ALPHA Function

The logical function ALPHA evaluates an expression to determine if it is a string containing only alphabetic characters.

Format

ALPHA(expr)

Parameter(s)

expr	String expression to be tested.

Description

The ALPHA function determines whether the expression is an alphabetic or nonalphabetic string. If the expression contains the characters A through Z or a through z (ASCII 65 - 90, 97 - 122), it evaluates to true and a value of 1 is returned. If the expression contains any other character (such as numeric or special characters), it evaluates to false and a value of 0 is returned.

Examples

If the variable NAME contains "HENRY FRENKL", then:

ALPHA(NAME)

returns 1. However, if NAME contains "HENRY FRENKL4th", the ALPHA function returns 0.

In the next application, airline reservations require the traveler’s starting point and final destination. The travel agent must enter these with the 3-letter code assigned to airports.

PROMPT " "

PRINT @(-1)

PRINT @(2,2) : "ENTER FLIGHT DATE: ":

INPUT @(30,2) DATE "D"

PRINT @(2,4) : "ENTER FLIGHT NUMBER: ":

INPUT @(30,4) FLTNO,3 "0"

PRINT @(2,6) : "STARTING POINT: ":

LOOP

INPUT @(30,6) START,3

IF NOT ( ALPHA( START )) THEN

INPUTERR "PLEASE ENTER 3-LETTER

AIRPORT CODE."

END

UNTIL ALPHA(START) DO

REPEAT

PRINT @(2,8) : "FINAL DESTINATION: ":

LOOP

INPUT @(30,8) DEST,3

IF NOT( ALPHA( DEST )) THEN

INPUTERR "PLEASE ENTER 3-LETTER

AIRPORT CODE."

END

UNTIL ALPHA(DEST) DO

REPEAT