Radio Shack TRS-80 Model II Reference Manual page 19

Model II TRSDOS
Memory Requirements
TRSDOS
occupies 6.1 tracks on the System diskette (39 ,040 bytes). However,
only a small portion is actually in memory at anyone time. The Supervisor
Program, input/output drivers, and other essentials are always in memory.
Auxiliary code is loaded as needed into an "overlay area".
Memory addresses 0 through 10239
(XO'-X'27FF)
are reserved for the Oper-
ating System. Certain commands, called "high overlays", also use memory
addresses up to
X'2FFF'
(details provided in the Commands section). User
programs must be located above
X'27FF';
and you may want to locate them
above
X'2FFF'
to allow use of the high overlays without loss of your program.
DECIMAL
ADDRESS
a
10240
12288
TOP*
32767 or
65535
SYSTEM AREA
USER AREA (SHARED WITH
TRSDOS "HIGH OVERLAY COMMANDS")
USER AREA UNTOUCHED**
BYTRSDOS
MAYBE
RESERVED BY TRSDOS FOR
SPECIAL PROGRAMMING
Last Memory Address
MEMORY REQUIREMENTS OF TRSDOS
HEX
ADDRESS
X'OOOO'
X'2800'
X'3000'
TOP*
X'7FFF'or
X'FFFF'
Note: The term "user program" applies to any program which is not a part of
TRSDOS.
Therefore
BASIC
is a user program. For memory requirements of
BASIC,
see the
BASIC
Reference Manual.
"'TOP
is a memory protect address set by
TRSDOS. IfTRSDOS
is not protecting
high memory, then
TOP
is the same as "Last Memory Address".
**
Single-drive
COpy
from one diskette to another,
BACKUP
and
FORMAT
use
all user memory.
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