18-08-2012, 05:09 PM
core java full report
02-corejava.pdf (Size: 1.62 MB / Downloads: 523)
General Purpose Computers
Most computers that we encounter are
application specific…
n Light switches, microwave oven controller,
VCR timer, DirecTV receiver
n GPCs are different…
n GPCs are built as generic problem solving
machines
n Programming is the bridge from the generic
tool to a useful “machine”
GPC (Computer) Organization
CPU – Central Processing Unit
Primary location for computations
I/O – Input and Output Subsystem
Devices and communication bus for user
interaction, import/export of data and
permanent storage
RAM – Random Access Memory
High speed, volatile, “scratchpad”
High Level Languages
Machine and Assembly Language are
very hard to use…
• Try computing a 3rd order integral in assembly…
• How about writing a GUI?
So we create high level languages and
compilers for translating high level
programs into assembly
Caveats of the JAVA Way
Performance
• Clearly, JAVA will always be slower than a
natively coded application
• JIT JVM technology brings most applications
within 30% of native code
• Latest HotSpot JVMs are within 5% of C++
Touching the hardware
• Not all local devices will have an interface
through the JVM… your favorite USB scanner
may simply not work (at least, for now…)