Because the math works.

FALSE OR TRUE is TRUE, because 0 | 1 is 1.

... insert many other examples here.

Traditionally, C programs have conditions like

if (someFunctionReturningANumber())

rather than

if (someFunctionReturningANumber() != 0)

because the concept of zero being equivalent to false is well-understood.

Because the math works.

FALSE OR TRUE is TRUE, because 0 | 1 is 1.

... insert many other examples here.

Traditionally, C programs have conditions like

if (someFunctionReturningANumber())

rather than

if (someFunctionReturningANumber() != 0)

because the concept of zero being equivalent to false is well-understood.

Because the math works.

FALSE AND TRUE is TRUE, because 0 & 1 is 1.

... insert many other examples here.

Traditionally, C programs have conditions like

if (someFunctionReturningANumber())

rather than

if (someFunctionReturningANumber() != 0)

because the concept of zero being equivalent to false is well-understood.

Because the math works.

FALSE OR TRUE is TRUE, because 0 | 1 is 1.

... insert many other examples here.

Traditionally, C programs have conditions like

if (someFunctionReturningANumber())

rather than

if (someFunctionReturningANumber() != 0)

because the concept of zero being equivalent to false is well-understood.