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[Diè]

good morning
Thanks to LitusSaxonicum and PaulLaidler about your help
now my program is running and give very good results
WINAPP
INCLUDE<windows.ins>
DOUBLE PRECISION A,B,somme
CHARACTER*50 s
COMMON A,B,somme,N
INTEGER i,w,N
EXTERNAL TRAP
A=0.0E0
B=0.0E0
somme=0.0E0
N=0
i=winio@('%ca[Calcule une integrale]&')
s='{integral A;B} (X+1)dx=somme'
w=winio@('%ob%eq@%cb&',s,0,0)
w=winio@('&')
i=winio@('%5tl&',1,2,3,4,5)
i=winio@('%ffA=%ta&')
i=winio@('%rf&',A)
i=winio@('%ffB=%ta&')
i=winio@('%rf&',B)
i=winio@('%ffsomme=%ta&')
i=winio@('%rf&',somme)
i=winio@('%ffN=%ta&')
i=winio@('%rd&',N)
i=winio@('%ta%`^12bt[INTEGRATION]',TRAP)
END
FUNCTION F(T)
REAL(SELECTED_REAL_KIND(15,307))T
F=T+1
RETURN
END
REAL FUNCTION TRAP()
INTEGER I,N
COMMON A,B,somme,N
REAL (SELECTED_REAL_KIND(15,307))X,B,A,somme
DX=(B-A)/N
TRAPE=(F(A)+F(B))/2
X=A
DO 10 I=1,N-1
X=X+DX
TRAPE=TRAPE+F(X)
10 CONTINUE
TRAP=TRAPE*DX
somme=TRAP
CALL window_update@(somme)
RETURN
END
your very truly[/img]

[LitusSaxonicum]

I'm a great believer in adding white space. I put in some code to catch the obvious error cases - there may be more. The TRAP function should be an INTEGER FUNCTION. You don't need to use the variable "TRAP" in calculating "somme".