highschool/Grade 9/Computer Science.md

Computer Science Review Sheet

Exam Layout

Part	Description	Marks
A	True / False	10
B	Multiple Choice - All java code learnt, selection, loops, methods, Arrays, methods, strings	38
C	Short & Long Answers - Compare and contrast short code, methods, problem solving	20
Total		68

Intro To Programming

Comments: are used to explain and clarify program ocde for human reader

Operator	Uses	Description
+	a + b	Addition
-	a- b	Subtraction
*	a * b	Multiplication
/	a / b	Division
%	a % b	Mod, the Remainder

BEDMAS rules still apply

Strings

String: means a group of many characters
String Concatenation: means that two strings are combined into one using the “r” sign

Varaibles

Holder for data
We can use words instead of just a single letter - can store more than just numbers
a place in memory (RAM: random access memory) where it can be stored or referred to
- Name, type, value

To declare a variable 1. Name 2. Data Type

A variable is the name of a reserved memory location
A varaible name is called an identifier
Reserved words cannot be used as an identifier

Java Primitives

Variables can be created for any of the data types listed
The chart shows examples of how to create a new variable for each primitive

Type	Range	Size	Variable	Declaration
byte	-128 to 127	8 bits	bits_8	byte bits_8;
short	-32768 to 32767	16 bits	TALL	short TALL;
int	-2 billion to 2 billion	32-bits	sum	int sum;
long	-9 quintillion to 9 quintillion(huge)	64 bits	mile	long mile;
float	-3.4e+/-38 to 3.4e+/-38	32 bits	pi	float pi;
double	-1.7e+/-308 to 1.7+/-308	64 bits	stuff	double stuff;
char	Single (unicode) characters	16 bits	letter	char letter;