Input validation

Input validation is a standard algorithm used to make sure the user doesn't input unacceptable data.

The algorithm typically uses a conditional loop.

Example code – validating numbers from 1 to 10 show

VB code	Pseudocode
`Do userInput = InputBox("Please enter a number from 1 to 10") If userInput <1 Or userInput >10 Then MsgBox ("Please re-enter. Your number was not in the range 1 to 10.") End If Loop Until userInput >=1 And userInput <=10`	REPEAT SEND "Please enter a number from 1 to 10" TO DISPLAY RECEIVE userInput FROM KEYBOARD IF userInput <1 OR userInput >10 THEN SEND "Please re-enter. Your number was not in the range 1 to 10." TO DISPLAY END IF UNTIL userInput >=1 AND userInput <=10

Example code – validating to ensure whole numbers only show

VB code	Pseudocode
`Do userInput = InputBox("Please enter a whole number") If userInput <> Int(userInput) Then MsgBox ("Please re-enter. Your number was not an integer.") End If Loop Until userInput = Int(userInput)`	REPEAT SEND "Please enter a whole number" TO DISPLAY RECEIVE userInput FROM KEYBOARD IF userInput ≠ INT(userInput) THEN SEND "Please re-enter. Your number was not an integer." TO DISPLAY END IF UNTIL userInput = INT(userInput)

Example code – validating to ensure letters only show

VB code	Pseudocode
`Do userInput = InputBox("Please enter a letter") If Asc(userInput) <65 Or (Asc(userInput) >90 And Asc(userInput) <97) Or Asc(userInput) >122 Then MsgBox ("Please re-enter a letter") End If Loop Until (Asc(userInput) >=65 And (Asc(userInput) <=90) Or (Asc(userInput) >=97) And Asc(userInput) <=122)`	REPEAT SEND "Please enter a letter" TO DISPLAY RECEIVE userInput FROM KEYBOARD IF ASC(userInput) <65 OR (ASC(userInput) >90 AND ASC(userInput) <97) OR ASC(userInput) >122 THEN SEND "Please re-enter a letter" TO DISPLAY END IF UNTIL (ASC(userInput) >=65 AND (ASC(userInput) <=90) OR (ASC(userInput) >=97) AND ASC(userInput) <=122)

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mph@ghscomputing.co.uk

Updated 09 December 2018