597 lines
22 KiB
Plaintext
597 lines
22 KiB
Plaintext
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
These are the definitions of the terms used within this Standard.
|
|
|
|
address, byte
|
|
An unsigned 16-bit number that locates an 8-bit byte in a
|
|
standard FORTH address space over the range {0..65,535}. It
|
|
may be a native machine address or a representation on a
|
|
virtual machine, locating the addr-th byte within the
|
|
virtual byte address space. Addresses are treated as
|
|
unsigned numbers. See: "arithmetic, two's complement"
|
|
|
|
address, compilation
|
|
The numerical value compiled for a FORTH word definition
|
|
which identifies that definition. The address interpreter
|
|
uses this value to locate the machine code corresponding to
|
|
each definition.
|
|
|
|
address, native machine
|
|
The natural address representation of the host computer.
|
|
|
|
address, parameter field
|
|
The address of the first byte of memory associated with a
|
|
word definition for the storage of compilation addresses (in
|
|
a colon definition), numeric data, text characters, etc.
|
|
|
|
arithmetic, two's complement
|
|
Arithmetic is performed using two's complement integers
|
|
within a field of either 16 or 32 bits as indicated by the
|
|
operation. Addition and subtraction of two's complement
|
|
integers ignore any overflow condition. This allows numbers
|
|
treated as unsigned to produce the same results as if the
|
|
numbers had been treated as signed.
|
|
|
|
block
|
|
The 1024 bytes of data from mass storage which are
|
|
referenced by block numbers in the range {0..the number of
|
|
blocks available -1}. The actual amount of data transferred
|
|
and the translation from block number to device and physical
|
|
record is a function of the implementation. See: "block
|
|
buffer" "mass storage"
|
|
|
|
block buffer
|
|
A 1024-byte memory area where a block is made temporarily
|
|
available for use. Block buffers are uniquely assigned to
|
|
blocks. See: "9.7 Multiprogramming Impact"
|
|
|
|
byte
|
|
An assembly of 8 bits. In reference to memory, it is the
|
|
storage capacity for 8 bits.
|
|
|
|
|
|
|
|
|
|
4
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
character
|
|
A 7-bit number the significance of which is given by the
|
|
ASCII standard. When contained in a larger field, the
|
|
higher order bits are zero. See: "6. REFERENCES"
|
|
|
|
compilation
|
|
The action of converting text words from the input stream
|
|
into an internal form suitable for later execution. When in
|
|
the compile state, the compilation addresses of FORTH words
|
|
are compiled into the dictionary for later execution by the
|
|
address interpreter. Numbers are compiled to be placed on
|
|
the data stack when later executed. Numbers are accepted
|
|
from the input stream unsigned or negatively signed and
|
|
converted using the value of BASE . See: "number" "number
|
|
conversion" "interpreter, text"
|
|
|
|
defining word
|
|
A word that, when executed, creates a new dictionary entry
|
|
in the compilation vocabulary. The new word name is taken
|
|
from the input stream. If the input stream is exhausted
|
|
before the new name is available, an error condition exists.
|
|
Example of defining words are: : CONSTANT CREATE
|
|
|
|
definition
|
|
See: "word definition"
|
|
|
|
dictionary
|
|
A structure of word definitions in computer memory which is
|
|
extensible and grows toward higher memory addresses.
|
|
Entries are organized in vocabularies to aid location by
|
|
name. See: "search order"
|
|
|
|
display
|
|
The process of sending one or more characters to the current
|
|
output device. These characters are typically displayed or
|
|
printed on a terminal. The selection of the current output
|
|
device is system dependent.
|
|
|
|
division, floored
|
|
Integer division in which the remainder carries the sign of
|
|
the divisor or is zero, and the quotient is rounded to its
|
|
arithmetic floor. Note that, except for error conditions,
|
|
n1 n2 SWAP OVER /MOD ROT * + is identical to n1. See:
|
|
"floor, arithmetic"
|
|
Examples:
|
|
dividend divisor remainder quotient
|
|
10 7 3 1
|
|
-10 7 4 -2
|
|
10 -7 -4 -2
|
|
-10 -7 -3 1
|
|
|
|
equivalent execution
|
|
|
|
|
|
|
|
|
|
|
|
5
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
A standard program will produce the same results, exclusive
|
|
of timing dependencies, when given the same inputs on any
|
|
Standard System which has sufficient resources to execute
|
|
the program. Only standard source programs are
|
|
transportable.
|
|
|
|
error condition
|
|
An exceptional condition which requires action by the system
|
|
which may be other than the expected function. Refer to the
|
|
section "10. Error Conditions".
|
|
|
|
false
|
|
A zero number represents the false state of a flag.
|
|
|
|
flag
|
|
A number that may have one of two logical states, false or
|
|
true. See: "false" "true"
|
|
|
|
floor, arithmetic
|
|
If z is any real number, then the floor of z is the greatest
|
|
integer less than or equal to z.
|
|
The floor of +.6 is 0
|
|
The floor of -.4 is -1
|
|
|
|
free field format
|
|
Numbers are converted using the value of BASE and then
|
|
displayed with no leading zeros. A trailing space is
|
|
displayed. The number of characters displayed is the
|
|
minimum number of characters, at least one, to uniquely
|
|
represent the number. See: "number conversion"
|
|
|
|
glossary
|
|
A set of explanations in natural language to describe the
|
|
corresponding computer execution of word definitions.
|
|
|
|
immediate word
|
|
A word which executes when encountered during compilation or
|
|
interpretation. Immediate words handle special cases during
|
|
compilation. See, for example, IF LITERAL ." etc.
|
|
|
|
input stream
|
|
A sequence of characters available to the system, for
|
|
processing by the text interpreter. The input stream
|
|
conventionally may be taken from the current input device
|
|
(via the text input buffer) and mass storage (via a block
|
|
buffer). BLK , >IN , TIB and #TIB specify the input stream.
|
|
Words using or altering BLK , >IN , TIB and #TIB are
|
|
responsible for maintaining and restoring control of the
|
|
input stream.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
6
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
The input stream extends from the offset value of >IN to the
|
|
size of the input stream. If BLK is zero the input stream
|
|
is contained within the area addressed by TIB and is #TIB
|
|
bytes long. If BLK is non-zero the input stream is
|
|
contained within the block buffer specified by BLK and is
|
|
1024 bytes long. See: "11.8 Input Text"
|
|
|
|
interpreter, address
|
|
The machine code instructions, routine or other facilities
|
|
that execute compiled word definitions containing
|
|
compilation addresses.
|
|
|
|
interpreter, text
|
|
The word definitions(s) that repeatedly accepts a word name
|
|
from the input stream, locates the corresponding compilation
|
|
address and starts the address interpreter to execute it.
|
|
Text from the input stream interpreted as a number leaves
|
|
the corresponding value on the data stack. Numbers are
|
|
accepted from the input stream unsigned or negatively signed
|
|
and converted using the value of BASE . See: "number"
|
|
"number conversion"
|
|
|
|
layers
|
|
The grouping of word names of each Standard word set to show
|
|
like characteristics. No implementation requirements are
|
|
implied by this grouping.
|
|
|
|
layer, compiler
|
|
Word definitions which add new procedures to the dictionary
|
|
or which aid compilation by adding compilation addresses or
|
|
data structures to the dictionary.
|
|
|
|
layer, devices
|
|
Word definitions which allow access to mass storage and
|
|
computer peripheral devices.
|
|
|
|
layer, interpreter
|
|
Word definitions which support vocabularies, terminal
|
|
output, and the interpretation of text from the text input
|
|
buffer or a mass storage device by executing the
|
|
corresponding word definitions.
|
|
|
|
layer, nucleus
|
|
Word definitions generally defined in machine code that
|
|
control the execution of the fundamental operations of a
|
|
virtual FORTH machine. This includes the address
|
|
interpreter.
|
|
|
|
load
|
|
Redirection of the text interpreter's input stream to be
|
|
from mass storage. This is the general method for
|
|
compilation of new definitions into the dictionary.
|
|
|
|
mass storage
|
|
|
|
|
|
|
|
7
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
Storage which might reside outside FORTH's address space.
|
|
Mass storage data is made available in the form of 1024-byte
|
|
blocks. A block is accessible within the FORTH address
|
|
space in a block buffer. When a block has been indicated as
|
|
UPDATEed (modified) the block will ultimately be transferred
|
|
to mass storage.
|
|
|
|
number
|
|
When values exist within a larger field, the most-
|
|
significant bits are zero. 16-bit numbers are represented
|
|
in memory by addressing the first of two bytes at
|
|
consecutive addresses. The byte order is unspecified by
|
|
this Standard. Double numbers are represented on the stack
|
|
with the most-significant 16 bits (with sign) most
|
|
accessible. Double numbers are represented in memory by two
|
|
consecutive 16-bit numbers. The address of the least
|
|
significant 16 bits is two greater than the address of the
|
|
most significant 16 bits. The byte order within each 16-bit
|
|
field is unspecified. See: "arithmetic, two's complement"
|
|
"number types" "9.8 Numbers" "11.7 Stack Parameters"
|
|
|
|
number conversion
|
|
Numbers are maintained internally in binary and represented
|
|
externally by using graphic characters within the ASCII
|
|
character set. Conversion between the internal and external
|
|
forms is performed using the current value of BASE to
|
|
determine the digits of a number. A digit has a value
|
|
ranging from zero to the value of BASE-1. The digit with
|
|
the value zero is represented by the ASCII character "0"
|
|
(position 3/0 with the decimal equivalent of 48). This
|
|
representation of digits proceeds through the ASCII
|
|
character set to the character "(" corresponding to the
|
|
decimal value 9. For digits with a value exceeding 9, the
|
|
ASCII graphic characters beginning with the character "A"
|
|
(position 4/1 with the decimal equivalent 65) corresponding
|
|
to the decimal value 10 are used. This sequence then
|
|
continues up to and including the digit with the decimal
|
|
value 71 which is represented by the ASCII character "~"
|
|
(position 7/14 with a decimal equivalent 126). A negative
|
|
number may be represented by preceding the digits with a
|
|
single leading minus sign, the character "-".
|
|
|
|
number types
|
|
All number types consist of some number of bits. These bits
|
|
are either arbitrary or are weighted.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
8
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
Signed and unsigned numbers use weighted bits. Weighted
|
|
bits within a number have a value of a power of two
|
|
beginning with the rightmost (least-significant) bit having
|
|
the value of two to the zero power. This weighting
|
|
continues to the leftmost bit increasing the power by one
|
|
for each bit. For an unsigned number this weighting pattern
|
|
includes the leftmost bit; thus, for an unsigned 16-bit
|
|
number the weight of the leftmost bit is 32,768. For a
|
|
signed number this weighting pattern includes the leftmost
|
|
bit but the weight of the leftmost bit is negated; thus, for
|
|
a signed 16-bit number the weight of the leftmost bit is
|
|
-32,768. This weighting pattern for signed numbers is
|
|
called two's complement notation.
|
|
|
|
Unspecified weighted numbers are either unsigned numbers or
|
|
signed numbers; program context determines whether the
|
|
number is signed or unsigned. See: "11.7 Stack Parameters"
|
|
|
|
pictured numeric output
|
|
The use of numeric output definitions which convert
|
|
numerical values into text strings. These definitions are
|
|
used in a sequence which resembles a symbolic 'picture' of
|
|
the desired text format. Conversion proceeds from least-
|
|
significant digit to most-significant digit, and converted
|
|
characters are stored from higher memory addresses to lower.
|
|
|
|
program
|
|
A complete specification of execution to achieve a specific
|
|
function (application task) expressed in FORTH source code
|
|
form.
|
|
|
|
receive
|
|
The process of obtaining one character from the current
|
|
input device. The selection of the current input device is
|
|
system dependent.
|
|
|
|
recursion
|
|
The process of self-reference, either directly or
|
|
indirectly.
|
|
|
|
return
|
|
The means of indicating the end of text by striking a key on
|
|
an input device. The key used is system dependent. This
|
|
key is typically called "RETURN", "CARRIAGE RETURN", or
|
|
"ENTER".
|
|
|
|
screen
|
|
Textual data arranged for editing. By convention, a screen
|
|
consists of 16 lines (numbered 0 through 15) of 64
|
|
characters each. Screens usually contain program source
|
|
text, but may be used to view mass storage data. The first
|
|
byte of a screen occupies the first byte of a mass storage
|
|
block, which is the beginning point for text interpretation
|
|
during a load.
|
|
|
|
|
|
|
|
9
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
search order
|
|
A specification of the order in which selected vocabularies
|
|
in the dictionary are searched. Execution of a vocabulary
|
|
makes it the first vocabulary in the search order. The
|
|
dictionary is searched whenever a word is to be located by
|
|
its name. This order applies to all dictionary searches
|
|
unless otherwise noted. The search order begins with the
|
|
last vocabulary executed and ends with FORTH , unless
|
|
altered in a system dependent manner.
|
|
|
|
source definition
|
|
Text consisting of word names suitable for compilation or
|
|
execution by the text interpreter. Such text is usually
|
|
arranged in screens and maintained on a mass storage device.
|
|
|
|
stack, data
|
|
A last in, first out list consisting of 16-bit binary
|
|
values. This stack is primarily used to hold intermediate
|
|
values during execution of word definitions. Stack values
|
|
may represent numbers, characters, addresses, boolean
|
|
values, etc.
|
|
|
|
When the name 'stack' is used alone, it implies the data
|
|
stack.
|
|
|
|
stack, return
|
|
A last in, first out list which contains the addresses of
|
|
word definitions whose execution has not been completed by
|
|
the address interpreter. As a word definition passes
|
|
control to another definition, the return point is placed on
|
|
the return stack.
|
|
|
|
The return stack may cautiously be used for other values.
|
|
|
|
string, counted
|
|
A sequence of consecutive 8-bit bytes located in memory by
|
|
their low memory address. The byte at this address contains
|
|
a count {0..255} of the number of bytes following which are
|
|
part of the string. The count does not include the count
|
|
byte itself. Counted strings usually contain ASCII
|
|
characters.
|
|
|
|
string, text
|
|
A sequence of consecutive 8-bit bytes located in memory by
|
|
their low memory address and length in bytes. Strings
|
|
usually, but not exclusively, contain ASCII characters.
|
|
When the term 'string' is used alone or in conjunction with
|
|
other words it refers to text strings.
|
|
|
|
structure, control
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
10
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
A group of FORTH words which when executed alter the
|
|
execution sequence. The group starts and terminates with
|
|
compiler words. Examples of control structures: DO ...
|
|
LOOP DO ... +LOOP BEGIN ... WHILE ... REPEAT BEGIN ...
|
|
UNTIL IF ... THEN IF ... ELSE ... THEN See: "9.9 Control
|
|
Structures"
|
|
|
|
transportability
|
|
This term indicates that equivalent execution results when a
|
|
program is executed on other than the system on which it was
|
|
created. See: "equivalent execution"
|
|
|
|
true
|
|
A non-zero value represents the true state of a flag. Any
|
|
non-zero value will be accepted by a standard word as
|
|
'true'; all standard words return a 16-bit value with all
|
|
bits set to one when returning a 'true' flag.
|
|
|
|
user area
|
|
An area in memory which contains the storage for user
|
|
variable.
|
|
|
|
variable, user
|
|
A variable whose data storage area is usually located in the
|
|
user area. Some system variables are maintained in the user
|
|
area so that the words may be re-entrant to different users.
|
|
|
|
vocabulary
|
|
An ordered list of word definitions. Vocabularies are an
|
|
advantage in separating different word definitions that may
|
|
have the same name. More than one definition with the same
|
|
name can exist in one vocabulary. The latter is called a
|
|
redefinition. The most recently created redefinition will
|
|
be found when the vocabulary is searched.
|
|
|
|
vocabulary, compilation
|
|
The vocabulary into which new word definitions are appended.
|
|
|
|
word
|
|
A sequence of characters terminated by one blank or the end
|
|
of the input stream. Leading blanks are ignored. Words are
|
|
usually obtained via the input stream.
|
|
|
|
word definition
|
|
A named FORTH execution procedure compiled into the
|
|
dictionary. Its execution may be defined in terms of
|
|
machine code, as a sequence of compilation address, or other
|
|
compiled words.
|
|
|
|
word name
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
11
|
|
|
|
|
|
|
|
|
|
|
|
5. DEFINITIONS OF TERMS
|
|
|
|
|
|
The name of a word definition. Word names are limited to 31
|
|
characters and may not contain an ASCII space. If two
|
|
definitions have different word names in the same vocabulary
|
|
they must be uniquely findable when this vocabulary is
|
|
searched. See: "vocabulary" "9.5.3 EXPECT"
|
|
|
|
word set
|
|
A named group of FORTH word definitions in the Standard.
|
|
|
|
word set, assembler extension
|
|
Additional words which facilitate programming in the native
|
|
machine language of the computer which are by nature system
|
|
dependent.
|
|
|
|
word set, double number extension
|
|
Additional words which facilitate manipulation of 32-bit
|
|
numbers.
|
|
|
|
word set, required
|
|
The minimum words needed to compile and execute Standard
|
|
Programs.
|
|
|
|
word set, system extension
|
|
Additional words which facilitate the access to internal
|
|
system characteristics.
|
|
|
|
word, standard
|
|
A named FORTH procedure definition, in the Required word set
|
|
or any extension word sets, formally reviewed and accepted
|
|
by the Standards Team.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
12
|
|
|