SCREEN 12:CLS

 OX=44
 OY=64
 XM=640-2*OX
 YM=480-2*OY
 FO=8
 SV=7
 TE=0

 WINDOW(-OX,-OY)-(XM+OX,YM+OY)
 PAINT(1,1),FO
 PSET(0,0),SV:LINE-(0,YM),SV:LINE-(XM,YM),SV
 LINE-(XM,0),TE:LINE-(0,0),TE
 NX=13
 NY=10
 DX=XM/NX
 DY=YM/NY
 FOR Y=DY TO YM  STEP DY
 PSET(1,Y),SV:LINE-(XM-1,Y),SV
 PSET(1,Y+1),TE:LINE-(XM-1,Y+1),TE
 PSET(1,Y+2),TE:LINE-(XM-2,Y+2),TE
 NEXT Y
 FOR X=DX TO XM STEP DX
 PSET(X,1),TE:LINE-(X,YM-1),TE
 PSET(X-1,1),TE:LINE-(X-1,YM-1),TE
 PSET(X+1,1),SV:LINE-(X+1,YM-1),SV
 NEXT X

PI=4*ATN(1)
YC=YM/2:KY=-120
T=XM:W=2*PI/T
NT=16
XD=T/NT
GR=32
 DEF FNY1(X)=SIN(W*XD*INT(X/XD))
 DEF FNY2(X)=(SIN(W*X))*SGN(SGN(SIN(W*X))+1)
 DEF FNY3(X)=-SGN(-1+SGN(100-X))*SGN(1-SGN(X-200))
rem GOSUB GRAPHIC
rem DIM A(2*GR),B(2*GR)
gosub newline
input"Input number of harmonics (1-100)";gr
gosub newline
inputf:
 gosub newline
 input"Select function (1-16-step sin; 2-plus sin; 3-puls";nf
 if nf<>1 and nf<>2 and nf<>3 then goto inputf
on nf gosub defa,defb,defc
def fny(x)=(ff1)*fny1(x)+(ff2)*fny2(x)+(ff3)*fny3(x)
gosub graphic
dim a(2*gr),b(2*gr)

gosub newline
?" CALCULATING ALL ";GR;" HARMONICS"
GOSUB FURIE
locate 1,1:?"                                                   ":locate 1,1:?"HIT <ENTER> to restore"
wata1:
 if inkey$<>chr$(13) then wata1
locate 1,1:?"                                                ":locate 1,1:?"hit <Enter> - restore"
GOSUB STORE
gosub newline
?"hit <ESC> - to quit"
wata2:
 if inkey$<>chr$(27) then wata2
STOP

GRAPHIC:
 GC=2: rem GRAPHICS COLOR
 AY=YC
 PSET(0,AY)
 FOR X=1 TO XM
 Y=KY*FNY(X)+YC
 LINE -(X,Y),GC
 AY=Y
 NEXT X
RETURN

FURIE:
 locate 1,36:?"DONE -     %"
 U=1
 FOR I=0 TO GR
 A(I+1)=0:B(I+1)=0
 NI=4*GR
 DXI=T/NI
 FOR X=0 TO T STEP DXI
 A(I+1)=A(I+1)+(2/T)*FNY(X)*(COS(I*W*X))*DXI
 B(I+1)=B(I+1)+(2/T)*FNY(X)*(SIN(I*W*X))*DXI
 NEXT X
 REM ?"A(";I;")=";A(I+1)
 REM ?"B(";I;")=";B(I+1)
 P=INT(100*(U/(GR+1))):U=U+1
 LOCATE 1,43:?P
 NEXT I
RETURN

STORE:
 REM CLS
 gosub newline
 locate 1,1:?"NOW RESTORING FUNCTION AT ";GR;" HARMONICS"
 PSET(0,YC)
 FOR X=1 TO XM
 SG=A(1)/2
 FOR I=1 TO GR
 SG=SG+A(I+1)*COS(I*W*X)+B(I+1)*SIN(I*W*X)
 NEXT I
 Y=KY*SG+YC
 LINE -(X,Y),13
 NEXT X
RETURN

NEWLINE:
 locate 1,1:?"                                                                                "
 locate 1,1
 return

defa:
 ff1=1:ff2=0:ff3=0
 return

defb:
 ff1=0:ff2=1:ff3=0
 return

defc:
 ff1=0:ff2=0:ff3=1
 return