Information Systems for you

Things To Do (page 61)
1(a)		Data is keyed in twice by two different people. The computer checks that the data is the same and only then is it accepted for processing. Or, the data is keyed in and then proofread against the original document and any errors are corrected.
(b)		Check that the first two digits are in the range 01 to 31. Next three characters must be alphabetic. Then four numbers must follow. The value of the first two digits may be checked against the month (e.g. in Sept can only go up to 30).

2(a)		check digit = 7 so incorrect.
(b)		check digit = 7 so correct.
(c)		check digit = 9 so correct.

3		The only ones to be detected are: Date of birth with a range check Exam fee paid with a range check

Examination Questions (page 334)
1(a)		It is a pre-input check performed by the program to make sure that the data being entered is reasonable/allowable.
(b)	(i) (ii)	To make sure that data is always entered for a certain field. For example each employee must have an employee number so a presence check checks that this is always filled in. To check that an item of data entered in a field is within an acceptable range. An example would be examination marks which could check if the mark was <=100 and >=0. If the mark lied outside this range then the data would not be accepted.

2(a)	(i) (ii) (iii) (iv)	Circle should be drawn around 200. No one could be employed that long. Range check should be ticked. Number of years >=0 and <=70

3(a)		Would only allow numbers to be entered into numeric fields but allow numbers and characters to be entered into text/character fields.
(b)		A range check that a number being entered into a numeric field is not too high or too low. Could use a range check to make sure that the quantity is not ordered is not 0 or less and is not greater than a certain value.
(c)		Check digits are numbers added to the end of a large group of numbers to ensure that the numbers before it are entered correctly. The computer removes this number and then uses all the other numbers to calculate it. If the numbers have been entered correctly, then the computer will calculate a number the same as the check digit. In this example the stock number could have a check digit at the end.

4(a)		Each word is checked against the dictionary for the spelling. Any words spelt correctly are left and the spellchecker only prompts the user if the word is not found in the dictionary. Alternative spellings are usually given.
(b)		Names of streets, people, slang words etc. Some words have alternative spellings e.g. computerize/computerise. These can be added to a custom dictionary for future reference.

5(a)		By using a paper document such as a questionnaire or survey. Could also use data capture forms. By interviewing people.
(b)		A pre-input check on data, performed by the software to make sure that the data entered is allowable/reasonable.
(c)		59 (i.e. the total of the student numbers)

6		Any two from: Inputting the data twice and only if the keystrokes are the same, will it be accepted. Carefully proofreading after entry. Going over the details after entry with the customer to confirm its correct entry.

7(a)		Any two from: A check digit could be included to check that the other numbers have been entered correctly. A lookup table could be used to check that the code exists as a stock item. A field check can be used to ensure that only numbers are included in the code.
(b)		Random access is needed.