Input is the term denoting either an entrance or changes which are inserted into a system and which activate/modify a process . It is an abstract concept, used in the modeling , system(s) design and system(s) exploitation. It is usually connected with other terms, e.g. , input field, input variable, input parameter, input value, input signal, input device and input file . Without instructions and information to tell it what to do, the computer cannot do anything. Human programmers must write instructions for the computer. They need to have a way to send their instructions into the computer so that it knows what to do. This is the purpose of input hardware. The term input simply means to put data into the computer. You will read and hear this term often in connections with computers. Sometimes input is referred to as data entry.
Process (computing) , a computer program or an instance of a program running concurrently with other programs. In computing, a process is an instance of a computer program , consisting of one or more threads , that is being sequentially executed  by a computer system that has the ability to run several computer programs concurrently .
A computer program itself is just a passive collection of instructions, while a process is the actual execution of those instructions. Several processes may be associated with the same program; for example, opening up several instances of the same program often means more than one process is being executed. In the computing world, processes are formally defined by the operating system (OS) running them and so may differ in detail from one OS to another.
A single computer processor executes one or more (multiple) instructions at a time (per clock cycle), one after the other (this is a simplification; for the full story, see superscalar CPU architecture ). After the instructions and information have been entered, the computer is ready to work. The place where it does its work is called the processor. The processor does several jobs. It receives the information that has been entered. It "remembers" or stores information. It also processes the data in some way. The processor is made up of two parts: the central processing unit (CPU) and main storage.
Some of the earlier computers used a method of main computer storage called magnetic core memory. Magnetic core memory has now largely been replaced by semiconductor memory, which is faster and smaller. Still, there is a problem with some types of semiconductor memory. When the power is turned off, all of the information stored in semiconductor memory is lost. So there is a need to store information outside the computer's memory. Devices that store data outside the computer as called secondary storage devices.
After the computer has finished processing data, it needs to have some way of sending its work back to the operator. Otherwise, we would have no way of knowing what the computer had done and computers would be useless to us. Sending the data from the computer back to the operator is referred to as outputting data.
A number of devices can be used to output data. The kind of device that the operator chooses depends on what kind of output she or he needs. If the operator needs only to see the data, then a terminal with a CRT/screen can be used. If the operator what to have a permanent copy, usually printed on paper, then a printer can be used.