By: Obafemi Babatunde Oluwasanu
3.2.1 Outline the structure of the central processing unit (CPU) including the
functions of the control unit (CU), the arithmetic and logic unit (ALU), primary
memory and address buses.
3.2.2 Outline the meaning of the terms bit (b) and byte (B) and their derivatives.
3.2.3 Outline the meaning of the terms word, register and address and their use in
the storage of data and instructions. The study of specific registers is not
3.2.4 Outline the steps in the machine instruction cycle: fetch, decode, execute
and store. A single processor model is sufficient. The study of a specific CPU is
3.2.5 Outline the characteristics of primary memory and the difference between
volatile and non-volatile memory.
3.2.6 Outline the characteristics of secondary memory and define sequential and
3.2.7 Outline the function of a microprocessor designed to perform one or a
limited number of functions (within a car, washing machine and so on).
3.2.8 Discuss the features, advantages, disadvantages and applications of specific
input and output devices and the media used by each.
3.2.9 Outline recent developments in computer system architecture including
processor architecture, primary memory technologies and secondary memory
What is the basic structure to a CPU?
The CPU is comprised of
five basic parts.
◦ CU(Control Unit)-gets the
instructions to the program
and gives instructions to the…
◦ ALU(Arithmetic Logic Unit)-
computes the stuff.
◦ RAM-the primary memory
used to store information
required to execute
◦ Registers-quick access
memory locations used to do
things such as boot etc. Also,
processor registers are at the
top of the memory hierarchy.
◦ Buses-wires that 1’s and 0’s
travel across. The highway
system to the CPU.
What is a bit and a byte?
Are they the same??
First of all everything in a computer is seen in a
binary representation or 1’s and 0’s.
A bit and a byte are not the same. A bit is a
singe “1” or “0” in machine language. So the
binary number 100101001 is 9 bits long.
Now a byte is a number of bits. Usually 8 bits to
be exact. Therefore, the same binary number
100101001 is 1.125 bytes long.
Lastly bits and bytes are prefixed with the
decimal prefixes because that’s what we
understand. In other words to represent
1,000,000,000,000 bytes you would say 1T bytes
or one terabyte. (just know the prefixes T, G, M,
Word? Isn’t that like a sound
representing an idea?
Word-or “word size” is a fixed group of bits that
are handled together by the machine. It can vary
from machine to machine but in general the sizes
of buses and registers are multiples of the word
size. So if the word size is 10 then the busses
might be able to care 30 at a time.
Registers-are non-volatile memory locations that
store must happen instructions of data. They can
also be accessed quickly.
Address-where something is at in memory or its
index. Addresses are used so that items in
memory can be found more quickly because they
have an index.
What is the machine instruction cycle?
The machine instruction cycle is three basic steps, fetch, decode
Fetch is where the computer gets instructions from the program
and gives them to the decoder. This is a one at a time process.
Decode is where the computer converts the instructions into
machine language(1’s and 0’s remember) and identifies the
processes that need to take place to handle those instructions.
Execute does what it says. It executes or does the processes
that need to be done for the instructions objectives to be
Once each step has done it’s job the instructions are threaded
back up to the fetch where it will say “okay I’m done” to the
Which memory is used first?
The primary memory used by the CPU is the RAM, ROM, and cache
memory and are used to do the normal operations of the computer.
RAM(RandomAccessMemory)-is used to do the “daily” duties of the
computer. It is a volatile type memory which means that it does not
store things permanently but is “renewed” on every restart.
ROM(ReadOnlyMemory)-is used to store things like boot operations and
stuff like that. There is also PROM or ProgramableROM.
Cache Memory is quick access memory usually 2MB now that is used to
lower the latency of references to data in main memory(ram) that is
recently being used.
Virtual Memory is also used as a primary memory source. It’s basically
the concept of writing not recently used data on the RAM to the hard
drive to free up RAM and give the running programs the impression that
they have more memory to work with.
Now which is used second?
Secondary memory is things like DVD, CD, disks, or
Flash and are used to run optional tasks.
Most secondary memory types are non-volatile
memory sources which means that they can store
Also, between the different types each is accessed
differently, either directly or sequentially.
Direct access means that the space is indexed and
can be read from any indexed point.
Sequential access means that it can only be read from
the start or from wherever it was closed at last.
There are multiple uses for secondary memory. They
can be used to store files, games, or anything really
so long as the space is available.
Microprocessors are used in more machines
than just computers. They are used in cars ,
washer machines and other things.
For example in a microwave you could have a
processor that would take the user input of a
time and output an electrical charge to turn
on the microwaves for the set time. It would
also have some sort of RAM or probably a
small cache and register maybe actually so
that it can remember the time and any
What are some of the input and output
devices with on a computer?
And what are they good for?
Some of the input devices used by the
computer are the mouse, keyboard, touch
screen, OCR(optical character recognition),
MICR(magnetic ink recognition), scanners,
LCD, panels, speech recognition, sensors,
digital cameras, graphics tablets, printers,
plotters, monitors, robotics, sound.
All these things can be used to do different
things. The main objective though is to make
the access to the computer and it’s abilities
What are some of the recent
developments in Computer
There are always new improvements being
developed in computer architecture and you
have to live a life like Patrick to keep up with
them all. And that’s nearly impossible.
Examples are vista now has support for flash
memory to be used for virtual memory uses.
Also multi-cores are advancing and CPU
caches are getting bigger. For instance some
say the new processors could have 6MB of
I love IB computer science because…
◦ It’s teaching me a lot about computer science that I
didn’t know before.
◦ It’s making me a harder worker.
◦ It’s making me smarter.
◦ It’s paving a path for my future.
◦ And it provided a way for Taylor Devnich to teach
the class and me K-maps. :D