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And Iterative Data Types

A programming language cannot be
a programming language with out its conditional and iterative structures.

Programming languages are built to accomplish the task of controlling computer
input and output. A programmer must use every tool available to complete
his/her given tasks, and conditional as well as iterative statements are
the most basic items of programming which must be mastered. Many
different programming languages can demonstrate conditional and iterative
statements including C++, Java, Pascal, Qbasic, COBOL, and Scheme.

Most of these languages implement conditional and iterative statements
in a similar fashion; however, there are a few differences.

The conditional structure is easy
to understand and self-defining. The whole statement is base on a
condition and its veracity. When the statement or "test" is found
to be true, a statement is executed, and if it is false, another test is
given or the program continues to the next block. Conditional structures
include the simple, two-alternative, multi-alternative, and non-deterministic
conditional. The simple conditional is the easiest to understand
being the IF-THEN statement.
if <Boolean expression> then
<block of statements>

IF a condition is met THEN execute a statement.

The two-alternative conditional or IF-ELSE is also easy to understand.
if <Boolean expression> then
<block of statements>
<block of statements>

IF a condition is met execute a statement;

ELSE the condition was not met so execute a different statement.

The multi-alternative conditional is very close to the two-alternative
if <condition-1> then
elseif <condition-2> then
elseif <condition-n> then
[else <statement-block-(n+1)>]
end if

The IF question is asked about a statement,
and if it is not true, the next statement is examined. If statement
number two is not true, the next statement is examined; then the next statement
is examined and so forth until a condition is met, and the control is carried
out of the multi-alternative conditional. The non-deterministic conditional
is similar to the multi-alternative conditional, because it has multiple
if <condition-1> &#61614;
when <condition-2> &#61614;
when <condition-n> &#61614;
end if

The reason multi-alternative and non-deterministic
conditionals are different, stems from the release of program\'s control
or flow. The non-deterministic conditional tests each statement to
see if its condition is met; whereas the multi-alternative conditional
only tests statements until one of the conditions is met. After one
of the conditions is met, the multi-alternative conditional releases the
program control and fails to check anymore statements.

The iterative structure is a bit
more complicated than the conditional structure, but it is easy to understand.

An iterative structure consists of a block of statements that are executed
repetitively. They might be executed once or a hundred times depending
on the controls placed on the structure. Iterative structures include
non-terminating, pretest, posttest, in-test, fixed-count, and non-deterministic
iteration. The non-terminating iterative structure is not very common,
because once it has program control, it does not release its control until
the whole program is terminated.
end loop

Once a non-terminating iterative structure
is activated it continues to run forever. The pretest iterative structure
tests a condition first, then if it is true, the following statements are
executed repeatedly - testing the statement each loop - until the
statement is false.
while <condition> loop
end loop

Once the statement is found to be false,
control is returned to the program ending the pretest iterative statement.

The posttest iterative statement is the same as the pretest statement except
the condition is tested after the sequence of statements. With the
posttest iterative statement, the programmer is guaranteed to have the
sequence of statements executed at least once. The statements are
executed before the conditional statement has a chance to be tested.

With the in-test iterative statement, the conditional statement is tested
in the middle of the sequence of statements. It can be useful when
it is necessary to run a portion of the statement at least once regardless
of the outcome of the conditional. Fixed-count iteration is very
popular, because it allows a sequence of statements to be executed a finite
number of times instead of relying on a condition to be true or false.

The fixed-count iteration is simply do <sequence-of-statements> x number
of times. The non-deterministic iterative statement is similar to
the non-deterministic conditional statement.
when <condition-1> &#61614;
when <condition-1> &#61614;
when <condition-n> &#61614;
end do

The iterative statement executes until
none of the conditions are found to be true. At that time, control
is release back to the program from the non-deterministic iterative statement.

C++ has every type of control structure
a programmer could ever need, and they are all easy to implement.

The three types of condition statements