Executables are files containing machine code instructions that a computer can directly execute. These files are the end result of compiling and linking source code written in programming languages like C, C++, or Rust. Executables are platform-specific, meaning an executable file created for one operating system (e.g., Windows) won’t run on another (e.g., Linux) without compatibility layers. They form the foundation of software distribution and execution, turning human-readable code into actionable instructions for the CPU.
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Key Characteristics of Executables
1. Binary Format:
Executables consist of binary data that the operating system loader interprets and executes.
2. Platform-Dependency:
Executables are often tailored to specific operating systems and processor architectures.
3. Headers and Metadata:
Executable files include metadata like entry points, segment information, and symbols necessary for execution.
4. Self-Sufficient:
Contains all the compiled instructions, and sometimes resources, needed to run a program.
Types of Executable Files
1. Windows: .exe (Executable File), .dll (Dynamic Link Library).
2. Linux/Unix: ELF (Executable and Linkable Format).
3. macOS: Mach-O Format.
Compilation Process to Create an Executable
1. Source Code: Written in high-level programming languages.
2. Compilation: Source code is converted into object code by a compiler.
3. Linking: Combines object code with libraries to produce an executable.
4. Loading: The operating system loads the executable into memory for execution.
Code Example: Creating an Executable in C
#include <stdio.h>
int main() {
printf(“Hello, World!\n”);
return 0;
}
Compilation Steps (Linux):
gcc -o hello hello.c
./hello
Output:
Hello, World!
The gcc command compiles hello.c into an executable named hello.