Tab Electronics Guide to Understanding Electricity ... - Sciences Club

Computers
363
Figure 14-1
Block diagram illustrating
the basic sections
of a computer.
Input
Input
data bus
Input/Output address bus
CPU
Output
data bus
Output
Input
devices
Memory
address
bus
Memory
data bus
Output
devices
Memory
location. The output section accepts the digital information from the CPU,
converts the information into a usable form, and routes it to the appropriate
output device.
The analytical part of a computer is called the central processing unit
(CPU). In the not-too-distant past, CPUs were relatively large printed circuit
boards containing many integrated circuits. In modern computers,
CPU printed circuit boards have been replaced with a single VLSI (very
large-scale integration) chip called a microprocessor.
A microprocessor can be broken down into two main parts: the arithmetic
logic unit (ALU) and the read-only memory.
The ALU controls the logical steps and orders for performing arithmetical
functions. It interacts with the ROM to obtain instructions for
performing redundant operations. The ROM also contains instructions
pertaining to start-up, and to power-loss conditions.
The digital information sent to the microprocessor can also be broken
down into two main types: data and instructions. These two types of digital
information work with the two main parts of the microprocessor to
perform all analytical operations.
Digital information is received at the microprocessor in the form of
digital words, called bytes. In modern computers, a byte consists of 16 or
32 bits of data. A bit (binary digit) is simply a logical level; it can have
only two states, either high or low. All 16 bits, constituting the byte, are
applied to the microprocessor simultaneously. If the byte of information
is an instruction word, it will be interpreted by the instruction code