|Types of code|
|Notable compilers & toolchains|
In computing, executable code, executable file, or executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instructions",as opposed to a data file that must be parsed by a program to be meaningful.
The exact interpretation depends upon the use. "Instructions" is traditionally taken to mean machine code instructions for a physical CPU.In some contexts, a file containing bytecode or scripting language instructions may also be considered executable.
Executable files can be hand-coded in machine language, although it is far more convenient to develop software as source code in a high-level language that can be easily understood by humans. In some cases, source code might be specified in assembly language instead, which remains human-readable while being closely associated with machine code instructions. The high-level language is compiled into either an executable machine code file or a non-executable machine code object file of some sort; the equivalent process on assembly language source code is called assembly. Several object files are linked to create the executable. Object files -- executable or not -- are typically stored in a container format, such as Executable and Linkable Format (ELF).This gives structure to the generated machine code, for example dividing it into sections such as .text (executable code), .data (initialized global and static variables), and .rodata (read-only data, such as constants and strings).
In order to be executed by the system (such as an operating system, firmware, or boot loader), an executable file must conform to the system's application binary interface (ABI).
e_entry field, which specifies the (virtual) memory address at which to start execution. In the GCC (GNU Compiler Collection) this field is set by the linker based on the
Executable files typically also include a runtime system, which implements runtime language features (such as task scheduling, exception handling, calling static constructors and destructors, etc.) and interactions with the operating system, notably passing arguments, environment, and returning an exit status, together with other startup and shutdown features such as releasing resources like file handles. For C, this is done by linking in the crt0 object, which contains the actual entry point and does setup and shutdown by calling the runtime library.
Executable files thus normally contain significant additional machine code beyond that directly generated from the specific source code. In some cases it is desirable to omit this, for example for embedded systems development, or simply to understand how compilation, linking, and loading work. In C, this can be done by omitting the usual runtime, and instead explicitly specifying a linker script, which generates the entry point and handles startup and shutdown, such as calling
main to start and returning exit status to the kernel at the end.
In computing, the Executable and Linkable Format, is a common standard file format for executable files, object code, shared libraries, and core dumps. First published in the specification for the application binary interface (ABI) of the Unix operating system version named System V Release 4 (SVR4), and later in the Tool Interface Standard, it was quickly accepted among different vendors of Unix systems. In 1999, it was chosen as the standard binary file format for Unix and Unix-like systems on x86 processors by the 86open project.
A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally describes what is required in a JVM implementation. Having a specification ensures interoperability of Java programs across different implementations so that program authors using the Java Development Kit (JDK) need not worry about idiosyncrasies of the underlying hardware platform.
In computing, a linker or link editor is a computer system program that takes one or more object files generated by a compiler or an assembler and combines them into a single executable file, library file, or another 'object' file.
In computer science, an interpreter is a computer program that directly executes instructions written in a programming or scripting language, without requiring them previously to have been compiled into a machine language program. An interpreter generally uses one of the following strategies for program execution:
In computer software, an application binary interface (ABI) is an interface between two binary program modules; often, one of these modules is a library or operating system facility, and the other is a program that is being run by a user.
ScriptBasic is a scripting language variant of BASIC. The source of the interpreter is available as a C program under the LGPL license.
The Portable Executable (PE) format is a file format for executables, object code, DLLs and others used in 32-bit and 64-bit versions of Windows operating systems. The PE format is a data structure that encapsulates the information necessary for the Windows OS loader to manage the wrapped executable code. This includes dynamic library references for linking, API export and import tables, resource management data and thread-local storage (TLS) data. On NT operating systems, the PE format is used for EXE, DLL, SYS, and other file types. The Extensible Firmware Interface (EFI) specification states that PE is the standard executable format in EFI environments.
Bytecode, also termed portable code or p-code, is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references that encode the result of compiler parsing and performing semantic analysis of things like type, scope, and nesting depths of program objects.
In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subroutines, classes, values or type specifications. In IBM's OS/360 and its successors they are referred to as partitioned data sets.
In computer science, self-modifying code is code that alters its own instructions while it is executing – usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code, thus simplifying maintenance. Self-modification is an alternative to the method of "flag setting" and conditional program branching, used primarily to reduce the number of times a condition needs to be tested. The term is usually only applied to code where the self-modification is intentional, not in situations where code accidentally modifies itself due to an error such as a buffer overflow.
Execution in computer and software engineering is the process by which a computer or virtual machine executes the instructions of a computer program. Each instruction of a program is a description of a particular action which to be carried out in order for a specific problem to be solved; as instructions of a program and therefore the actions they describe are being carried out by an executing machine, specific effects are produced in accordance to the semantics of the instructions being executed.
A fat binary is a computer executable program or library which has been expanded with code native to multiple instruction sets which can consequently be run on multiple processor types. This results in a file larger than a normal one-architecture binary file, thus the name.
Mach-O, short for Mach object file format, is a file format for executables, object code, shared libraries, dynamically-loaded code, and core dumps. A replacement for the a.out format, Mach-O offers more extensibility and faster access to information in the symbol table.
In computer programming, an entry point is where the first instructions of a program are executed, and where the program has access to command line arguments.
Dynamic-link library (DLL) is Microsoft's implementation of the shared library concept in the Microsoft Windows and OS/2 operating systems. These libraries usually have the file extension
DRV . The file formats for DLLs are the same as for Windows EXE files – that is, Portable Executable (PE) for 32-bit and 64-bit Windows, and New Executable (NE) for 16-bit Windows. As with EXEs, DLLs can contain code, data, and resources, in any combination.
a.out is a file format used in older versions of Unix-like computer operating systems for executables, object code, and, in later systems, shared libraries. This is an abbreviated form of "assembler output", the filename of the output of Ken Thompson's PDP-7 assembler. The term was subsequently applied to the format of the resulting file to contrast with other formats for object code.
In computing, a dynamic linker is the part of an operating system that loads and links the shared libraries needed by an executable when it is executed, by copying the content of libraries from persistent storage to RAM, filling jump tables and relocating pointers. The specific operating system and executable format determine how the dynamic linker functions and how it is implemented.
This is a comparison of binary executable file formats which, once loaded by a suitable executable loader, can be directly executed by the CPU rather than become interpreted by software. In addition to the binary application code, the executables may contain headers and tables with relocation and fixup information as well as various kinds of meta data. Among those formats listed, the ones in most common use are PE, ELF, Mach-O and MZ.
This article compares the application programming interfaces (APIs) and virtual machines (VMs) of the programming language Java and operating system Android.
In computer science, dynamic software updating (DSU) is a field of research pertaining to upgrading programs while they are running. DSU is not currently widely used in industry. However, researchers have developed a wide variety of systems and techniques for implementing DSU. These systems are commonly tested on real-world programs.