EULER (Numerical Version) - HP 48

Introduction
This program gives coordinates for an approximate solution for the differential equation ${\hbox{dy}\over \hbox{dx}}=\hbox{f(x,y\ )}$ using Euler's method.

If you have not used one of the programs posted on this website before, you should read through the information in the Intro to Programming section first.

The Program
Note: The main program, EULN, will call a subprogram, SUB3. Both programs are given below.

<<RCLF 'flags' STO

-19 SF -2 SF

"INITIAL X" ":X:" INPUT

OBJ 'X' STO

"INITIAL Y" ":Y:" INPUT

OBJ 'Y' STO

"STEP SIZE" ":H:" INPUT

OBJ 'H' STO

"# ITERATIONS" :N:"

INPUT OBJ 'N' STO

SUB3 {U V X Y K H N}

PURGE flags STOF 'flags'

PURGE >>

ENTER 'EULN' STO {This stores the program under variable name EULN.}

<<1 N FOR C FUNC

NUM 'K' STO

X H + 'U' STO

H K * Y + 'V' STO

U VV2 X YV2

LINE U 'X' STO

V 'Y' STO NEXT>>

ENTER 'SUB3' STO {This stores the program under the variable name SUB3}

Running the Program

You will need to enter a function f(x,y) into a variable called FUNC before running the program. Follow the instructions in

<<RCLF 'flags' STO
-19 SF -2 SF
"INITIAL X" ":X:" INPUT
OBJ 'X' STO
"INITIAL Y" ":Y:" INPUT
OBJ 'Y' STO
"STEP SIZE" ":H:" INPUT
OBJ 'H' STO
"# ITERATIONS" :N:"
INPUT OBJ 'N' STO
SUB3 {U V X Y K H N}
PURGE flags STOF 'flags'
PURGE >>

ENTER 'EULN' STO	{This stores the program under variable name EULN.}


<<1 N FOR C FUNC
NUM 'K' STO
X H + 'U' STO
H K * Y + 'V' STO
U VV2 X YV2
LINE U 'X' STO
V 'Y' STO NEXT>>

ENTER 'SUB3' STO	{This stores the program under the variable name SUB3}