1. Apparatus for programming a stored-program controller, in which a control program of the controller, containing function calls and stored in a machine-readable form, is displayed in function-diagram representation on a graphical display device by an operating system of a digital computer, wherein said operating system of the digital computer: (a) searches for the function calls in the control program; (b) writes the function calls found sequentially with the lists of associated input and output parameters into a file; (c) splits the file by allocating the function calls to part sequences of function calls, in which splitting operation, beginning with the last function call, each function call, the output parameter of which does not contribute anything to the formation of an input parameter of a function call already allocated to the respective part sequence, is allocated to a new part sequence; (d) allocates values to a first set of variables which are allocated to the individual function calls, of the graphical representation of the function calls including edge zones on the display device; (e) allocates values to a second set of variables which are also allocated to the individual function calls, in which operation these values establish the normalized horizontal displacement of the function calls on the display device and in each case correspond to the largest of the sums which, for the function call considered in each case, can be formed from the values of the variables of the first set which are allocated to the function calls depending on this function call with respect to parameters; (f) allocates values to a third set of variables which are associated with the part sequences, in which operation the values establish the normalized vertical extension of the graphical representation of the part sequences on the display device and in each case correspond to twice the number of function calls in the respective part sequence plus the number of the input parameters not generated in the respective part sequence itself less the number of the first and last input parameters, generated in the respective part sequence itself, in the parameter lists of the individual function calls in the respective part sequence; (g) allocates values to a fourth set of variables which, in turn, are allocated to the part sequences, in which operation the values establish the normalized vertical displacement of the part sequences on the display device and in each case result from the sum of the values of the variables of the third set which are allocated to the part sequences in the sequence of part sequences.