raphs and sym bols Birthdays program
| S This program uses another way to display information on the screen lt uses symbols to
can program a computer lo presen! informaton inall kinds of |
teren! ways. (Or instance, as Words, numbers, picturesor gra phs compare the number of people who were born in different seasons of the year. You
ni! could use a program like thus to compare, say, sightings of a certain bird in different

plicated informalon can be made much easier to understand ifyou seasons, or the number of wins of different football teams. Before writing a long

strate 1! with graphs, pictures and symbols. program like this it is a good idea to write a program plan.

Program plan
Rim: To compare the number of people with birthdays in winter, spring, summer and

With a computer it is very easy to drawa
graph of the way Y changes in relationto
his can be expressed as an eguation, say X. To plot the graph you need to findthe

aginea peach tree whose yield of fruit
»ases each year in relahonto itsage.

3X42(Y istheyieldand X istheage).lt  valueofY for each value ofX. You cando
hard to grasp what this means, though, this very easily in a program using the
d drawing a graph would help. statement LET Y—3"X--2.

1. Give the computer the data (i.e. the
seasons when the people were born)
fora survey of 20 people.

2. Store the data in the computer.

3. Present the data on the screen.

The program

In this graph the
maximum value
forX is14 and the
maximum value

This isthe grap
for Y<3X12.

5 CLS

5 LET A-0
10 FOR X-l TO 14 for Y is3x144-2. a Empty variables ready to
— | 20 LET Y-3aXt2 a use lor running totals lor
30 PLOT (X,Y) 8 LET D
4% NEXT X 10 FOR
50 END 20 PRINT "PERSON ";1;" WAS BORN IN"
| 30 PRINT "WINTER, SPRING, SUMMER OR AUTUMN" survey
his is the program for drawing this calculate Y andline 30 plots X and Y onthe 40 PRINT "TYPE W, SP, SU OR A"
pap The loop sets X at all the values screen. In graphs programs, you must 50 INPUT B$
om | to 14. Eachtime the loop is make sure the maximum values for Xand 60 IF B$<"W" THEN LET AsAt]l Lines 60 to 100 check the answer
epeated, line 20 uses the value ofX to Y will fit on the screen or you will get a bug. 710 IF B$<"SP" THEN LET B-B4] in B$ and add one to the variable
80 IF B$<"SU" THEN LET C-Ct] lor that season.
90 IF B$-'A" THEN LET DsDtl
omputers and maths 100 NEXT | JN ISTE — Sends computer back to repeat guestion.
n calculations which have several ir LET N<A The subroutine makes ihe computer print a

parts, such as 3X X 2, the computer
ways does the multiplications or

divislons before it adds or subtracts.
lis means that the computer would
Sive the same answer for these two sums:

M——— number ol stars egual to the number in each
120 GOSUB 200 s bi

135 LET NaB

140 GOSUB 200 By putting the total into N each ume, tne

150 PRINT "SUMMER TOTAL"; computer can use the same routine for each
155 LET N-C SRAM.

PRINT 44618 PRINT 84446

160 GOSUB 200 |
Xi you want the computer to do the sum 175 LET N<D
na difierent order you use brackets, re ratan Gi

PRINT STARS Line 210 checks in case no-one was born ina

like this:
! Can you write a program to get the 200 REM: SUBROUTINE TO
: RINT (8--4)46 em dar dar yo (id val koči 0 IF N<0 THEN GOTO 250 TT jh
: number trick? (To find the number you FOR Ii TOR k nj mapo o ambon

au,

Ttus time the computer adds 8 and4, first thought of you subtract 4 fromthe line 230 "N" times.

hen multiplies by 6. result, then divide by 2.)

PETE
EE