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Define Storage (Ds); Origin Code (Org); Constant Definition (Dc) - RCA Spectra 70 Training Manual

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A symbol appearing in the NAME field is assigned
the address of the leftmost byte ofthe reserved area.
The Location Counter maybe set to any desired value
with the ORG code. This code sets the location
counter to the value appearing in the operand field .
The operand may be a symbol or an asterisk (incre-
mented or decremented) or a self-defining value;
if
a symbol, then it must have been previously de-
fined in the NAME field. With this tool, areas may
be allocated beginning at any desired location, or
may be re-allocated to accommodate varying for-
mats.
NAME
OPERATION
OPERAND
READIN
DS
80C
The character "C", following the area length 80,
tells the Assembler to allocate 80 consecutive one-
byte fields beginning at the current position of the
location counter.
The statements
NAME
OPERATION
OPERAND
1.
READIN
DS
20F
2. READIN
DS
40 H
allocate the same amount of memory. However, the
first example (20F) instructs the Assembler to ad-
vance the location counter to the next word boundary.
and then allocate 20 fields of four bytes each; where-
as the second example (40H) advances the location
counter to the next even byte address, and then al-
locates 40 fields of two bytes each.
Example (ORG
and
DS
Codes)
Assume a read-in area is allocated for a file that
contains transactions in three different formats. The
maximum size record is 80 characters. We want to
name the area, and to name every field within each
format.
NAME
OPERATION
OPERAND
INAR
DS
80C
ORG
INAR \
NACN
DS
lOC
)
NCOD
DS
2C
(
NDAT
DS
4C
New Account
NCUS
DS
25C
I
Transaction
NADR
DS
30C
)
NTYP
DS
2C
NAMT
DS
7C
18
Example (ORG
and
DS
Codes) Cont'cJ
NAME
OPERATION
OPERAND
ORG
INAR
PACN
DS
lOC
I
PCOD
DS
2C
I
PDAT
DS
4C
Payment
PAMT
DS
7C
1
Transaction
PTYP
DS
2C
RACN
ORG
INARl
RCOD
DS
lOC
RDAT
DS
2C
Receipt
RAMT
DS
4C
Transaction
DS
7C
ORG
INAR+80
Reset Location
Counter to
value after
INAR above
Areas allocated by the DS code are not cleared. The
NAME field may be left blank for areas that must be
allocated but are not referenced directly.
CONSTANTS
The DC (Define Constant) code both allocates mem-
ory for,
and stores the value of a constant. The
value is written in the OPERAND field, and is ex-
pressed in one of three forms, as a character, hex-
adecimal or address constant. The length of each
constant is implied by the value in the operand field.
CHARACTER CONSTANTS
A constant not exceeding 16 characters may be writ-
ten on one statement line. Each character is con-
verted to a byte. The value, enclosed in single quote
marks, is preceded by a C.
NAME
EOF
CaDS
OPERATION
OPERAND
DC
C'END OF RUN'
DC
C
t
OI2AB'
HEXADECIMAL CONSTANTS
A hexadecimal constant must be used in lieu of a
character constant when one or more of the bytes
cannot be expressed by a character value. The
value is written in an even number of hexadecimal
digits not exceeding thirty-two. Each pair of hexa-
decimal digits (starting from the left end of the ex-
pressed value) is used to generate a byte.
OPERATION
OPERAND
DC
X'4020206B20204B202060'
An explanation of the above example is given in DATA
EDITING (page 33).

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