The two components shown are the Control Unit and the
Arithmetic Logic Unit.
The CU does not execute instructions or do maths.
The ALU does addition, subtraction, multiplication and
The ALU does equal, less than or greater than logical
Registers are temporary storage areas for instructions or
data, and there advantage over normal memory is speed.
Main memory is also known as primary storage, primary
memory, main storage and internal storage.
Memory stores programs and data. (Or 1's and 0's.)
The hardware that controls the flow of data from secondary
storage to memory is the secondary storage controller. In
the case of IBM and compatible computers, the application
makes a request to DOS, which requests the BIOS, which
requests the controller, which gets the information, gives
it to the BIOS, which in turn gives it back to DOS which
then gives it to the application. (However, many programs
"cut the crap" and either ask BIOS (skipping DOS) or access
the hardware themselves - it's faster and less "clunky".)
The CPU's internal clock sychronizes every action within the
Microcode is the instructions contained within the CPU that
actually tell it what to do, and when.
A binary system is a two-state system.
a bit is one single value - a 0 or a 1. It got its name from
the words binary digit.
A character is represented by 8 bits, collectively called a
1024 bytes is called a kilobyte (Kb) - this is 2 to the 10th power (2^10).
1048576 bytes is called a megabyte (Mb) - this is 2 to the 20th power (2^20).
A computer word is the number of bits that constitutes a
common unit of data.
The bigger the word, the fast the processing, the greater
the memory that can be addressed, the richer the instruction
A data bus is a series of wires arranged meaningfully inside
the computer, carrying information to each of the
Volatile means that unless the charge is continually
refreshed then it will suffer a severe case of amnesia.
Memory is usually volatile; secondary storage is permanent
LSI stands for Large Scale Integration and VLSI stands for
Very Large Scale Integration.
RAM is (usually - except for SRAMs) volatile.
EPROM stands for Eraseable Programmable Read Only Memory.
millisecond = 1000th of a second
microsecond = 1000000th of a second
nanosecond = 1000000000th of a second
picosecond = 1000000000000th of a second
Serial processing computers only have one processor;
parallel computers have two or more.
The speed of a computer can be increased by adding processors, reducing the
instruction set, reducing the distance to be travelled by
the electrical signals, increasing the bit size, or changing the
material that the chip is made of (eg. switch to Gallium Arsenide).
Gallium Arsenide is better that Silicon for computer chips
because while GaAs has all the properties of Silicon
necessary for the computer to work, it conducts electricity
at a far greater rate. Its main drawback is its cost - it is
too expensive to use right now.