Q(uick)BASIC Function: ABS

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ABS

A math function that returns the absolute value of a numeric expression

Worth knowing

Useful and cross-version information about the programming environments of QBasic and QuickBasic.

Syntax

ABS(numeric-expression)
SGN(numeric-expression)

Description/Parameter(s)

numeric-expression

Any numeric expression.

Example

PRINT ABS(45.5 - 100!) 'Output is: 54.5
PRINT SGN(12), SGN(-31), SGN(0) 'Output is: 1 -1 0

Syntax

ABS(numeric-expression)

Description/Parameter(s)

The absolute value is the unsigned magnitude of the argument. For example, ABS(-1) and ABS(1) are both 1.

Example

The following example finds an approximate value for a cube root. It uses ABS to find the difference between two guesses to see if the current guess is accurate enough.

DEFDBL A-Z
Precision = .0000001#
CLS                               'Clear the screen
INPUT "Enter a value: ", Value    'Prompt for input
'  Make the first two guesses.
X1 = 0.0# : X2 = Value
'  Go until the difference between two guesses is
'  less than the required precision.
DO UNTIL ABS(X1 - X2) < Precision
    X = (X1 + X2) / 2.0#
    ' Adjust the guesses.
    IF X * X * X - Value < 0.0# THEN
        X1 = X
    ELSE
        X2 = X
    END IF
LOOP
PRINT "The cube root is "; X

Sample Output:

Enter a value: 27 The cube root is 2.999999972060323

Syntax

ABS(numeric-expression#)

Description/Parameter(s)

The absolute value is the unsigned magnitude of the argument. For example, ABS(-1) and ABS(1) are both 1.

Example

This example finds the cube root of an input value. It uses the ABS function to test if the current guess is accurate. The DEFDBL statement is used to establish the default for the variables.

DEFDBL A-Z
Precision = .0000001#
CLS                               'Clear the screen.
INPUT "Enter a value: ", Value    'Prompt for input.
'Make the first two guesses.
X1 = 0#: X2 = Value
'Loop until the difference between guesses is
'less than the required precision.
DO UNTIL ABS(X1 - X2) < Precision
    X = (X1 + X2) / 2#
    ' Adjust the guesses.
    IF X * X * X - Value < 0# THEN
        X1 = X
    ELSE
        X2 = X
    END IF
LOOP
PRINT "The cube root is "; X

Sample Output:

Enter a value: 27 The cube root is 2.99999997206032