| Data
Types |
|
The basic data types which can be used in a
high-level programming language are as follows:
| Data
Type |
Description |
Examples |
| Boolean |
True
or false (or any data that only has two possible values) |
TRUE
or FALSE
YES or NO |
| Character |
Any character you see on the keyboard and some more besides... |
'A',
'z', '8','?' |
| String |
A
number of characters... |
"Hello
World"
"Gerty Snoot" |
| Integer |
Whole
numbers, positive and negative |
23,
-45, 0 |
| Real |
All
numbers including fractions |
15.7,
-19.25, 8 |
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Storage
Data of different types uses different amounts of storage space in
memory or on disk.
| Data Type |
Storage Requirement |
| Boolean |
One BIT
- a single binary digit 0 or 1
|
| Character |
Usually one BYTE
Unicode characters (that
allow characters from all the world's languages) use 2 bytes of
storage.
|
| String |
A string is a
combination of characters. Storage requirement depends on the
length of the string.
In most languages maximum string lengths are set.
|
| Integer |
Storage requirements
for integers depend on the range
- the difference between the smallest and largest possible
integers.
Generally integers stored in n BITs
have a range of 2n values.
Example : Integers using
2 bytes (16 bits) have a range of 216 = 65536
values.
In other words possible values are 0 to 65535...
...or -32768 to +32767
|
| Real |
The data storage
requirements of real numbers depends on the method used to store
them. They will generally need more bytes of storage than
integers.
|
NB : It
is good programming practice to choose data types that use less storage
space if possible. For example, do not use real numbers if integers will
do.
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Operations on these data
types
| Data
Type |
Basic
Operations |
| Integer, Real |
All
arithmetic functions +, -, *, / etc.. Relational operations
- < less than
- > greater than
- <> not equal to
- >= greater than or equal to
- <= less than or equal to
(all these in the normal arithmetic
sense)
Truncating - Limits the number of
decimal places in a real number by chopping off unwanted digits
Rounding - Limits the number of
significant digits in a number by taking the 'nearest' value with the
required number of significant digits..
Example : 3.1415927
Truncated to 4 decimal places : 3.1415
Rounded to 4 decimal places : 3.1416
|
| Character, Strings |
Use
+ for string concatenation - adding strings together.
eg 'Bull' + 'frog' = 'Bullfrog'
Use < , > etc in the
alphabetical sense. These are all true...
- 'Abacus' < 'Beetle'
- 'Gannet' > 'Fish'
- 'Barracuda' > 'Barnacle'
|
| Boolean |
Usually
used in conditional statements...'Flag' may be a Boolean variable.... if
Flag = true then do...
or the equivalent statement...
if Flag then do ...
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