Structure of If-Then statement

Answer 1

if (condition) statement1

[else statement2]

example:

if (i==j);

else if (j==k) printf ("i!=j, j==k\n);

else printf ("i!=j, j!=k\n);

here statement1 is an empty-statement, statement2 is another if-statement

There are three forms of statements

IF-THEN

IF-THEN-ELSE

IF-THEN-ELSIF

Sequence of statements is executed only if the condition evaluates to TRUE

If condition evaluates to FALSE or NULL, it does nothing

In either case control passes to next statement after the IF-THEN structure

IF THEN

statements;

END IF;

Sequence of statements in the ELSE clause is executed only if the condition evaluates to FALSE or NULL

IF THEN

statements;

ELSE

statements;

END IF;

Answer 2

It depends on the language however most use the following syntax:

if (expression) then statement else statement endif

Note that the "then" and "endif" keywords are not used in all languages since they are implied by the statement's structure and are normally only found in verbose languages such as BASIC. In C and C++, for instance, we have the following form:

if (expression) {

statement;

} else {

statement;

}

The expression must be a boolean expression; one that evaluates true or false. If the expression evaluates to a number, the expression evaluates true when the number is non-zero, otherwise it is false. When the expression is true, the first statement is executed otherwise the second statement is executed.

Often we do not wish to execute anything when an expression is false, only when it is true, so the else clause is optional.

if (expression) statement;

In languages that use braces {} to denote structure, they are usually optional for simple statements but mandatory for compound statements. A compound statement is a group of statements that are treated as being one statement.

Either statement may itself be an if statement (a nested if):

if (expression) {

if (expression) {

statement;

} else {

statement;

}

} else {

statement;

}

Spreading if statements over multiple lines and using whitespace indentation helps to highlight the logic and structure of the statement. It is not possible to show whitespace indentation here, but here's the same example using periods instead of whitespace:

if (expression) {

...if (expression) {

......statement;

...} else {

......statement;

...}

} else {

...statement;

}

Note the use of blank lines to separate the inner (nested) if from the outer if.

Answer 3

They are selection statements. If the condition with if is true then the statement attached with if part is executed, otherwise else part is executed.

Answer 4

"If" first tests a condition. If true, the program executes. If false, each "then else" is tested in order of existence (if there are "else" conditions).

Answer 5

A decision statement.

Answer 6

Binary logic.

Answer 7

hypothesis