Sharp PC-1403 - Page 93

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of B
N ote: Value of A and B m u s t be 0 (fa l s e) o r 1 (t r ue }.
T r u e
F a lse
T rue
F alse
Tr u e
F alse
True
F alse
Val u e
V a lue o f A
AXOR B
of B
Tru e F als e
T r u e T r ue T rue
False
T r ue
F alse
Va lu e
T r ue
F a l se
Tru e
T r u e
F alse
F a l s e
F a l s e F a l se
Value
of B
Val u e of A
A OR B V al ue of A
AA ND B
R elat i on al expre s s i on s e v a l uate to eit h erTr u e o r F al s e . T h e computer r eprese n ts Tr ue
by a 1 ; False is represe n ted b y a 0 . I n a ny l og i ca l te st , a n e x press i on whi ch evaluat es
to 1 or more will be regar de d a s True , w her e as one wh ic h ev aluates t o O or less will be
con si d ered F alse . Good pr og r amm in g p r ac t i ce, h ow e v e r , d i ctates the use o f a n
expl i c it re l a ti on a l express i on i ns t ead of r e l y i ng o n t h i s co i nc i de n ce .
Logical Expressions
Logical expressions are re l a t i ona l e x press ions wh i ch u se o pera t o r s AND , OR,
XOR, and N OT. AND, OR , and XOR a re u se d to connect two relationa l exp r es-
si on s; the valu es o f the comb i ne d e x p r ess i ons a r e as show n in th e fo l lo wi n g t abl es .
"ABCOEF " = " ABCDEF "
"ABCO E F " <> " ABCDE "
" ABCDEF " > " A B CDE "
A<B
C(1 , 2) > ;: 5
0(3) <> 8
I f A w a s equ a l to 1 O, B equa l t o 12 , C(1 , 2 ) equa l t o 6, a nd 0 ( 3 ) e qua l to 9, all of
these r e l at i o nal e xpr es sio n s wo u l d be T ru e .
C hapte r s trings c a n a l so be compare d i n re l a ti ona l exp ressions. The two s t ring s ar e
compared c h a rac ter b y c ha r ac t er acco rding to t h eir A SC I I val u e s tarti n g at the first
cha r a c ter ( see A ppe ndix B f o r A SC II v al u e s). If one s tring i s s hort e r th a n th e othe r , a
o o r N UL will b e u s e d fo r any mi ss i n g po s it i on s . All o f the followi n g r elat i onal
ex pression s are T r ue :
The follow i ng are va l i d re l a ti on al e xp re ss i o n s :
C on ce p t s and Terms of BASIC