1.1 What is a computer?
A computer is a data processing machine which
is operated automatically under the control of a list of instructions (called a
program) stored in its main Memory.
1.2 What is a computer system?
• A computer system consists usually of a
computer and its
peripherals.
• Computer peripherals include input devices, output
devices,
and secondary memories
2.The Computer Level Hierarchy
The machine
built from a hierarchy of levels, in which each level has a specific function
and exists as a distinct hypothetical machine. We call the hypothetical
computer at each level a virtual machine. Each level s virtual machine executes
its own particular set of instructions, calling upon machines at lower levels
to carry out the tasks when necessary. As well as how these layers are
implemented and interface with each other. Figure (3) shows the commonly
accepted layers representing the
abstract virtual machines.