Boolean expressions

Boolean are represented using algebra.

Consider these :

5 < 10
x < 10
x < y

Each of these statements is a Boolean expression in the form of algebra. The only difference between them is that the first expression uses numbers and the second and third use . If we give x the value 5 and y the value 10, then each statement is identical.

Each statement is also a comparison. The statements compare the first value with the second. In this case we are saying that 5 is less than 10.

Boolean values

In , each statement is a comparison, and each comparison gives a Boolean value – True or False.

When x = 5 and y = 10 then:

Statement	Expression	Boolean value
y > x	y is greater than x	True. When x is 5 and y is 10, then y is greater than x.
x < y	x is less than y	True. When x is 5 and y is 10, then x is less than y.
x = y	x equals y	False. When x is 5 and y is 10, then x does not equal y.
x<>y	x does not equal y	True. When x is 5 and y is 10, then x does not equal y.

Statement	y > x
Expression	y is greater than x
Boolean value	True. When x is 5 and y is 10, then y is greater than x.

Statement	x < y
Expression	x is less than y
Boolean value	True. When x is 5 and y is 10, then x is less than y.

Statement	x = y
Expression	x equals y
Boolean value	False. When x is 5 and y is 10, then x does not equal y.

Statement	x<>y
Expression	x does not equal y
Boolean value	True. When x is 5 and y is 10, then x does not equal y.

When x = 5 and y = 5, we get a different set of Boolean values:

Statement	Expression	Boolean value
y > x	y is greater than x	False. When x is 5 and y is 5, then y is not greater than x.
x < y	x is less than y	False. When x is 5 and y is 5, then x is not less than y.
x = y	x equals y	True. When x is 5 and y is 5, then x is equal to y.
x<>y	x does not equal y	False. When x is 5 and y is 5, then x is equal to y.

Statement	y > x
Expression	y is greater than x
Boolean value	False. When x is 5 and y is 5, then y is not greater than x.

Statement	x < y
Expression	x is less than y
Boolean value	False. When x is 5 and y is 5, then x is not less than y.

Statement	x = y
Expression	x equals y
Boolean value	True. When x is 5 and y is 5, then x is equal to y.

Statement	x<>y
Expression	x does not equal y
Boolean value	False. When x is 5 and y is 5, then x is equal to y.

Each Boolean expression gives a result that we can use in selection and iteration.

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Boolean logicBoolean expressions