Software Engineering for Students A Programming Approach

10.5 Structure clashes 131
As seen by the breaker, Figure 10.13 shows the data structure diagram for the
intermediate file, and it is straightforward to derive the program structure diagram
(Figure 10.14).
Similarly, Figure 10.15 shows the structure of the intermediate file as seen by the
second program, the builder, and again it is easy to derive the program structure diagram
for program 2, the builder (Figure 10.16).
Thus, by introducing the intermediate file, we have eradicated the structure clash.
There is now a clear correspondence both between the input file and the intermediate
file and between the intermediate file and the output file. You can see that choosing a
suitable intermediate file is a crucial decision.
From the program structure diagrams we can derive the pseudo-code for each of the
two programs:
program 1 (the breaker)
open files
read line
while not end of file do
while not end of line do
extract next word
write word
endwhile
read next line
endwhile
close files
Intermediate
file
*
Word
Figure 10.13 Data structure diagram for the intermediate file (as seen by the breaker)
Process input
produce
intermediate
Process
line
Process
word
Figure 10.14 Program structure diagram for the breaker program
*
*
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