Computer Science Notes

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* January 13, 2015

3.5 Book notes

compiled language: converted to machine language before running the program by using a translator called a compiler

compiler: piece of software that checks the syntactical and semantic structure of the program

examples C C++

programs run several times, but only has to compile once

interpreted language: NOT converted to machine language form but instead uses the interpreter to analyze the program

every time the program is executed repeatedly it is reinterpreted each time

even though the program isn’t converted into machine language form, the interpreter needs to be expressed in machine language form to run on the specific processor

instead of translating from one language to another, the compiled converts the program from high level language to machine language for the processor to run

however if the program is on a different processor then you would need to compile again

advantage to the compiled approach is speed b/c the translation to machine language is done once before the program or order is placed

advantage to the interpreted approach is flexibility because you can order with different languages, but this is lower because if you order the same thing the translation must take place all over again

3.5.1

the Java compiler produces a code called bytecode for a hypothetical computer called Java Virtual Machine

the JVM has an instruction set and manipulates various memory areas at run time

the compiler places the bytecode to be interpreted by the JVM into a class file THEN the JVM interprets the bytecode in the class file to execute the program

there are separate class files

for JVM to run, it must be able to locate the class file with the bytecode

JVM uses an envio variable named CLASSPATH to help it search and locate the class file for the program to run

Class notes 1/14/2015

Types: values, safety net idea, wants to know what you are dealing with, operations that you can apply to a program, specific...