Java Reference
In-Depth Information
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1
1
.
A computer is an electronic device capable of performing arithmetic and
logical operations.
2
.
A computer system has two kinds of components: hardware and software.
3
.
The central processing unit (CPU) and the main memory are examples of
hardware components.
4
.
All programs must be brought into main memory before they can be
executed.
5
.
When the power to the computer is switched off, everything in main
memory is lost.
6
.
Secondary storage provides permanent storage for information. Hard disks,
floppy disks, flash-memory, ZIP disks, CD-ROMs, and tapes are examples
of secondary storage.
7
.
Input to the computer is done via an input device. Two common input
devices are the keyboard and the mouse.
8
.
The computer sends output to an output device, such as the computer
monitor.
9
.
Software refers to programs run by the computer.
10
.
The operating system monitors the overall activity of the computer and
provides services.
11
.
Application programs perform a specific task.
12
.
The most basic language of a computer is a sequence of
0
s and
1
s called
machine language. Every computer directly understands its own machine
language.
13
.
A bit is a binary digit,
0
or
1
.
14
.
A sequence of
0
s and
1
s is called a binary code or a binary number.
15
.
A byte is a sequence of eight bits.
16
.
One kilobyte (KB) is 2
10
¼
1024 bytes; one megabyte (MB) is 2
20
¼
1,048,576 bytes; one gigabyte (GB) is 2
30
¼
1,073,741,824 bytes; one
terabyte (TB) is 2
40
¼
1,099,511,627,776 bytes; one petabyte (PB) is
2
50
is 2
60
¼
1,125,899,906,842,624 bytes; one exabyte (EB)
¼
is 2
70
¼
1,152,921,504,606,846,976 bytes; and one zettabyte (ZB)
1,180,591,620,717,411,303,424 bytes.
17
.
Assembly language uses easy-to-remember instructions called mnemonics.
18
.
Assemblers are programs that translate a program written in assembly
language into machine language.
19
.
To run a Java program on a computer, the program must first be translated
into an intermediate language called bytecode and then interpreted into a
particular machine language.
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