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Encyclopedia > Opcode

Microprocessors perform operations using binary bits (on/off/1or0). Eight bits is equal to a byte (on most modern processors), and two bytes is equal to a word.

As an example let's design a crude 4-bit microprocessor.

All registers, ALUs, counters, and addresses have a data path of 4-bits.

Also, all of our instructions must fit in a 3-bit address.

These are the

 op-codes mnemonic operations explanation 000 ADD add A to B and store in b 001 mov move A to B and store in b 010 Jmp jump value in A 011 xorA xor A with next op-code store in b 100 clrA clear A 101 return return to pointer 110 counter counter value 111 end end program 

when the op-code values are active at the decoders logic inputs the desired operations are performed..

This is a better explanation then whats below..cleanUpLater..

, each of which is assigned a numeric code called an opcode. To assist in the use of these numeric codes, mnemonics are used as textual abbreviations. It's much easier to remember ADD than 05, for example. A mnemonic (Pronounced in American English, in British English) is a memory aid. ...

Opcodes operate on registers, values in memory, values stored on the stack, I/O ports, the bus, etc. They are used to perform arithmetic operations and move and change values. Operands are the things that opcodes operate on. In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... Memory is a property of the human mind: the ability to retain information. ... A stack is a data structure that works on the principle of Last In First Out (LIFO). ... This article is about the computer interface. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers. ...

Byte codes are another term for opcodes, especially when they are used to describe higher level constructs as is the case with the Java Language's JVM (Java Virtual Machine). For instance, byte code 1A might be the "iconst_2" instruction which pushes the number 2 on the stack. This is a slightly higher level of abstraction than opcodes, which might need to load the number 2 into a register, and then push the register's value on the stack. Byte-code is a sort of intermediate code that is more abstract than machine code. ... Java is an object-oriented programming language developed initially by James Gosling and colleagues at Sun Microsystems. ... A Java virtual machine or JVM is a virtual machine that runs Java byte code. ...


  Results from FactBites:
OPCODE (360 words)
OPCODE is a new small collision detection library.
Hybrid trees (OPCODE 1.3) keep a maximum of 16 triangles per leaf and reorganize client triangle lists, to eventually need roughly 16 times less ram than OPCODE’s standard trees.
Speed hit is often negligible, and volume queries can actually run faster than OPCODE 1.2 due to less cache misses (reorganizing clients arrays also helps in this regard).
opcode (897 words)
These opcode blocks are very similar to instruments (and are, in fact, implemented as special instruments), but cannot be called as a normal instrument e.g.
A user-defined opcode block must precede the instrument (or other opcode) from which it is used.
Similarly to instruments, the variables and labels of a user-defined opcode block are local and cannot be accessed from the caller instrument (and the opcode cannot access variables of the caller, either).
  More results at FactBites »



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