# 18th Example - Count Area of A Circle on PL/SQL

The
circle is of mathematical shape that can be found in the real world such as car
wheels, the pipe, cable cross-section. Circle has an area and perimeter
that can be calculated with mathematical
formulas. The formula to calculate the
area of a circle is pr

^{2}, where p is a constant with a value of 3,14 and r is the radius of the circle. The following PL / SQL block to calculate area of a circle:**DECLARE**

**phi CONSTANT NUMBER := 3.14;**

**r NUMBER;**

**hasil NUMBER;**

**BEGIN**

**r := &input_r;**

**hasil := phi * r * r;**

**DBMS_OUTPUT.PUT_LINE ('Luas Lingkaran = '||hasil);**

**END;**

**/**

In
the declaration
of PL/SQL block above there are 3 variables. One variable is the constant phi. Constant is a variable whose value will not change when the program executed. Contents of PL/SQL block that will calculate the area of a circle pr

^{2}value stored in the variable hasil. Suppose we fill the value of the variable r 10, the output shown is "Area of Circle = 314".
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