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Unformatted text preview: , could be expressed by using
only the following three simple logic (control) structures:
1. Sequence logic,
2. Selection logic, and
3. Iteration (or looping) logic.
It was found that when programs are structured by using only these three logic structures,
they can be read from top to bottom and are easier to understand. That is, by
conceptualizing the logic of a program in the form of these three logic structures,
programmers can avoid writing spaghetti code and produce programs that are easy to
understand and maintain. It was found that this also helped in reducing program errors
and the time spent in program testing. The use of these three basic control structures
resulted in a more scientific approach to solving a programming problem and was later
termed as structured programming technique.
After realizing the advantages of structured programming technique, many organizations
now impose the use of the three basic logic structures in all their programs. It is generally
advised as good programming practices to develop program logics and write programs
using the three basic logic structures. Hence in the discussion below we will see the
pseudocodes for the three basic logic structures (flowcharts of these logic structures have
also been shown for those who are rhore comfortable with flowcharts).
Sequence logic is used for performing instructions one after another in sequence. Thus,
for sequence logic, pseudocode instructions are written in the order, or sequence, in
which they are to be performed. The logic flow of psuedocode is from the top to the
bottom. Figure 11.14 shows an example of sequence logic structure.
(a) Flowchart Process 1
Figure 11.14. Flowchart and pseudocode for sequence structure.
Selection logic, also known as decision logic, is used for making decisions. It is used for
selecting the proper path out of the two or more alternative paths in the program logic.
Selection logic is depicted as an IF...THEN...ELSE or an IF...THEN or a CASE structure.
The flowcharts of Figures 11.15, 11.16 and 11.17 respective...
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This document was uploaded on 04/07/2014.
- Spring '14