Operator Logika

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What are the Logical Operators

The logical operators are expressions which return a false or true result over a conditional expression. They are also used in assignments (an example of this would be shown later). Such  operators consist of simple logical operators, such as ‘Not‘ or ‘And‘. They should be used between two conditional expressions ; for example:

If (x = 0) AND (a = 2) then…

The Logical Operators

There are three types of logical operators, each of which are concerned with conditional expressions. These are:

AND
OR
NOT

All of these logical operators have a different effect on the conditional expressions. Let’s see what each of the logical operator does two (or more) conditional expressions…

And

If  *1(Str1 = ‘a’)  AND  *2(Str2 = ‘b’) then writeln(‘Yes, you got it right.’);

Expression 1

Expression 2 AND (result)
true true true
false true false
true false false
false false false

If expression 1 and expression 2 are both true(i.e. the user inputs ‘a’ and ‘b’ into variables ‘Str1’ and ‘Str2’ respectively), the message will be displayed. Above  is a table showing the possible combinations.

So, from the above table, one can conclude that for a logical operation such as AND, to give out a true result, both conditional expressions should be true.

OR

If  *1(Str1 = ‘a’)  OR *2(Str2 = ‘b’) then writeln(‘Yes, you got it right.’);

Expression 1

Expression 2 OR (result)
true
true true
false
true true
true
false true
false
false false

Either expression 1 or expression 2 should be true to display the message. If for example expression 1 is true and any other conditional expressions are false, the result is true! Above is a table(the truth table) showing the possible combinations.

So, from the above table, one can conclude that for a logical operation such as OR, to give out a true result, only one of the conditional expressions should be true.

NOT

Not is almost different from the two logical gates. It only accepts one input and is well-known as the ‘inverter’. If for example the result of two conditional expressions is true, the ‘not‘ operator would invert the result to false! So, the of the logical operator, ‘not‘, is to output the inverse of the input. The simple truth table for the not operator is:

Input
Output
true
false
false
true

Example of the AND Operator

Program Lesson6_Program1;
Uses Crt;
Var n1, n2 : string;

Begin
Writeln(‘Enter two numbers: (”0” & ”0” to exit)’);
Repeat
Write(‘No.1: ‘);
Readln(n1);
Write(‘No.2: ‘);
Readln(n2);
If (n1 = ‘0’) AND (n2 = ‘0’) then Halt(0);
Until (n1 = ‘0’) AND (n2 = ‘0’);
End.

Example of the OR Operator

Program Lesson6_Program2;
Uses Crt;
Var n1, n2 : String;

Begin
Writeln(‘Enter two numbers: (”1” & ”2” to exit)’);
Repeat
Write(‘No.1: ‘);
Readln(n1);
Write(‘No.2: ‘);
Readln(n2);
If (n1 = ‘1’) OR (n2 = ‘2’) then Halt;
Until (n1 = ‘1’) OR (n2 = ‘2’);
End.


Example of the NOT Operator

Program Lesson6_Program3;
Uses Crt;
Var n1 : String;

Begin
 Writeln('Enter two numbers: (any number except 0 to exit)');
 Repeat
  Write('No.1: ');
  Readln(n1);
  If not(n1 = '0') then Halt;
 Until not(n1 = '0');
End. 

The Boolean Expressions

The boolean expressions are the terms ‘true‘ and ‘false‘. These are simply similar to 1’s (for true) and 0’s(for false). They describe an expression whether it is false or true. The variable types over boolean expressions is the ‘boolean‘ type. Example:

Var bool : Boolean;

Example Program:

Program Lesson6_Program4;
Var quit : Boolean;
    a    : String;

Begin
 Repeat
  Write('Type ''exit'' to quit:');
  Readln(a);
  If a = 'exit' then quit := True else quit := False;
  If quit = True then Halt;
 Until quit = True;
End. 

Sumber:
http://pascalprogramming.byethost15.com/lesson6.php

One thought on “Operator Logika

    crusader 12 said:
    6 November 2012 at 2:47 pm

    Jelaskan dengan indonesia arti dari setiap operator logika???

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