100'  NAME--INTGRT
110'
120'  DESCRIPTION--SIMPLE INTEGRATION ROUTINE
130'
140'  SOURCE--UNKNOWN
150'
160'  INSTRUCTIONS--ENTER FUNCTION TO BE COMPUTED AS
170'     270 DEF FNF(X) = ........
180'  LIMITS OF THE INTEGRATION ENTERED AS: 430 DATA A,B
190'  ANSWER COMPUTED TO WITHIN 1E-4 OF RELATIVE ERROR.
200'  THIS IS ABOUT 4-PLACE ACCURACY, THE ACCURACY MAY BE CHANGED
210'  BY CHANGING THE CONSTANT IN LINE 430. E.G.
220'     430 DATA 1E-6    YIELDS 6-PLACE ACCURACY.
230'
240'
250'  *  *  *  *  *  *  *    MAIN PROGRAM   *  *  *  *  *  *  *  *  *  *
260'
270 DEF FNF(X) = X^2+X+1
280 READ A,B,E
290 LET H = B-A
300 LET T = (FNF(A)+FNF(B))*H
310 LET M = 0
320 LET T = (T+M)/2
330 LET M = 0
340 FOR X = A+H/2 TO B STEP H
350    LET M = M + FNF(X)
360 NEXT X
370 LET M = M*H
380 LET S = (T + 2*M)/3
390 LET H = H/2
400 IF ABS(T-M)/ABS(S) > E THEN 320
410 PRINT "INTEGRAL = " S
420 DATA 0,1
430 DATA 1E-4
440 END