A computer is a machine which helps us to calculate, simulate and store different scenarios. For example, in order to write an e-mail, instead of paper and pen first we use a software (or program) called wordprocessor which helps us enter sentences through keyboard (Input), computer's screen (output) to read, and modem (output/input) to send it to a distant relative, friend, etc.
The mechanism to simulate a regular mail into an e-mail, gave us a very fast and much cheaper medium to communicate (not a simulation anymore). Same way, using computers we can simulate other things over which we do not have any control, for example weather, behaviour of atomic bomb, behaviour of a deadly virus, Earthquake, a innovative design for a new auto, airplane, machine, etc.
Any computer has five parts Input, Output, CPU, Memory, disk (storage) . Input is things like mouse, keyboard, modem. Output is computer screen, printer. CPU or central processing is brain of the computer which controls and execute all calculations, manipulations and output. Memory (RAM)is a temporary storage to be used by CPU when doing calculations, etc. Think of it as a scratch pad for CPU. Disk is permanent storage, on which all the software and data is stored.
When you turn on your computer, BIOS (or basic input output system) which resides on CMOS (complimentary Metal Oxide semiconductor,a type of chip) has small coded software written on it which tells CPU to read the next instruction from sector n of disk x. This next instruction loads the operating system
