<P> A computer is a machine that manipulates data according to a set of instructions called a computer program . The program has an executable form that the computer can use directly to execute the instructions . The same program in its human - readable source code form, enables a programmer to study and develop a sequence of steps known as an algorithm . Because the instructions can be carried out in different types of computers, a single set of source instructions converts to machine instructions according to the central processing unit type . </P> <P> The execution process carries out the instructions in a computer program . Instructions express the computations performed by the computer . They trigger sequences of simple actions on the executing machine . Those actions produce effects according to the semantics of the instructions . </P> <P> Computer software or just "software", is a collection of computer programs and related data that provides the instructions for telling a computer what to do and how to do it . Software refers to one or more computer programs and data held in the storage of the computer for some purposes . In other words, software is a set of programs, procedures, algorithms and its documentation concerned with the operation of a data processing system . Program software performs the function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software . The term was coined to contrast with the old term hardware (meaning physical devices). In contrast to hardware, software is intangible . Software is also sometimes used in a more narrow sense, meaning application software only . </P> <P> Application software, also known as an "application" or an "app", is a computer software designed to help the user to perform specific tasks . Examples include enterprise software, accounting software, office suites, graphics software and media players . Many application programs deal principally with documents . Apps may be bundled with the computer and its system software, or may be published separately . Some users are satisfied with the bundled apps and need never install one . </P>

Which of tha following is an input device in computer