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Execution in computer and software engineering is the process by which a computer or virtual machine interprets and acts on the instructions of a computer program.Each instruction of a program is a description of a particular action which must be carried out, in order for a specific problem to be solved.
The execution model specifies the behavior of elements of the language. By applying the execution model, one can derive the behavior of a program that was written in terms of that programming language. For example, when a programmer "reads" code, in their mind, they walk through what each line of code does.
In computer science, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instructions", [2] as opposed to a data file that must be interpreted by an interpreter to be functional.
While a computer program is a passive collection of instructions typically stored in a file on disk, a process is the execution of those instructions after being loaded from the disk into memory. Several processes may be associated with the same program; for example, opening up several instances of the same program often results in more than ...
The kernel creates a process control block when a computer program is selected for execution. However, an executing program gets exclusive access to the central processing unit only for a time slice. To provide each user with the appearance of continuous access, the kernel quickly preempts each process control block to execute another one.
The runtime environment includes not only accessible state values, but also active entities with which the program can interact during execution. For example, environment variables are features of many operating systems, and are part of the runtime environment; a running program can access them via the runtime system. Likewise, hardware devices ...
For example, a conditional branch instruction will transfer control if the condition is true, so that execution proceeds to a different part of the program, and not transfer control if the condition is false, so that execution continues sequentially.
For example, more than one user can be executing the same program, with each user having separate copies of the program loaded into memory. With some programs, it is possible to have one copy loaded into memory, while several users have shared access to it so that they can each execute the same program-code. Such a program is called re-entrant.