IGCSE Computer Science Paper 2
Terms in this set (50)
a step-by-step procedure for solving a problem
A five-part system consisting of hardware, software, data, and people and communications
Entering data that should be acceptable to the solution.
abnormal test data
Test data that is clearly incorrect and should produce an error.
Test data on the boundary of what the program will accept
Data either side of the range extremes. For example in a range of 1 to 10 boundary data will include 0, 1, 10 and 11
Is the automated checking by a program that data is reasonable before it is accepted into a computer system.
checks that only numbers within a specified range (upper and lower limit) are accepted.
E.G. percentage marks between 0-100 ONLY
Length Check (2)
1. checks that data contains an exact number of characters. E.G. that a password must by exactly 8 char in length.
2. That the data entered is a reasonable number of character e.g. family name should be between 2-30 char
checks that the data entered is of a given data type. E.G. number of brothers or sisters would be an integer (whole number)
checks that when a string of characters is entered it doesn't contain any invalid characters or symbols. E.G. Doesn't contain % or !@£ in a phone number
checks that the character entered conform to a pre-defined pattern. E.G.the Cub number must be in the form CUB9999
Check to make sure that data has been entered into a field. E.G. email on online transaction
Is the final digit included in a code; calculation from all the other digits in the code. E.G. used for barcodes, product code, etc.
What can types of errors can check digits detect (4)
- Incorrect digit entered, e.g. 5453 instead of 5444
- Transposition error where 2 numbers have changed order, e.g. 5306 instead of 5360
- Extra digits, e.g. 53000 instead of 530
- phonetic errors, e.g. 13 instead of 30.
Checking that data has been accurately copied into the computer or transferred from one part of a computer system to another
Verification methods: (4)
- double entry
- screen check
- parity check
Data is entered twice, sometimes by different operators; the computer system compares both entries and outputs an error message requesting that the data is entered again if they are different.
is a manual check completed by the user who is entering the data. When the data entry is complete the data is displayed on the screen and the user is asked to confirm that it is correct before continuing.
The effectiveness of a solution
- 4 factors
1. Does the solution work for all sets of data?
2. Does the solution have any unnecessary processes that are never used?
3. Are any actions repeated more often than necessary?
4. Can the solution be simplified and still work as well?
Shows when values are assigned to a variable
A named data store that contains a value that does not change during execution of a program
A named data store that contains a value that may change during execution of a program
Positive/negative number with fractional part
A sequence of characters
A single value of either TRUE or FALSE
a list where each item can be identified by an index number
an item in a list
the number of each element within a one-dimensional array
A trace table can be used to record the results from each step in an algorithm; used to record value of an item each time it changes
set of test data is all the items of data required to work through a solution.
Top Down Design
breaking down of a computer system into a set of sub-systems and so on until each sub-system performs a single action
show top=down designs in diagrammatic form
A set of programming instructions for a given task that is already available for use
pre tested and performs a task frequently required
a set of programming instructions for a given task that forms a sub-system not the whole system
describes what an algorithm does by using english key words that are very similar to those used in a high-level programming language
describes what an algorithm does by using a standard set of symbols joined by lines showing the direction of flow
Statements are followed in sequence so the order of the statements in program is important
allows data to be picked out according to given criteria
Structured collection of data
contains data about one type of item, etc. using rows and columns
Row within a table contains data about single item, person or event, etc.
A column which contains one specific piece of information
unique reference for each record
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