Sinclair QL User Manual

•
All these are binary decisions. The first two examples are simple either something
happens or
it does not. The third is a general binary decision with two distinct possible
courses of acfion, both of which must be defined.
You can omit THEN in the long forms if you wish. In the short form you can substitute
:
for THEN.
Consider a more complex example
In which it seems natural to nest binary decIsions. EXAMPLE
ThiS type of nesting can be confusing and you should only do It If it seems the most
natural thing
to do. Careful attention to layout particularly indenting, is espeCially Important.
Analyse a piece of text to count the number of vowels, consonants and other characters.
Ignore spaces. For simplicity the
text is all upper case.
"COMPUTER HISTORY WAS MADE IN 1984" Data
ProgramStructure
•
•
Read in the data
FOR each character:
IF letter THEN
IF
vowel
increase vowel count
ELSE
increase consonant count
END IF
ELSE
IF not space THEN increase other count
END IF
END FOR
PRINT results
100 REMark Character Counts
110 RESTORE 290
120 READ text$
130 LET voweLs = 0: cons =0 : others =0
140 FOR nurn =1 TO LEN (text [)
150 LET ch$ = text$(nurn)
160 IF ch$ >= "A" AND ch$ <= liZ"
170 IF ch$ INSTR "AEIOU"
180 LET voweLs = voweL +
190 ELSE
200 LET cons = cons + 1
210 END IF
220 ELSE
230 IF ch$ <> .. II THEN others:::: others + 1
240 END IF
250 END FOR nurn
260 PRINT "Vowel count is" ! vowels
270 PRINT "Consonent count i 5
11
! cons
280 PRINT "Other count ;s" ! others
290 DATA "COMPUTER HISTORY WAS MADE IN 1984"
Vowel count is 9
Consonant count is 15
Other count is 4
Where there are three or more possible actions and none is dependant on a previous
choice the natural structure
to use is SElect which enables selection from any number
of possibilities.
A magic snake grows without limit by adding a section
to ItS front. Each section may
be
up to twenty units long and may be a new colour or it may remain the same. Each
new section must grow
in one of the directions North, South East or West. The snake
starts from the centre of the window.
12/84
Design
Program
Output
MULTIPLE
DECISIONS
- SELect
EXAMPLE
83

Sinclair QL Specifications

General

Processor	Motorola 68008
Clock Speed	7.5 MHz
RAM	128 KB (expandable to 640 KB)
ROM	48 KB
Operating System	Sinclair QDOS
Release Year	1984
Storage	Microdrive tape loop
Graphics	256x256 pixels, 8 colors
Ports	RS-232, ROM cartridge
Sound	Beeper (internal speaker)