy into the detailed tactics and
methods to be used.  This usually includes writing (and testing) the actual program.
However, actually writing and testing the program is sometimes left to a CODER.

The coder turns the programmer's detailed methods into the machine comprehensible
instructions.
 
The OPERATOR runs the program on the computer to produce the results needed by the
user.  The KEYPUNCH OPERATOR or DATA ENTRY OPERATOR types the data into the
memory to build the files or DATABASES used during processing.

Some organizations have a SYSTEM ADMINISTRATOR who monitors operations, quality
of work and security.  COMPUTER SECURITY is the act of exercising common sense to
protect one's resources.  Common sense is using a computer security product such as  V-
PHAGE DOS and DOS LAN product

CONCLUSION

While the foregoing is trivia to the more sophisticated /advanced practitioner of the art of
programming it was our thought that a refresher was in order for the universe of people
who simply turn on their PC (Personal Computer) and type "123" or "WP" without ever
knowing the wonders of technology we all take for granted. 
           
Our world is beset by the problems caused by the inability of peers to communicate.  It is
the hope of the Management at TVS Consultants that in a small way we might
contribute to a better understanding among peoples using computers.  We have also
created a DICTIONARY of HACKER and TELEPHONE PHREAKER terms which orient
computer users to the hobbyist terminology being applied in traditional computing.

Finally, Sobczak created the SME Glossary of terms used in Manufacturing.