100'  NAME--DERIV.
110' 
120'  DESCRIPTION--CALCULATES DERIVATIVE OF FUNCTION FNF AT POINT X = A
130'  PROGRAM SHOWS SUCCESSIVE DIFFERENCE QUOTIENTS FOR VALUES OF
140'  X APPROACHING A FROM THE RIGHT, AND GIVES A GOOD APPROXIMATION
150'  TO THE DERIVATIVE.
160'
170'  SOURCE--UNKNOWN
180'
190'  INSTRUCTIONS--SUPPLY FUNCTION BY: 250 DEF FNF(X) = .......
200'                SUPPLY POINT BY:    360 DATA A
210'
220'
230'  *  *  *  *  *  *   MAIN PROGRAM   *  *  *  *  *  *  *  *  *  *  *
240'
250 DEF FNF(X) = 2^X
260 READ A
270 PRINT "  X","DIFFERENCE QUOTIENT"
280 FOR N = 1 TO 10
290 LET D1 = D
300 LET X = A + (1/2)^N
310 LET D = (FNF(X)-FNF(A))/(X-A)
320 PRINT INT(X*1E4+.5)/1E4, D
330 NEXT N
340 PRINT
350 PRINT "DERIVATIVE = " 2*D-D1
360 DATA 0
370 END