How program written in high level language changed into machine code?

Answer 1

The way you stated your question is rather confusing, but what I think you're asking is, "are programs written in high level languages called compiled programs?"

Well, not all high level languages are compiled. Python, for example, is interpreted, instead of compiled. Many, such as C++ (although that is more medium level) are compiled. In general, one would not call a program written in a compiled language a "compiled program" until it's been compiled.

Answer 2

No.

All programs have to be converted to machine code to run.

An interpreter does the conversion at every run time and a compiler does the conversion ahead of time, producing an executable program that may be run many times.

Answer 3

High-level source code is converted to low-level machine code using software. These software programs are known as compilers or interpreters. An interpreter is a program that translates a high-level source into machine code at runtime. That is, the code must be translated each and every time it is executed by the interpreter. Interpreted software does not perform very well compared to native machine code equivalents, however the exact same source can be executed upon any machine with a suitable interpreter. Machine code programs can only be executed upon the machine architecture for which they were intended.

A compiler is a program that takes a high-level input and produces a lower-level output. The lower-level output may be machine code itself, however compilers can also be used to create an assembly language source, a byte code source, or even another high-level language source (albeit one with fewer abstractions than the original source). It is not (yet) possible to convert a low-level source to a high-level source; machines simply aren't yet capable of the "thought processes" required to produce ad-hoc abstractions in the same way a human can.

High-level languages are generally classified as being interpreted or compiled languages depending on how they are converted, however there's really no practical reason why an interpreted language cannot be compiled or why a compiled language cannot be interpreted; we simply need to write the appropriate software to perform the conversion we require.

Java is conventionally regarded as being a compiled language, however in reality it is both compiled and interpreted. The reason is that the source code is compiled against a virtual machine rather than a physical one. The "virtual machine code" produced by the Java compiler is known as Java byte code. This byte code is suitable for interpretation by any Java virtual machine (JVM). This has several advantages over traditional interpreted languages in that byte code can be interpreted with much greater efficiency than the original source code could; most of the hard work is carried out by the compiler.

C and C++ are conventionally regarded as being compiled languages, both being capable of producing native machine code and/or an assembly language source. However, C++ didn't start out that way; having evolved from C, the original C++ compiler produced a C language source which then had to be compiled by the C compiler.

Answer 4

It depends on whether the source is compiled, interpreted or both.

An interpreted program is one that is converted to machine code by a runtime program known as the interpreter. Typically, the program's source code is parsed by the interpreter and translated into the required machine code, one statement at a time. Interpreted programs do not perform well because there is little or no optimisation of the code and the same statements need to be re-interpreted every time they encountered.

A compiled program is one where the entire program is converted to machine code. Compiled programs perform extremely well because the compiler can optimise the code to take full advantage of the underlying hardware features. C++ is a typical example of a compiled programming language. Compilation begins with a precompilation stage which processes the macro definitions and precompiler directives in each translation unit, pulling in headers and performing text replacements to produce intermediate source files. These intermediates are then compiled to produce object files. Finally, the object files are linked together with any required external libraries to produce the final executable. Although C++ source code is highly portable, the source code must be recompiled separately upon each target platform.

Java is both compiled and interpreted. The Java compiler produces byte code which is suitable for interpretation by the Java Virtual Machine (JVM). The byte code is the same regardless of which physical platform you perform the compilation on, thus compiled Java programs are highly-portable. The JVM performs the low-level interpretation of the byte code to machine code.

Answer 5

Compile into object code that is then linked into executable machine code.

Answer 6

A special program is invoked to do that. Such a program is called an assembler (for assembly language), or a compiler (for most languages).