What is Opcode – Troubleinthepeace


I am quite new to this. I have tried to understand the difference between the mentioned terms clearly, however, I am still confused. Here’s what I found:

In assembler (or assembly) assembler language, mnemonic is an abbreviation for an operation. It is entered in the operation code field of each assembler program instruction. for example AND AC,37 means AND registers AC with 37. so AND, SUB and MUL are mnemonic. They are translated by the assembler.

You are viewing: What is Opcode

Instructions (statements) in assembly language are generally very simple, unlike instructions in high-level programming languages. In general, mnemonic is a symbolic name for a single executable machine language instruction (opcode), and there is at least one mnemonic opcode defined for each machine language instruction. Each instruction typically consists of an operation or opcode, plus zero or more operands.

assembly
thirty first
Jul 14, 2013Ahmed Taher
OPCODE : It’s a number interpreted by your machine (virtual or silicon) that represents the operation to perform

BYTECODE : Like machine code, except, mostly used by software-based interpreters (like Java or CLR)

MNEMONIC : The English word MNEMONIC means “A device such as a pattern, idea, or association that helps remember something.”. So it’s often used by assembly language programmers to remember the “ACTIVES” that the machine can do, like “ADD” and “MUL” and “MOV”, etc. This is compiler specific. .

MACHINE CODE: This is a sequence of numbers that turns the switches on and off in a computer to do a certain job – such as adding numbers, branching, multiplying, etc… This is completely machine specific and well documented by those processor implementer.

Festival: There are two “assemblies” – an assembly program is a sequence of spells and operands passed to a “compiler” that “assembles” the symbols and operands into executable machine code. Optionally a “linker” links assemblies and creates an executable.

The second “assembly” in “CLR”-based languages ​​(.NET languages) is a string of CLR code that is passed metadata information, a kind of library of executable code, but not directly executable.

41
Aniket did a great job, but I’ll go too.

First, understand that at the lowest level, computer programs and all data are just numbers (sometimes called words), in some kind of memory. Most commonly these words are multiples of 8 bits (1 and 0) (such as 32 and 64) but not necessarily, and in some processors, each word is significantly larger. Those are just numbers represented as a string of 1s and 0s, though, or above and beyond if you like. What the numbers mean depends on what/who has ever read them, and in the case of the processor, it reads memory one word at a time and based on the number (instructions) it sees, executes it. some action. Such actions may include reading a value from memory, writing the value to memory, modifying the value it has read, jumping to another place in memory to read instructions from there.

In the early days, a programmer would literally flip switches on and off to change memory, turn lights on or off to read 1s and 0s, since there were no keyboards, screens, etc. As time went on Over the years, memory grew larger, processors became more complex, display devices and keyboards for input were conceived, and with that, easier ways to program.

Anaphet explains:

The OPCODE is the part of the instruction word that is interpreted by the processor as representing the operation to be performed, such as read, write, jump, add. Many instructions will also have OPERANDS that affect the execution of the instruction, such as telling where in memory to read or write, or where to jump. So if the instructions are 32 bits in size for example, the processor can use 8 bits for the opcode and 12 bits for each of the two operands.

A step up from toggle switches, code can be entered into the machine using a program called “monitor”. The programmer will use simple commands to say which memory they want to modify and enter the CODE, e.g. in base 16 (hex) use 0 to 9 and A to F for the digits.

Although better than toggling a switch, entering machine codes is still slow and error-prone. A step up from that is the assembly CODE, which uses the easier to remember MNEMONICS in place of the actual number representing an instruction. ASSEMBLER’s job is mainly to convert the mnemonic form of the program into the corresponding machine code. This makes programming easier, especially for jump instructions, where part of the instruction is a memory address to jump to or some words to skip. Programming in machine code requires the computations necessary to construct the instructions correctly, and if some code is added or removed, the jump instructions may need to be recalculated. The compiler handles this for the programmer.

This leaves BYTECODE, which is essentially the same as machine code, in that it describes low-level operations like reading and writing memory and basic computations. Bytecode is usually conceived to be generated when CREating a higher level language, for example PHP or Java, and unlike machine code for many hardware based processors, can have operations to support features higher level specifics One key difference is that the processor of the bytecode is usually a program, although the processor was created to interpret some of the bytecode specifications, e.g. the processor called SOAR (Smalltalk On A RISC) for Smalltalk bytecode. Encoder machine code, for some types of processors such as CISC and EISC (e.g. Linn Rekursiv, from the people who created the record player), the processor itself contains a program that interprets the machine instructions , hence the similarity.

See also: What is Ligament?

The following line is the delimited x86 code.

68 73 9D 00 01 Push 0x01009D73 68 to be opcode. For the following bytes, it represents To push tutorial of x86 festival = language. The push instruction pushes data of 4 bytes (32 bits) in length for stacking. Word Push is just one mnemonic represents opcode 68. Each byte 68 ,- seventy three , 9D , 00 , 01 to be machine code.

machine code for real machine (CPU) but bytecode is the pseudocode for the virtual machine.

When you write a Java code. Java compiles your code and generates bytecode. (A .Class file) and you can execute the same code at any platform without change.

Java Code | | BYTE CODE ________________|___________ | | | x86 JVM SPARC JVM ARM JVM | | | | | | x86 SPARC ARM MACHINE CODE MACHINE CODE MACHINE CODE
“Assembly” derives from very early “compiler” code that would “assemble” programs from multiple files (what we will now call “include” files). . compiler “does not support include files and therefore does not ‘assemble’.

It is interesting to note that “compilers” were invented to support “subroutines”. Initially there are “inside” and “external” subroutines. The “internal” subroutines are what we will call “inline”, while the “external” subroutines are accessed through the primitive “calling” mechanism. There was much controversy at the time as to whether “external” subroutines were a good idea.

“Mnemonic” comes from the name of the Greek god Mnemosyne, the goddess of memory. Anything that helps you memorize stuff is a “memory device”.

I recently read a good article on this, Difference between Opcode and Bytecode, hence wanted to share with anyone after a good explanation on the subject. All credits go to the original author .

*

Opcode :

Opcode stands for active code. As the name implies, an opcode is a type of code that tells the machine what to do, i.e. what operation to do. Opcode is a type of machine language instruction.

Bytecode :

Bytecode is similar in essence to opcode, as it also tells the machine what to do. However, bytecode is not designed for processor execution livewhich is another program.<.__.> It is most commonly used by a software-based interpreter such as Java or <~ # ~> clr <~ # ~> . They convert each generality guide the machine to a Specifically instructions or machine instructions for the computer’s processor to understand.

See more:

<.__.> In fact, the name bytecode comes from scripts have one-byte opcodes followed by optional parameters .

C++ code to test the Collatz conjecture is faster than handwritten assembly – why?

Replacing 32 bit loop counter with 64 bit introduces crazy performance bias

Why doesn’t GCC optimize a * a * a * a * a * a to (a * a * a) * (a * a * a)?

To be

What is the purpose of the LEA guidelines?

Is it possible to “decompile” Windows .exe? Or at least watch the assembly?

How to achieve a theoretical maximum of 4 FLOPs per cycle?

How do you get compiler output from C/C++ source in gcc?

Why aren’t programs written in assemblies more often?

How to run a program without operating system?

When is assembly faster than C?

Test score %eax%eax

Why does GCC use multiplication by a strange number in performing integer division?

What is the function of the push/pop instructions used on the registers in the x86 assembly?

What is the purpose of the RBP register in the x86_64 compiler?

Can num++ be atomic for “int num” ?

What is the purpose of ESI & EDI registration?

Is “switch” faster than “if”?

Execution protection from reverse engineering?

How can one see the contents of the stack with gdb

Source: internet

About Troubleinthepeace

Troubleinthepeace specializing in synthesizing information about daily life activities

View all posts by Troubleinthepeace →

Trả lời

Email của bạn sẽ không được hiển thị công khai.