computor science

Database Definition

A place where information is stored and organised so it can be easily found, updated, and managed.

Data

Raw facts and figures like "9" or "Sibani" that have no meaning on their own until they are processed.

Information

Data that has been processed and organised into a context that gives it meaning (e.g. "Sibani is in Year 9").

Table

The main structure of a database where data is stored in a grid of rows and columns.

Record

One full row in a database table representing one single item or person (e.g. all the data for Sibani).

Field

One column in a database table representing one specific category of data (e.g. FirstName or DateOfBirth).

Primary Key

A field that uniquely identifies each record in a table. It cannot be duplicated and cannot be left blank.

Foreign Key

A field in one table that links to the Primary Key in another table.

Relationship

A link between tables using keys in a relational database.

Query

A request used to search for, filter, or display data from a database.

Short Text Data Type

A data type used to store short pieces of text such as names or addresses.

AutoNumber Data Type

Automatically creates a unique number for every new record; usually used for Primary Keys.

Boolean (Yes/No) Data Type

Used for fields that only have two possible answers such as "Allergy?".

Validation Rule

A check made by the computer to ensure inputted data is sensible and within limits.

Presence Check

A validation rule that ensures a field is not left blank.

Length Check

A validation rule that ensures data is not too short or too long.

Range Check

A validation rule that ensures a number is within limits.

Type Check

A validation rule that ensures the correct type of data is entered.

Flat-File Database

A database with only one table of data.

Relational Database

A database with multiple tables linked together.

Paper-Based Disadvantage

Takes up a lot of space, is slow to search through, and can be easily lost or damaged.

Computer-Based Advantage

Easy to organise and look through data, allows fast searching, and improves security.

Paper-Based Advantage

Easy to use, cheap, and simple to set up.

Computer-Based Disadvantage

Expensive, needs electricity/computer, likely needs training and can have technical issues.

Nibble

A group of 4 bits.

Byte

A group of 8 bits.

Binary

A base 2 number system, containing only 0 and 1

Denary

A number system using base 10.

Hexadecimal

A number system using base 16 (0–9 and A–F).

Overflow

When a number is too large to fit in the available number of bits.

ASCII

American Standard Code for Information Interchange; a system that turns characters into numbers so computers can store text.

Variable

A named container that stores data which can change.

Data type

The type of data a value is (e.g. integer, string, float)

String

Text data (e.g. "hello")

Integer

Whole numbers (e.g. 5)

Float

Decimal numbers (e.g. 2.5)

Type conversion

Changing data from one type to another (e.g. string → integer)

==

Checks if two values are equal

!=

This is the not equal to operator. It checks if two values are not equal to each other.

>>

Checks if one value is greater than another

<

Checks if one value is less than another

>=

Checks if a value is greater than or equal to another

<=

Checks if a value is less than or equal to another

= vs ==

= assigns a value, == compares values

free point (delete later)

k

/

Normal division (gives exact answer)

//

Floor division, divides and round down to the nearest whole number

%

Divide the first number by the second number, round the result down to the nearest whole number, multiply that by the second number, then subtract that from the first number. The result is the remainder, which is what the modulus operator (%) gives.

FOR loop

Used when you know how many times to repeat

WHILE loop

Used when repetition depends on a condition

Infinite loop

A loop that never stops because the condition is always True

if statement

A selection statement that runs code only if a condition is true

not operator

Reverses a condition

or operator

Returns True if at least one condition is True

if / elif / else

Used for selection in Python.
if runs code when a condition is true.
elif tests another condition if the previous if was false.
else runs code if none of the conditions are true.