1.Define input and differentiate among a program command and user respond?

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 port, input device and input file (file format).
Input may refer to:

• Advice (opinion), an opinion or recommendation offered as a guide to action, conduct.
• Information, any data entered into a computer or data processing system, see input output
• The act of entering data into a computer or data processing system (see Input/output).
• Input device, any peripheral (piece of computer hardware equipment) used to provide data and control signals to an information processing system (such as a computer)
• Stimulus (physiology), a detectable change in the environment that influences an activity of an organism
• Power consumption, an amount of power used by a system.
• International Public Television Screening Conference, an international public television organization
• In economics, a factor of production, a resource employed to produce goods and services.

                 
 Command-line interface (CLI) is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks. This text-only interface contrasts with the use of a mouse pointer with a graphical user interface (GUI) to click on options, or menus on a text user interface (TUI) to select options. This method of instructing a computer to perform a given task is referred to as "entering" a command: the system waits for the user to conclude the submitting of the text command by pressing the "Enter" key (a descendant of the "carriage return" key of a typewriter keyboard). A command-line interpreter then receives, parses, and executes the requested user command. The command-line interpreter may be run in a text terminal or in a terminal emulator window as a remote shell client such as PuTTY. Upon completion, the command usually returns output to the user in the form of text lines on the CLI. This output may be an answer if the command was a question, or otherwise a summary of the operation.
The concept of the CLI originated when teletypewriter machines (TTY) were connected to computers in the 1950s, and offered results on demand, compared to batch oriented mechanical punched card input technology. Dedicated text-based CRT terminals followed, with faster interaction and more information visible at one time, then graphical terminals enriched the visual display of information. Currently personal computers encapsulate all three functions (batch processing, CLI, GUI) in software.
The CLI continues to co-evolve with GUIs like those provided by Microsoft Windows, Mac OS and the X Window System. In some applications, such as MATLAB and AutoCAD, a CLI is integrated with the GUI, with some benefits of both.

Courtesy of: Wikipedia "The free Encyclopedia"