All data is stored in memory in binary form, but this raises a problem:

The binary form of the integer 36 is the same as the binary form of the character '$' (see 3.05 - ASCII and Unicode).

How does the computer decide which of these interpretations is correct?

The data type of a variable determines how its binary form in memory is interpreted.

Table 1 shows the five main data types.

Table 1

Name	Pseudo-code	Python	Description	Examples
Integer	INT	int	A whole number.	5, -123, 0
Float (or real)	REAL	float	A number with a decimal part.	1.23, -10.0, 0.15
Boolean	BOOL	bool	Either "true" or "false".	True, False
Character	CHAR	N/A	A single character.	'a', '5', '?'
String	STRING	str	A collection of characters.	"abcd", "!@#", ""

You can convert between different data types, as shown in Example 1 (pseudo-code) and Example 2 (Python).

Example 1
INT_TO_STRING(123)     "123"
STRING_TO_INT("123")   123
REAL_TO_STRING(1.23)   "1.23"
STRING_TO_REAL("1.23") 1.23


Example 2
str(123)      # "123"
int("123")    # 123
str(1.23)     # "1.23"
float("1.23") # 1.23


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Which data type do we use as the condition of an IF statement?

A boolean: it needs to evaluate to either True or False.

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