The Rainbow Vol. 10 No. 11 - June 1991.pdf - TRS-80 Color ...

on psect can u e ymbolic name defined
in an th r psect.
T make thi proce ea ier to implement,
the a embler gi e you the ability to
declare your ym olic name a either lo al
or glo al name . Local name are defined
only in their psect and are unknown to
ther psects. In fact,
th r psect rna u
th arne name for
different value
without an "multiply
defined ymb 1 '
conflict .
1 bal . ymb Is
are made available to
all psect , but they
are ref err d to only if
the psect has n t
defin d the arne
name. If one psect
d fin th ymbol
buffer a a global
symb I and a second
defin buffer a a
lo al ymb I. the
.-ymbol in th . e nd
psect i I al and
ifferent fr m th
gl bal . ymb I of the
Off et
0. 5
2. S
4,S
6. 5
8,S
10,5
Type
BOOLEAN
BY
I TEGER
REAL
STRING
I name when it i
mb I w 1 1 ym-
ing Multiple psect
Dir t your attenti n to the ource c de
in 1i tings , 4 and 5. The e three psect
when linked together, form a program that
wait for a k ypre from the keyboardt
44 THE RAINBOW June 1991
dump the alue o the 6 09 r gi, ters to the
creen, and print the A CII valu , in d cimal
of the key p!i d. ach li ling is a
cparate ftle and i embled separately
from the ther .
otice that each psect ha a ymbol
named buffer that lab I a non direct-page
ize De cription
return addres - don t change it
number of parameter pa ed
pointer to fir t parameter
ize, in byte • of first parameter
pointer to econd parameter
ize, in byte of e nd parameter
Figure 1: A Sample Data Block
ize omments
1 byte
1 byte
FF = true 0 = fal. e
2 byte if left-m t bit set, numb r i negati e
5 byte 8-bit exp nent t-bit manti a. I ign bit
varie terminated with FF if le than max ize
Figure 2: The Fh'e Basic Uata Types
variable. he e thr e ymb I are all 1 cal
to their psect and, thus, have different
valu .
here are three gl bal ymb 1 in thi ·
gr up fpsect :Dec RegDump and Divide.
There i · a) ·o only one mainline psectrna
1 n. tice thatthe ther psect dire tive
pe ify the f)pelan 7 , atrrev, edition and
entry ytes as z r .
ariable name that ha e been declared
as global ymb I can b a e: :ed fTom
other psect. simply by u ing that ym I
nam in y ur ur e de. Keep in mind
that th as mbl r pass s only unresol ed
reference t the linker o if th cod in a
psectdefine a ym ol with the arne name
as a global ·ymbol, the global symbol i: n t
u ed.
To acce a global variable from another
psect, us one ofth f llowing methods. If
the ariable i a n n direct-pag varia le
ace them in the normal manner:
leay IObuf.u
ldx counter.u
If a glo al direct-page variable i to
acce ed, precede the variable name with
the le -than ym ol (