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You are in Section 2 of 9, Article 2.2 of 2.6, Part 2.2.1 of 2.2.3

2 .. Controlling Execution With Control Structures
       2.2 .. Selection Statements
              2.2.1 .. One-Way Decisions

There are generally three versions of selection statements to cover:

• one-way
• two-way
• multi-way

One-way decision statements do some particular thing or they do nothing. Two-way decision statements do one thing or do another. Multi-way decision statements can do many different things depending on the result of an expression.

One-Way Decisions
One-way decisions are handled with an "if statement" and either do some particular thing or do nothing at all. The decision is based on a logical expression which either evaluates to true or false, a value of 1 or a value of 0, respectively.

It is important to remember that logical expressions always evaluate to a value of true or false; a nonzero value is always true, and a value of zero is always false.

If the logical expression is evaluated to true, then the corresponding statement is executed; if the logical expression evaluates to false, control goes to the next executable statement.

The form of a one-way decision statement is as follows:

if (logical expression) stmtT;

The stmtT can be a simple or compound statement. Simple involves a single statement. Compound involves one or more statements enclosed with curly braces { }. A compound statement is called a block statement.

Example 1: simple statement

int c = 3; . . . if ( c > 0 ) cout << "c = " << c << endl;

Example 2: compound statement

int b = 5; int c = 10; . . . if ( c < 5 ) { b = 2 * b + c; cout << c * c * b << endl; }

For an example of how one-way decision statements can be used in a program, consider the following complete program:

1wayselection.cpp

Another type of selection statement is the two-way decision statement. Read on for more...

Next: Two-Way Decisions

You are in Section 2 of 9, Article 2.2 of 2.6, Part 2.2.1 of 2.2.3

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