# QB64.com

## QB64 is a modern extended BASIC programming language that retains QBasic/QuickBASIC 4.5 compatibility and compiles native binaries for Windows, Linux, and macOS.

The SQR function returns the square root of a numerical value.

## Syntax

square_root = SQR(value)

## Description

• The square root returned is normally a SINGLE or DOUBLE numerical value.
• The value parameter can be any positive numerical type. Negative parameter values will not work!
• Other exponential root functions can use fractional exponents([^](^)) enclosed in parenthesis only. EX: root = c ^ (a / b)

## Example(s)

Finding the hypotenuse of a right triangle:

``````
A% = 3: B% = 4
PRINT "hypotenuse! ="; SQR((A% ^ 2) + (B% ^ 2))

``````
``````
hypotenuse = 5

``````

Finding the Cube root of a number.

``````
number = 8
cuberoot = number ^ (1/3)
PRINT cuberoot

``````
``````
2

``````

Negative roots return fractional values of one.

``````
number = 8
negroot = number ^ -2
PRINT negroot

``````
``````
.015625

``````

Explanation: A negative root means that the exponent value is actually inverted to a fraction of 1. So x ^ -2 actually means the result will be: 1 / (x ^ 2).

Fast Prime number checker limits the numbers checked to the square root (half way).

``````
DEFLNG P
DO
PRIME = -1   'set PRIME as True
INPUT "Enter any number to check up to 2 million (Enter quits): ", guess\$
PR = VAL(guess\$)
IF PR MOD 2 THEN              'check for even number
FOR P = 3 TO SQR(PR) STEP 2 'largest number that could be a multiple is the SQR
IF PR MOD P = 0 THEN PRIME = 0: EXIT FOR 'MOD = 0 when evenly divisible by another
NEXT
ELSE : PRIME = 0 'number to be checked is even so it cannot be a prime
END IF
IF PR = 2 THEN PRIME = -1 '2 is the ONLY even prime
IF PR = 1 THEN PRIME = 0  'MOD returns true but 1 is not a prime by definition
IF PRIME THEN PRINT "PRIME! How'd you find me? " ELSE PRINT "Not a prime, you lose!"
LOOP UNTIL PR = 0

``````
``````
Enter any number to check up to 2 million (Enter quits): 12379
PRIME! How'd you find me?

``````

Note: Prime numbers cannot be evenly divided by any other number except one.