Object code

Computers use special code to work. A tool makes this code. It is called object code. This code is a set of steps. It tells the machine what to do.

Think of it like a puzzle piece. One piece is not a whole picture. You must join many pieces together. A tool called a linker joins them. It makes a complete program.

This code is part of a bigger plan. It can live in a library file. It can also be in an executable file. The computer can then run it. It is how programs start working.

Computers need special instructions to work. These instructions are called object code. A tool makes this code. We call these tools compilers or assemblers. The code is a set of steps. These steps are often in machine code. Machine code is a language of binary. Binary uses numbers to talk to the computer.

Think of object code like a puzzle piece. One piece is not a whole picture. You must join many pieces to finish the job. A tool called a linker joins these pieces. The linker takes object files and makes an executable file. An executable file is a complete program.

Object code is not a full program yet. It is just one part. It may have placeholders in it. These are spots for the linker to fill in. The linker uses these spots to connect everything. The code also has info about memory. This helps the linker move the code to the right place. This way, many parts can work as one big program.

Computers need instructions to do any job. One type of instruction is called object code. This code is the result of a special process. A tool called a compiler or an assembler makes it. It is a sequence of statements or instructions. These instructions are often in machine code. Machine code is a binary language. This code is the goal of the compiling process. It is a very important part of making software.

How does this work step by step? First, a tool like an assembler takes code. It converts assembly code into machine code. This machine code is the object code. This code is just one part of a program. It is not a complete program yet. It may have placeholders or offsets inside it. These are spots for the linker to fill in later. The linker uses these spots to connect everything together.

Learning about these tools helps us see how programs grow. Early sources even called the original code a "subject program." This shows how the object code was the final goal. We use different tools to reach that goal. An assembler turns assembly code into machine code. Some compilers can even skip the object step. They can go straight to making an executable file. This shows how much the process can change.

There are many specific facts about these files. An object file is a portion of machine code. It is for one particular library or module. It is not yet linked into a complete program. An object file usually starts at a specific memory location. This location is often zero. The file contains info about instructions for memory. This helps the linker move the code later. This is how the linker combines multiple files.

Think of object code like a single puzzle piece. One piece is not a whole picture. You must join many pieces to finish the job. A tool called a linker joins these files. It can join object files and library files. This creates an executable file or a library file. An executable file is a program that can run. It is like building a big machine from small parts. All these parts must fit together perfectly.

In the world of computing, object code is a vital intermediate product. It is the result of a process called compilation or assembly. You can think of it as a bridge between human ideas and machine actions. Object code consists of a sequence of instructions in a computer language. Most often, this is machine code, which is a binary language. It can also be an intermediate language like register transfer language (RTL). This code represents the goal or result of the compiling process.

To understand how this works, we must look at the conversion process. A programmer starts with source code to write instructions. Then, a tool called an assembler or a compiler takes that code. An assembler converts assembly code into machine code, which becomes the object code. This object code is a portion of machine code. However, it is not yet a complete, runnable program. It is the machine code for one specific module or library.

Object code has unique features that distinguish it from final machine code. While machine code can be executed directly by a CPU, object code cannot. This is because object code contains placeholders or offsets. These are specific spots that are not found in a completed program. These placeholders allow for future connections. The code has jumps and inter-module references that are partially parametrized. This means they are not yet fully defined. A tool called a linker must fill these parameters in later.

There are different ways these files are organized and used. An object file is typically one part of a larger system. It might represent one particular library or one specific module. To be useful, object code must be placed into a specific type of file. It can be placed in an executable file or a library file. It can also remain as an object file itself. These files are eventually combined to make the final product.

The linker plays a crucial role in managing these files. A linker takes several object files and library files and joins them. This process generates either an executable file or a library file. An executable file is a complete program that a computer can run. During this process, the linker handles memory and connections. An object file is assumed to begin at a specific location in memory. This starting location is often zero.

Linking also involves a process called relocation. Object files contain information regarding instructions that reference memory. The linker uses this information to move the code around. This allows the linker to relocate the code when combining multiple files. This step is necessary to fit all the pieces into a single, working program. Without relocation, the different modules might conflict with each other in the computer's memory.

Historically, the way we describe these processes has changed. In early computing sources, the original source code was called a "subject program." This terminology shows that the object code was seen as the ultimate goal. Today, we use more specific terms like compiler and assembler. We also know that some tools can skip steps. Some assemblers and compilers can assemble directly to machine code. This allows them to produce executable files without using an object intermediary step.