- 2.2.6.1. -
Table of Contents
2. TMT Pascal Language Description
2.2. Pascal Language Structure
2.2.6. Types
2.2.6.1. Boolean Types
2.2.6.1. Boolean Types
The TMT Pascal compiler has four predefined Boolean types which are
Boolean (preferred), ByteBool, WordBool, and
LongBool.
The Boolean and ByteBool variables occupy one byte of memory,
a WordBool variable occupies two bytes, and a LongBool variable
occupies four bytes. Each Boolean type is an ordinal and can hold one of two
values: True or False. Expressions that evaluate to a logical "yes"
or "no" are of Boolean type. if, while, repeat
and other control statements work with Boolean expressions. The following code
fragment,
while not KeyPressed do ;
causes program execution to pause until a key is pressed on the keyboard.
KeyPressed is a procedure declared in the
CRT unit. The expression not KeyPressed
results in a Boolean value that determines whether the while loop is
executed.
not performs a logical NOT on the Boolean returned by
KeyPressed.
The constants True and False are
declared in the System unit as Boolean.
The evaluation model is controlled through the
$B compiler directive.
The default state is {$B-}, so the compiler generates
short-circuit evaluation code. In the {$B+} state,
the compiler generates a complete evaluation.
- 2.2.6.1. -
