Opcode facts for kids

An opcode is like a special command that tells a computer what to do. Think of it as a single word that gives the computer a specific instruction. When computers run programs, they use these opcodes to understand each step.

Every instruction a computer follows usually has two main parts: the opcode (the command) and the operands (the details for the command). For example, if the opcode is "add," the operands might tell the computer *what* numbers to add together.

What Opcodes Do

Opcodes are used for many different tasks inside a computer. They can tell the computer to:

• Add numbers together.
• Move information from one part of the computer's memory to another.
• Stop a program.
• And hundreds of other things!

Modern computers use many different opcodes to perform all their functions.

How Opcodes Look

Computers understand information in a special language called binary. This means opcodes are stored as sequences of 0s and 1s.

For people, it's hard to read long strings of 0s and 1s. So, opcodes are often shown using hexadecimal numbers. Hexadecimal is a number system that uses 0-9 and A-F. For example, the binary number `10100101` can be written as `A5` in hexadecimal. This makes it easier for people to read and work with. These hexadecimal values are then changed back into binary for the computer to use. Most modern opcodes are at least two hexadecimal characters long, which takes up one byte of storage space.

Opcodes and Different Computers

Opcodes are not the same for every computer. They depend on the computer's specific hardware and design. For example, the command to "STORE" (save information) might be `FA` on one computer and `02` on another. Some computers might not even have certain opcodes.

There are two main ways computers are designed regarding their instruction sets (the list of all possible opcodes):

• Reduced Instruction Set Computer (RISC): These computers have fewer opcodes. This design helps them work faster for simpler tasks.
• Complex Instruction Set Computer (CISC): These computers have many more opcodes. This design helps them work faster for more complicated tasks.

How Programmers Use Opcodes

Most programmers don't work directly with opcodes. If they did, their programs would only work on the exact computer they were made for.

Instead, programmers often use assembly language. This language uses short, easy-to-remember words called mnemonics for each opcode. A special program then translates these mnemonics into the binary opcodes the computer understands.

Even more commonly, programmers use high-level programming languages (like Python or Java). These languages are much easier for humans to read and write. Another program then translates the high-level code step-by-step into simpler code, until it finally becomes the machine code (with opcodes) that the computer can run. This way, a program can work on many different types of computers.

See also

In Spanish: Código de operación para niños