Basicly there is no boolean value. The number 0 is considered to be false and all other numbers are considered to be true.... 1 is considered to be true because it is non-zero.
Boolean values and operations Constant true is 1 and constant false is 0. It is considered good practice, though, to write true and false in your program for boolean values rather than 1 and 0. The following table shows comparisons and boolean operations.
Zero is used to represent false, and One is used to represent true. For interpretation, Zero is interpreted as false and anything non-zero is interpreted as True.
undefined is true because undefined implicitly converts to false , and then ! negates it. Collectively, those values (and false ) are called falsy values. (Anything else¹ is called a truthy value.)
Zero is used to represent false, and One is used to represent true. For interpretation, Zero is interpreted as false and anything non-zero is interpreted as true. To make life easier, C Programmers typically define the terms "true" and "false" to have values 1 and 0 respectively.
The Boolean value of undefined is false.
You really don't have to look at the sun for very long at all for photochemical toxicity to occur, says Schuman. Retinal damage could occur in just 30–60 seconds, and sometimes even less, he says.
24 hoursAs a general rule of thumb, you should wait at least 24 hours before grouting. The adhesive should be dry and there should be no slippage or movement in your tile pattern.