Definition:
System:
A
collection or combination of several units in a proper (systematic) way such
that we can get our set goal/objectives. E.g.
A traffic system, A system of courier, A
system of school, a computer system etc.
Computer system:
In
very simple way we can understand its meaning. To achieve a goal or get solved
our problem we combine many integrated components
properly which in total is called “computer system”. It is obviously that a
computer system can have major components like, hardware, software and
liveware. If we go deeply we can have many other sub-components. Like computer,
we have other systems, Railway, Banking, Courier, Airlines system with computerized system.
Meaning of computer
architecture and computer organization: Let’s see following table to understand.
computer Architecture:
|
computer organization:
|
1.It says about design.
|
1.It says
about association.
|
2. It
comes first.
|
2.It comes
after design.
|
3. It is time consuming task.
|
3. It
is not.
|
4.The main target
is “HOW”.
|
4.The main target
is “what you want to do on computer”.
|
5.It is self dependent or on designers.
|
5. It is on architecture and
can not do anything without architecture.
|
6. A layout
or blueprint before construction of
house.
|
6. Organization reveals its performance with
placement of different components like
brick,cement etc.
|
7. It is visible (intial phase)
|
7. It is not visible.( we can not know how process is
going on inside)
|
8.It is more expensive to design.
|
9. It is also expensive ,but comparatively low.
|
For example, if you buy a home, the empty house is a result of the architecture. But when you move in and fill it with your stuff, your stuff and where you put it is the organization.
Digital diagram/architecture of computer:
The
typical diagram of computer architecture with different unit is shown below.
The explanation of every unit is given below.
Input Devices:
An input device is any peripheral (piece of
computer hardware equipment) used to provide data and instructions to the
computer. Input Devices Include the Mouse, Keyboard, Touch Screen Monitor,
Scanner, Track Pad, Microphone, Joystick, Web
Camera. These also can be used to activate
the applications on screen.
FUNCTIONS
OF CONTROL UNIT
Definition:
The control unit maintains/controls entire system.It works
like in same way as our brain does. It follows the order within
the computer system and
directs the flow
of traffic(operations) and
data and instructions.
○ It carries
out many tasks such as encoding,decoding, fetching.
○
It handles the execution and finally storing
the results.
○
It controls the execution
of instructions in a sequential order.
○
It guides the flow of data through the different parts of the computer.
○
It regulates the time controls of the processor.
ALU functions:
Definition:
A unit which carries
out all necessary operations and takes
decisions. It has following major
roles.
●
The arithmetic and logic unit
(ALU) performs all arithmetic operations (addition, subtraction,multiplication, and division)
●
responsible for logic operations.Logic operations
test various conditions
encountered during processing and allow for different actions to be taken based
on the results.
●
it fetches/stores all data from/to registers.
Further, it has one more unit called
“Register” which it uses more frequently. It is simply a location inside
microprocessor which holds data/instructions/outputs for a while. It has many
types like, MAR (memory address register), MBR (memory buffer register), program counter, Accumulator register,Instruction Register etc.
Storage unit:
Definition:
This unit (or a device) which system uses to store
data or instruction or applications may be for short (temporarily) time or long
time(permanently) is called storage unit.It stores information (i.e.
instruction data intermediate and final result of processing) that arrives via
the input unit or processing unit for a while or for longer time or so that
this information is made available to the appropriate unit whenever needed.
It has two types:
1.
Primary (main memory or internal memory or memory)
2.
Secondary (backup or mass)
Primary memory:
The main functions
of “main memory”
are:
` 1. to store instruction which is under process
2. to store data which is being processed 3.to store instruction waiting
to be processed.
4. to store
data waiting to be processed.
5.
to store result and to use it for further process.
6. to store programs/applications,utilities used by computer
to run smoothly. The primary memory
has further two types. They are:
1. RAM
2.
ROM
Secondary memory: The main function
of secondary is to store huge amount of data/instructions,softwares etc and
for everything for longer use.
Suppose, we want:
■
to store unlimited data
■
to back up our valuable data
■
to analyze the data for future
or decision taking
and not our data to be volatile etc
For
these all we use secondary storage.
Output unit: A display/
unit which shows or displays everything like, on going processes,activated
applications, what a user is entering , what is the output, what is the problem
etc. This part is major part of system. For example, Monitor, plotter, printer
etc. The purpose of these devices is to translate the machine's response to a
usable form for the computer user. It can
be categorized into two parts namely soft and hard output.
How digital architecture works?
To solve
our problem we enter two things namely
data and instructions. The data and
instructions are entered via an input unit like
keyboard or mouse under the control of control unit. Having entered, the data
is stored inside main memory (RAM). The data resides there until the whole
process is over. From ‘RAM’ the data to be processed under different
instruction are taken into another location called ‘Register’. Here the
data/instruction or output is stored instantly by ALU. If anything more needed
then it (may be by CU) asks with RAM or secondary media. The temporary output
is displayed then on screen. If the user asks/thinks to store the output
permanently then the computer takes that output
from main memory to hard disk or any other media for future use.So, in this way
we can see how different unit/s work together
to solve our problem.
Details
about memory storage unit):
The typical
diagram of all storage units
can be shown in following format.
Primary memory:-
RANDOM ACCESS MEMORY (RAM).—
RAM, also called
read/write memory, is
like a chalkboard. You can write
notes, read them, and erase them when you no longer need them. In the computer,
RAM is the working
memory. Data can be read
(retrieved) from or written (stored) into RAM just by giving the computer the
address of the RAM location where the data is stored or is to be stored. When the data is no longer needed,
you can simply write over it. This allows you to
use the storage again for something else. RAM which stands for “Random Access
Memory” , here, ‘Random’ means frequently writing and reading from and to. It
can handle/store contents as long as power is on. As the power cuts off it
loses everything. Due to this behavior
it is also called “Volatile memory”.
It has following major
responsibilities.
` 1. to store instruction which is under process
2. to store data which is being processed 3.to store instruction waiting
to be processed.
4. to store
data waiting to be processed.
5.
to store result and to use it for further process.
6. to store programs/applications,utilities used by computer
to run smoothly. The primary memory
has further two types. They are:
1. SRAM
2.
DRAM
SRAM
|
DRAM
|
a)It stores as long as power is on. It is static.
|
a)it stores for very short time; not the matter whether power is on or off. It is dynamic.
|
b)
Transistors are
used.
|
b)
Memory cells
are made up
of small tiny capacitors
|
c)
It is less dense.
|
c)
It is dense in
nature.
|
d)
Charge doesn't leaks
from transistors.
|
d)
Charge leaks from
capacitor.
|
e)
It doesn't need
periodic refreshing.
|
e)
It needs periodic
refreshing.
|
f)
It is more expensive.
|
f)
It is less expensive.
|
g)
it is faster than
DRAM
|
g)
it is slower than
SRAM
|
READONLY MEMORY (ROM).— Just
think for a while, from where computer gets instructions during start up, do
we? Or do we enter any instructions in beginning, no. It is due to programs
stored in a small chip called “ROM”.It is useful to have often used
instructions, such as those used to bootstrap (initial system load or start up)
the computer or other specialized programs, permanently stored inside the
computer. The memory that enables us or computer to do this without the
programs and data being lost even when the computer is powered down
or off is readonly memory (ROM). The contents
are readable as many as a user or computer wants but
can not be changed. It is non-volatile means it does not dependent on power or instructions do not get lost after power cut off.
It has following types.
PROGRAMMABLE READONLY MEMORY (PROM).— A type
of ‘ROM’ which we can buy already programmed by the manufacturer
or in a
blank state. Using a blank PROM
and a device (PROM programmer) designed to write (burn) a program into PROM, we can enter
any program into the memory. However, we cannot make any changes to the program
once it has been written into PROM. But, PROM does provide
flexibility not available with ROM. Of course, we must be sure the program
is error free before it is written
into PROM.
ERASABLE PROGRAMMABLE READ
ONLY MEMORY (EPROM).—
The erasable programmable readonly memory (EPROM) was developed to overcome the drawback of PROM. We can write programs at our command/activity using a special device. The big
difference with EPROM is that we can erase it if and when the need arises.
The data and
programs can be retrieved
many times. If you want to reprogram
memory, you first erase the
EEPROM with a
burst of ultraviolet light by taking it out and through a
small window. This not only enables
you to reprogram when requirements change, but also,
you can erase
and write the program again
if a mistake is made while programming the EPROM. It it mostly
done by skilled
hardware engineers.
Cache memory:-
A high speed storage area or location which is used to store data/information.Normally we say it is a part of RAM or simply SRAM. It uses special high-speed
storage mechanism. This memory can be seen in fixed form between processor and RAM or in some inside the processor
and provides frequently used data.The CPU uses cache memory
to store instructions that are repeatedly
required to run programs, improving overall system speed.
1. Internal cache (L1): An L1 (level 1) cache is on the same chip as the microprocessor i.e. it exists inside the microprocessor chip. so It can be said internal to processor.
Suppose, we have opened some applications or going to activate. As we open that the
Def:
This unit is high speed storage area existing
inside microprocessor. It can hold different things like operand, operator,
instruction,output etc. It can have different types:
1. Memory
Address Register (MAR): This register
holds the memory
addresses of data
and instructions.
2. Memory Buffer Register (MBR): This register
holds the contents of data or instruction read from, or written
in memory.
Cache memory:-
A high speed storage area or location which is used to store data/information.Normally we say it is a part of RAM or simply SRAM. It uses special high-speed
storage mechanism. This memory can be seen in fixed form between processor and RAM or in some inside the processor
and provides frequently used data.The CPU uses cache memory
to store instructions that are repeatedly
required to run programs, improving overall system speed.
There are two types.
1. Internal cache (L1): An L1 (level 1) cache is on the same chip as the microprocessor i.e. it exists inside the microprocessor chip. so It can be said internal to processor.
2. External cache(L2):- An L2 (level 2) is usually a separate static RAM (SRAM) chip. The main RAM is usually a dynamic RAM (DRAM) chip. It is external to processor and lies in middle part of processor and RAM.
Some other processors L3 can have cache built on it.
How it works:-
Suppose, we have opened some applications or going to activate. As we open that the
Buffer:-
It is an area or a part of RAM used by system to
store input,output temporarily. It is used before the data is used by the
system. For example, when we give a command to printer to print, the data or
document first is stored in buffer area an then transferred to printer. when
you download an audio or video file from the Internet, it may load the first
20% of it into a buffer and then begin to play. While the clip plays back, the
computer continually downloads the rest of the clip and stores it in the
buffer. Because the clip is being played from the buffer, not directly from the
Internet, there is less of a chance that the audio or video will stall or skip
when there is network congestion.
let’ see following diagram to be more clear about reading,writing,
storing from and to
RAM | ROM |
1. It is used for writing as well as reading.
|
1 it is used for only reading.
|
2. It holds the contents only if there is power.
|
2. It holds the contents in presence /absence of
power. |
3.it is used after startup.
|
3. it is used mostly during startup.
|
4. it has more storage capacity.
|
4. less storage capacity.
|
5.It is not expensive.
|
5. it is expensive.
|
6. Mostly, it is in unfixed form.
|
6. it is in fixed form.
|
7. two types namely SRAM and DRAM.
|
7. Many types PROM, EPROM and EEPROM
|
Firmware
(microcode or microprogram):
Just think for a while, from where computer gets
instructions during start up, do we enter? Or do we enter any instructions in
beginning, no. It is due to programs
stored in a small chip called “ROM”.
Only
the computer manufacturer can install these
programs into ROM, and, once installed,
they cannot be changed. Yeah, these programs
are called “Firmware”.
Firmware is a software program permanently etched
into a hardware device such as a keyboards, hard drive, BIOS, or video cards.
It is programmed to give permanent instructions to communicate with other
devices and perform functions like basic input/output tasks. Firmware is
typically stored in the flash ROM (read only memory) of a hardware device. It can be erased and rewritten.Without firmware, a hardware
device would be nonfunctional. Think about
your remote control, think about
mobile phone, etc. they all work by using firmware. It can have different level
like,:
1. Low Level Firmware:
2.
High Level Firmware:
3.
Subsystems:
Concept of Microprocessor design: We can use two types of technology to design processor. They are RISC and CISC.
CISC
|
RISC
|
1. It has complex (more)instructions.
|
1. It has fewer
instructions.
|
2.It has
very complex architechture.
|
2. It has simple
architecture.
|
3.It is slow and uses more power.
|
3. It is fast and uses less power.
|
4.It uses more no. of transistors.
|
4.It uses
less no. of transistors.
|
5.It is expensive to produce.
|
5.It is cheaper to produce.
|
6.It utilizes more no. of cycles.
|
6. It utilizes less
no. of cycles.
|
Concept of “BUS”:
To have a communication between several units our computer uses many or a set of wires,which is called Bus.
Or
We can say a medium or a physical path used by
system to carry signal,data,instruction from one unit to another. It can be
considered as a highway on which data travels with high speed
inside the system.
It is measured in MHZ.
The diagram
of bus architecture is shown
below.
Types and
explanation:
1.
Address bus: A bus which
>carries the address
of data,device etc
> is unidirectional (just like one lane).
>can have many wires (8 or 16 or more)
2.
Control Bus: A bus which
>carries controlling signal incoming from control unit
>carries signal like reading or writing or interpreting.
>is one way(unidirectional)
3.Data bus:A type of bus which
3.Data bus:A type of bus which
> carries data to/from different units
>is bidirectional
>can have 16/32
wires to carry
data.