Download FYJC COMPUTER SCIENCE II Chapter no

FYJC
COMPUTER SCIENCE II
Chapter no -2
Logic gates and sequential circuits
Logic GatesDefinition -The logic gate is an electronic circuit, which has one or many inputs
and only one output with some logic applied to it. The output and input is
expressed in terms of binary 0 &1.
Logic gates can be constructed by using simple switches, relays, vaccume
tubes, transistors, diodes etc.
Every logic gate is having some logic i.e (binary 0 and binary 1).truth table which
defines the condition of the gate by using combination of inputs .e in terms of
(1‘s and 0‘s ).The no of possible combination in a truth table in given by 2 n.
i.e n=No of inputs
for eg. If n=2 then 2n =22=4 combination of the input side.
It also consist of Boolean equation which is the logical equation derived for
the output and the input of the logic gate.
Basic
NOT
AND
Universal
OR
NAND
Exclusive/special
NOR
EX-OR
EX-NOR
*Basic Gates1) NOT GATE-(Inverter)
This is a logic gate and the sequential circuit having single input and a
single output. This gate is also called as inverter as it inverts the input.
Truth tableOutput
yA
0
1
Input
A
1
0
Logical expression/equation-
yA
2) AND GATE-This is the logic gate and a sequential circuit having more than
one inputs and only one output. The logic of AND gate is ,if any one of input is
‗0‘ or ‗low‘ the output is ‗0‘ or ‗low‘ and when all the inputs are ‗1‘ or ‗high‘
output is ‗1‘ or ‘high‘. The symbol and truth table of AND gate for 2 inputs and
one output is shown below:
Symbol
Truth table-
Inputs
A
0
0
1
1
Logic expression-:
B
0
1
0
1
Output
y  A.B
0
0
0
1
y  A.B
3) OR Gate-This is a logic gate and a sequential circuit having more than one
inputs and only one output. The logic of OR gate is if any one of the input is ‗1‘ or
‘high‘ output is ‗1‘ or ‗high‘ and when all the inputs are ‗0‘ or ‗low‘ the output is
‗0‘ or ‗low‘ .below table shows the symbol and the truth table for two inputs OR
gate
Symbol
Truth tableInputs
A
0
0
1
1
B
0
1
0
1
Output
y  A B
0
1
1
1
Logic Expression/equation-: y  A  B
4)NAND Gate- This is a logic gate and a sequential circuit having more than one
input and only one output . The logic of NAND gate is when any one input is ‗0‘
or ‘low‘ the output is ‗1‘ or ‗high‘ and when all inputs are ‗1‘ or ‗high‘ the output
is ‗0‘ or ‗low‘. Below shows the symbol and truth table for two inputs NAND gate
Symbol
Truth tableInputs
A
0
0
1
1
Output
y  A.B
1
1
1
0
B
0
1
0
1
Logical equation/expression-:
y  A.B
5) NOR Gate-It is a logic gate and sequential circuit having more than one input
and a single output. The logic of NOR gate is when all the inputs are‘0‘ or‘ low‘
the output is ‗1‘ or ‘high‘ and when tall the inputs are ‗1‘ or ‗high‘ the output is
‗0‘ or ‗high‘.
Symbol
Truth tableInputs
A
0
0
1
1
Output
y  A B
1
0
0
0
B
0
1
0
1
Logical equation/expression-:
y  A B
6) Ex-Or Gate: It is a logic gate and a sequential circuit having more than one
input and only one output. The logic of Ex-Or gate is, when the inputs are
different output is high of 1, and for the same inputs, output is low or 0. Ex-Or
gate is also called as Exclusive Or gate. Below shows the symbol and truth table
for 2 input Ex-Or gate.
Inputs
A
0
0
1
1
Logical expression: y  A  B
Output
y  A B
0
1
1
0
B
0
1
0
1
y  AB  AB
7)Ex-Nor Gate: It is a logic gate and a sequential circuit having more than one
input and only one output. The logic of Ex-Nor gate is, when the inputs are
different output is low or 0, and for the same inputs, output is high or 1. Ex-Nor
gate is also called as Exclusive Nor gate. Below shows the symbol and truth table
for 2 input Ex-Nor gate.
Inputs
A
0
0
1
1
Logical expression:
y  AB
Output
y  AB
1
0
0
1
B
0
1
0
1
y  AB  AB
Ex-Or and Ex-Nor gates can be used as Parity checker.
Parity checking is counting the numbers of 1s in an input. If the counting is an
even number then it is called as Even Parity. If the counting is an odd number,
then it is called as Odd parity.
Even number of 1s = Even Parity = Ex-Nor gate
Odd number of 1s = Odd parity = Ex-Or gate
Both the exclusive gates are having special property for more than 2 inputs. For
example: The output of Ex-Or gate (3 inputs) is high when the number of high
input is even, the output is zero ‗0‘ and when number of high inputs is odd, the
output is one ‗1‘.
Truth table for 3 input Ex-Or gate:
Inputs
A
0
0
0
0
1
1
1
1
B
0
0
1
1
0
0
1
1
C
0
1
0
1
0
1
0
1
Output
y  A B C
0
1
1
0
1
0
0
1
The output of 3 input Ex-Nor gate is high for even number of 1s and low for odd
number of 1s.
Truth table for 3 input Ex-Nor gate:
Inputs
A
0
0
0
0
1
1
B
0
0
1
1
0
0
C
0
1
0
1
0
1
Output
y  ABC
1
0
0
1
0
1
1
1
1
1
0
1
1
0
UNIVERSAL BUILDING BLOCKS
Nand gate and Nor gate are called as Universal building block because we can
construct all other gates using Nand gates or Nor gates.
PROVE THAT NAND GATE IS A UNIVERSAL GATE
(a) Nand gate as Not gate
(b) Nand gate as And gate
(c) Nand gate as Or gate
PROVE THAT NOR GATE IS A UNIVERSAL GATE
(a) Nor gate as Not gate
(b) Nor gate as Or gate
(c) Nor gate as And gate
BOOLEAN ALGEBRA LAWS:
*Boolean Algebra /Laws:1. A+1=1
TRUTH TABLE
LHS = RHS
A+ 1 = 1
WHEN A=0;0+1 = 1=RHS
WHEN A=1; 1+1 = 1= RHS
2. A+0=A
TRUTH TABLE
LHS = RHS
A+ 0 = A
WHEN A=0;0+0 = 0 =RHS( A=0)
WHEN A=1; 1+0 = 1= RHS( A=1)
3 . A . 1=A
TRUTH TABLE
LHS = RHS
A.1 = A
WHEN A=0; 0 . 1 = 0 =RHS (A=0)
WHEN A=1; 1 . 1 = 1= RHS (A=1)
4. A . 0=0
TRUTH TABLE
LHS = RHS
A.1 = A
WHEN A=0; 0 . 0 = 0 =RHS
WHEN A= 1; 1 . 0 = 0= RHS
5. A + A =A
6. A . A=A
TRUTH TABLE
LHS = RHS
A +A = A
WHEN A=0; 0 + 0 = 0 =RHS (A=0)
WHEN A=1; 1 + 1 = 1= RHS (A=1)
TRUTH TABLE
LHS = RHS
A.A = A
WHEN A=0; 0 . 0 = 0 =RHS (A=0)
WHEN A=1; 1 . 1 = 1= RHS (A=1)
7. 𝐴 = A
TRUTH TABLE
LHS = RHS
WHEN A=0; 0 =1 & 1 = 0 RHS (A=0)
WHEN A=1; 1 =0 & 0 = 1 RHS (A=1)
8. A + 𝐴= 1
TRUTH TABLE
LHS = RHS
WHEN A=0; THAN 𝐴= 1
0+1 =1 = RHS
WHEN A=1; THAN 𝐴 = 0
1+ 0 =1=RHS
9. A. 𝐴 = 0
LHS = RHS
A. 𝐴 = 0
WHEN A=0 THAN 𝐴 = 1
0.1 =0 =RHS
WHEN A=1 THAN 𝐴 = 0
1.0 =0 =RHS
 Boolean Laws
1. A+ 𝐴𝐵 = 𝐴 + 𝐵
Truth Table
Input
A
B
0
0
1
1
0
1
0
1
𝐴
1
1
0
0
LHS
A+ 𝐴𝐵
0
1
1
1
Out puts
RHS
A+B
0
1
1
1
2. A+𝐴 𝐵 = 𝐴 + 𝐵
Truth Table
Input
A
0
0
1
1
B
0
1
0
1
𝐵
𝐴
1
1
0
0
1
0
1
0
Out puts
LHS
RHS
A+ 𝐴𝐵
A+𝐵
1
1
0
0
1
1
1
1
3. 𝐴 + 𝐴𝐵 = 𝐴 + 𝐵
Truth Table
Input
A
B
𝐴
𝐵
0
0
1
1
0
1
0
1
1
1
0
0
1
0
1
0
Out puts
LHS
RHS
A+ 𝐴𝐵
A+B
1
1
1
1
0
0
1
1
4. 𝐴 + 𝐴𝐵 = 𝐴 + 𝐵
Truth Table
Input
A
B
𝐴
𝐵
0
0
1
1
0
1
0
1
1
1
0
0
1
0
1
0
Out puts
LHS
RHS
A+ 𝐴𝐵
𝐴+𝐵
1
1
1
1
1
1
0
0
Cummulitive Law
(1) A+B = B+A
(2) A.B = B.A
Truth table
Inputs
A
0
0
1
1
Outputs - I
B
0
1
0
1
Distributive Law
(1) A(B+C) = AB+AC
(2) A+(B.C)=(A+B)(A+C)
Truth table
Inputs
A
B
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
A+B
0
1
1
1
C
0
1
0
1
0
1
0
1
Output II
B+A
0
1
1
1
Outputs - I
A(B+C)
AB+AC
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
A.B
0
0
0
1
B.A
0
0
0
1
Output II
A+(BC)
(A+B)(A+C)
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
Associative Law
(1) A+(B+C) = (A+B)+C= A+B+C
(2) A(B.C)=(AB)C=A.B.C
Truth Table
Inputs
Outputs - I
Output II
A
B
C
A(B+C) (A+B)+C A+B+C A(BC) (AB)C ABC
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
1
0
1
1
1
0
0
0
0
1
1
1
1
1
0
0
0
1
0
0
1
1
1
0
0
0
1
0
1
1
1
1
0
0
0
1
1
0
1
1
1
0
0
0
1
1
1
1
1
1
1
1
1
Demorgan‘s Theorem
First Theorem:- Demorgan‘s first theorem gives the equivalence between NOR gate and AND
gate we can replace ‗+‘by ‗.‘
This theorem states that ―The complement of sum is equal to the product of complements‖
𝐴 + 𝐵 = 𝐴. 𝐵
The NOR gate is equivalent to bubbled AND gate
Truth Table
Inputs
Outputs
𝐵
𝐴
A
B
LHS
RHS
𝐴+𝐵
𝐴. 𝐵
0
0
1
1
1
1
0
1
1
0
0
0
1
0
0
1
0
0
1
1
0
0
0
0
Second theorem:This theorem gives the equivalence between NAND gate and OR gate. We can replace ‗.‘ with
‗+‘
It states that the complement of product is equal to the sum of the complement.
The NAND gate is equivalent to bubbled OR gate.
Truth Table
Inputs
A
B
𝐴
𝐵
0
0
1
1
0
1
0
1
1
1
0
0
1
0
1
0
Outputs
LHS
RHS
𝐴∙𝐵
𝐴+𝐵
1
1
1
1
1
1
0
0
 Demorgan‘s Theorem for 3 variables:First Theorem:𝐴+𝐵+𝐶 = 𝐴∙ 𝐵∙𝐶
Truth Table
Input
Out puts
LHS
RHS
𝐶
A
B
𝐴+𝐵+𝐶
𝐴∙ 𝐵∙𝐶
0
0
0
1
1
0
0
1
0
0
0
1
0
0
0
0
1
1
0
0
1
0
0
0
0
1
0
1
0
0
1
1
0
0
0
1
1
1
0
0
Second Theorem:𝐴. 𝐵. 𝐶. = 𝐴 + 𝐵 + 𝐶
TRUTH TABLE
Input
A
B
𝐶
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Out puts
LHS
RHS
𝐴. 𝐵. 𝐶.
𝐴+𝐵+𝐶
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
Half Adder:Description:- It can add two bits i.e. two binary bits & the addition of two binary
bits will have two outputs i.e. sum & carry. The circuit can be designed using
truth table. Below shows the block diagram and the truth table of Half adder.
Block Diagram
Truth Table:A
0
0
1
1
B
0
1
0
1
SUM
0
1
1
0
CARRY
0
0
0
1
Working:- The above truth table shows the addition of two bits i.e. A+B. so 4
combinations i.e. (2²= 4) & Two possible outputs Sum and carry. The sum output
is high when any one of the input is high & when both the inputs A&B are high
i.e. ‗1‘ the sum output is ‗0‘ & Carry output is high ‗1‘.
Logical Expression: - From the truth table we can derive sum & carry equations
as follows.
Sum = AB
& Carry = AB
Realization / Logical Diagram:-
Full Adder
Half adder is designed for the addition of two binary bits namely A & B but the
drawback of half adder is in multibit addition. So to overcome this drawback we
design full adder which will add 3 binary bits i.e. A+B+C & WILL HAVE TWO
OUTPUTS i.e. Sum and carry. Below shows the block diagram of full adder which
has 3 inputs A, B & C and there are two carry signals Cin & Cout. & a single
output.
Full adder can be designed with the help of truth table.
A
0
0
0
0
1
1
1
1
B
0
0
1
1
0
0
1
1
C
0
1
0
1
0
1
0
1
SUM
0
1
1
0
1
0
0
1
CARRY
0
0
0
1
0
1
1
1
SUM  A  B  C
Sum output is high or ‗1‘ when there are odd no of parity at the input side &
hence the equation for sum can also be derived as A B C
CARRY  AB  BC  AC
LOGICAL DIAGRAM
Multiplexer:Multiplexer or Data selector is a combinational circuit. It has multiple output &
one output i.e. it accepts several data inputs & allows only one of them at a
time to get through the output. Below figure shows the basic block diagram of
N: 1 Multiplexer.
The selection of data lines are dependent on the combination of select lines &
the relation between select line and data line is 2 M  N
Fig shows ‗n‘ no of input data lines. ‗m‘ no of input select lines & a single output
‗Y‘. Enable (E) pin is used to enable or disable the multiplexer
E = I/O = Enable / Disable
2:1 multiplexer:-
Fig shows the block diagram of 2:1 MUX. 2 input data lines D0, D1. One select
lines ‗S0‖. One output ‗Y‘. the 2:1 MUX can be designed with the help of truth
table.
Truth Table:-
Logical Diagram
Input
E
0
1
1
S0
X
0
1
Output
Y
0
D0
D1
When select input S0 is ‗0‘ the input data line D0 will be appearing at the output
& when S0 is ‗1‘ input data line ‗D1‖ will be appearing at the output.
4:1 Multiplexer: -
Fig shows the block diagram of 4:1 MUX. It has 4 input data lines D0, D1, D2, D3,
two select lines S0 & S1. One output ‗Y‘. the 4:1 MUX can be designed with thew
help of truth table.
E
0
1
1
1
1
Input
S0
X
0
0
1
1
S1
X
0
1
0
1
Output
Y
0
D0
D1
D2
D3
When select lines S0 = 0 & S1 = 0 then D0 will be appearing at the output. When
select lines S0 = 1 & S1 = 0 then D1 will be appearing at the output. When select
lines S0 = 0 & S1 = 1 then D2 will be appearing at the output. When Select lines
S0=1 & S1 = 1 then D3 will appear at the output.
De-multiplexer:-
De-multiplexer is exactly reverse that of multiplexer i.e. it accepts single input &
distributes among several outputs. The single input should appear over which
output line is decided by select lines. Above fog shows the generalizes block
diagram of 1: N De-multiplexer. It has one input and ‗n‘ no of output lines & ‗m‘
no of select input lines. It is having the same relation i.e.
m = no. of input select lines
n= no of output lines
1: 2 Demultiplexer
Fig shows the block diagram of 1:2 Demultiplexer. It has one input data line ‗Din‘
& 2 output lines i.e. ‗Y 0‘ & ‗Y 1‘. The select line is selected according to the
combination of select line ‗S0‘. It can be designed with the help of Truth Table.
Input
E
0
1
1
S0
X
0
1
Output
Y
0
Y0 = Din
Y1=Din
Enable pin is used to Enable / Disable the Demultiplexer. Enable / Disable = 1 / 0
When select line S0 = 0 input data line ‗Din‘ will appear at the output ‗Y0‘ line &
when select line S0 = 1 input data line ‗Din‘ will appear at the output ‗Y1‘ line.
1: 4 Demultiplexer:-
Fig shows the block diagram of 1:4 demultiplexer it has one input data line ‗Din‘
& 4 output data lines ‗Y0 – Y3‘ & 2 select lines ‗ S0& S1‘. The data line ‗Din‘ will
appear at the output as per the combination of select lines ‗S0 & S1‘. It canb be
designed with the help of truth table.
E
0
1
1
1
1
Input
S0
X
0
0
1
1
S1
X
0
1
0
1
Output
Y
0
Y0=Din
Y1=Din
Y2=Din
Y3=Din
When S0 = 0 & S1 = 0 the input Din will appear at the output line Y 0. When S0 = 0 &
S1 = 1, the input Din will appear at the output line Y1. When S0 = 1 & S1 = 0 the
input Din will appear at the output line Y2. When S0 = 1 & S1 = 1 the input Din will
appear at the output line Y3.
Difference Between Multiplexer & De-multiplexer
Multiplexer
1. It is known as MUX.
2. Multiplexing means many
into one.
3. Logic Symbol
Demultiplexer
1. It is known as DeMUX.
2. Demultiplexing means one
into many
3. Logic Symbol
4. It cannot be used as
decoder.
5. It requires OR gate at the
output.
4. It can be used as decoder.
5. It does not require OR gate at
the output.
Encoders:An encoder is a device that converts information from one code to another. For
eg.: A digital circuit like a calculator is having input numbers from 0 to 9.
Internally it uses an encoder circuit to covert decimal number to its binary
equivalent.
In computers it uses keyboard it is accepting ASCII codes its encoder is
converting input data into ASCII or BCD to process the computer data.
BCD Encoder:An encoder is a combinational circuit that converts a standard input into a
coded signal. The BCD encoder thus converts a decimal no 0 – 9 into its BCD
code (Binary coded decimal) It can be designed with the help of truth table.
It can be used with the help of switches. It uses ten switches representing
numbers 0 to 9.
Truth Table :Input
Decimal Number
0
1
2
3
4
5
6
7
8
9
Output
A
0
0
0
0
0
0
0
0
1
1
B
0
0
0
0
1
1
1
1
0
0
C
0
0
1
1
0
0
1
1
0
0
D
0
1
0
1
0
1
0
1
0
1
When a particular decimal number is pressed by operating its switch it connects
+5V to the corresponding OR gate it generates its equivalent BCD code. When
decimal 8 is pressed only A is high input & therefore the output of encoder is
ABCD = 1000. When 5 is pressed only B & D is high & therefore the output of
encoder is ABCD = 0101 & so on.
Decoders:It is a combinational logic circuit that converts encoded signal back to its
original form. For eg:- BCD encoder converts decimal number into its BCD code.
& the decoder circuit converts this BCD code to its decimal equivalent.
BCD TO 7 Segment Display:To study BCD TO 7 Segment display we need to understand the concept of 7
segment display. It consist of an arrangement of LED‘s in a 8 form. Below shows
the diagram of the same.
The above display will consist of 7 LED‘s & generate decimal numbers 0 - 9
according to the truth table. The LED‘s ‗a-g‘ will glow according to the decimal
no to be generated for eg:- when BCD input is 1000 i.e decimal 8 all the LED‘s
will glow and display decimal no 8. When BCD input is 1001 i.e. decimal 9 only
‗c‘ & ‗d‘ LED‘s will be turned off rest all LED‘s will glow.
Truth Table:A
0
0
0
0
0
0
0
0
1
1
B
0
0
0
0
1
1
1
1
0
0
C
0
0
1
1
0
0
1
1
0
0
D
0
1
0
1
0
1
0
1
0
1
a
1
0
1
1
0
1
0
1
1
1
b
1
1
1
1
1
0
0
1
1
1
c
1
1
0
1
1
1
1
1
1
1
d
1
0
1
1
0
1
1
0
1
0
e
1
0
1
0
0
0
1
0
1
0
f
1
0
0
0
1
1
1
0
1
1
G
0
0
1
1
1
1
1
0
1
1
3. FUNCTIONAL HARDWARE OF PC
CONCEPT OF HARDWARE AND SOFTWARESOFTWARE- Software is set of instructions or data that can be store electronically.
There are two types of softwares-1) System software (operating systems)
2) Application software (programs)
HARDWARE- Hardware is the storage device and display device.
PC SPECIFICATIONMOTHERBOARD-
A motherboard is physical arrangement in computer that contains the
computer‘s basic circuitry and components.
The computer components include in the motherboard are1) Microprocessor- The microprocessor, also known as the Central Processing
Unit (CPU)is the brain of all computers and many household and electronics
devices.
2) coprocessor- A coprocessor is a computer processor used to supplement the
functions of the primary processor (the CPU).
3) Basic input/output system- BIOS (basic input/output system) is the program a
personal computer's microprocessor uses to get the computer system started
after you turn it on. It also manages data flow between the computer's
operating system and attached devices such as the hard disk, video adapter,
keyboard, mouse and printer.
4) Expansion slot- An opening in a computer where a circuit board can be
inserted to add new capabilities to the computer.
5) Interconnecting circuitry- A flexible printed circuit interconnecting cable
which includes a flexible circuitry assembly including an array of conductors
mounted on a flexible substrate film and covered with a flexible covering film.
CPU PROPERTIES1) CLOCK FREQUENCY- It specifies the execution speed of CPU it is operated
with clock.
2) BUS WIDTH- It specifies the word size in number of lines available for carrying
data at a time.
3) SERIAL PORT- It specifies whether serial communication is provided or not,
because peripheral may require serial data transfer.
TYPES OF MEMORIES1) CONVENTIONAL MEMORY- Conventional memory, also called base memory,
is the first 640 kilobytes (640 × 1024 bytes) of the memory on IBM PC or
compatible systems. It is the read-write memory directly addressable by the
processor for use by the operating system and application programs. As
memory prices rapidly declined, this design decision became a limitation in the
use of large memory capacities until the introduction of operating systems and
processors that made it irrelevant.
2)EXPANDED MEMORY- In DOS memory management, expanded memory is a
system of bank switching that provided additional memory to DOS programs
beyond the limit of conventional memory (640 KB).
3) EXTENDED MEMORY- Computer system having an extended memory which permits
the running of a plurality of operating systems (OS) on one computer having main
memory and at least one extended memory and which includes at least one virtual
main memory which permits each of the plurality of OSs to reside on main memory, at
least one virtual extended memory (virtual ES) residing on the extended memory.
4) PHYSICAL
AND LOGICAL MEMORY- Physical refers to anything related to
hardware. The opposite of physical
is logical or virtual, which describes
softwares.eg. physical memory refers to the RAM CHIPS installed in computer and
virtual memory is an imaginary area used by programs.
SEMICONDUCTOR MEMORIES1) ROM- Random-access memory (RAM) is a form of computer data storage. A
random-access memory device allows data items to be accessed (read or
written) in almost the same amount of time irrespective of the physical location of
data inside the memory. In contrast, with other direct-access data storage media
such as hard disks, CD-RWs, DVD-RWs and the older drum memory, the time
required to read and write data items varies significantly depending on their
physical locations on the recording medium, due to mechanical limitations such
as media rotation speeds and arm movement delays.
2)ROM- Read-only memory (ROM) is a class of storage medium used in computers
and other electronic devices. Data stored in ROM can only be modified slowly, with
difficulty, or not at all, so it is mainly used to distribute firmware (software that is very
closely tied to specific hardware and unlikely to need frequent updates).
Strictly, read-only memory refers to memory that is hard-wired, such as diode
matrix and the later mask ROM. Although discrete circuits can be altered (in
principle), integrated circuits (ICs) cannot and are useless if the data is bad. The
fact that such memory can never be changed is a large drawback; more
recently, ROM commonly refers to memory that is read-only in normal operation,
while reserving the fact of some possible way to change it.
3)PROM-A programmable read-only memory (PROM) or field programmable
read-only memory (FPROM) or one-time programmable non-volatile memory
(OTP NVM) is a form of digital memory where the setting of each bit is locked by
a fuse or antifuse. They are a type of ROM (read-only memory) meaning the
data in them is permanent and cannot be changed. PROMs are used in digital
electronic devices to store permanent data, usually low level programs such as
firmware (microcode). The key difference from a standard ROM is that the data
is written into a ROM during manufacture, while with a PROM the data is
programmed into them after manufacture. Thus, ROMs tend to be used only for
large production runs with well-verified data, while PROMs are used to allow
companies to test on a subset of the devices in an order before burning data
into all of them.
4)EPROM
-EPROM
(erasable
programmable
read-only
memory)
is
programmable read-only memory (programmable ROM) that can be erased
and re-used. Erasure is caused by shining an intense ultraviolet light through a
window that is designed into the memory chip.
TYPES OF SYSYTEM BUSES- A bus is simply a channel over which information flows
between two or more devices.
1) DATA BUS-Data bus are the lines that actually carry the data being transferred
.it is bidirectional bus.
2) ADRESS BUS- Address bus is the set of lines that carry information about where
in memory the data is to be transferred. It is unidirectional bus.
3) CONTROL BUS-Control bus is used to send different control signals like read,
write signals to the memory , some control signals sent on this control bus used to
identify the type of device, processor wants to interact with.
4) UNIVERSAL SERIAL BUS- A two way, high speed serial interface to which you
can dynamically connect and disconnect .USB has been around for few years
and USB port are fitted to just about every computer now.
4.Peripheral devices
Introduction-Computer system mainly designed to accept input data through
input device process it and display or print the results.
INPUT DEVICESTHERE ARE FOLLOWING TYPES OF INPUT DEVICES:
1) KEYBOARDIn computing, a computer keyboard is a typewriter-style device which uses an
arrangement of buttons or keys to act as mechanical levers or electronic
switches. Following the decline of punch cards and paper tape, interaction via
teleprinter-style keyboards became the main input device for computers.
1) Keyboard allows all alphanumeric set 0-9, A to Z in small and capital.
2) Keyboard available in two types-
1) 84 keys
2) 101 enhanced keys
2) MOUSEA computer mouse is a pointing device (hand control) that detects twodimensional motion relative to a surface. This motion is typically translated into
the motion of a pointer on a display, which allows for fine control of a graphical
user interface.
Physically, a mouse consists of an object held in one's hand, with one or more
buttons. Mice often also feature other elements, such as touch surfaces and
"wheels", which enable additional control and dimensional input.
ACTIONS RELATED TO MOUSE1) Single click
2) Double click
3) To move
4) Dragging
3) SCANNERIn computing, an image scanner—often abbreviated to just scanner, although
the term is ambiguous out of context (barcode scanner, CAT scanner, etc.)—is a
device that optically scans images, printed text, handwriting, or an object, and
converts it to a digital image. Commonly used in offices are variations of the
desktop flatbed scanner where the document is placed on a glass window for
scanning. Hand-held scanners, where the device is moved by hand, have
evolved from text scanning "wands" to 3D scanners used for industrial design,
reverse engineering, test and measurement, orthotics, gaming and other
applications. Mechanically driven scanners that move the document are
typically used for large-format documents, where a flatbed design would be
impractical.
OUTPUT DEVICES1) VIDEO(MONITOR)A computer monitor or a computer display is an electronic visual
display for computers. A monitor usually comprises the display device, circuitry,
casing, and power supply. The display device in modern monitors is typically
a thin film transistor liquid crystal display (TFT-LCD) or a flat panel LED display,
while older monitors used a cathode ray tubes (CRT). It can be connected to
the computer via VGA, DVI, HDMI, Display Port, Thunderbolt, LVDS (Low-voltage
differential signaling) or other proprietary connectors and signals.
Originally, computer monitors were used for data processing while television
receivers were used for entertainment. From the 1980s onwards, computers (and
their monitors) have been used for both data processing and entertainment,
while televisions have implemented some computer functionality. The
common aspect ratio of televisions, and computer monitors,
VIDEO MONITOR/BOARD CHARACTERISTICS1)RESOLUTION- In computers, resolution is the number of pixels (individual points
of color) contained on a display monitor, expressed in terms of the number of
pixels on the horizontal axis and the number on the vertical axis. The sharpness of
the image on a display depends on the resolution and the size of the monitor.
2) DOT PITCH- Dot pitch, or "pixel pitch," is a measurement that defines the
sharpness of a display. It measures the distance between the dots used to
display the image on the screen. This distance is very small and is typically
measured in fractions of millimeters. The smaller the dot pitch, the sharper the
picture.
3) HORIZONTAL SCAN FREQUENCY-The number of lines illuminated on a video
screen in one second. For example, a resolution of 400 lines refreshed 60 times
per second requires a scan rate of 24 kHz (60 x 400) plus time to bring the beam
back to the beginning of the next line.
4) MULTI-SYNC-The ability of monitor to handle multiple resolution automatically
is called multyncing.
2)PRINTERS-1) IMPACT PRINTER - 1) DOT-MATRIX PRINTER
2) NON-IMPACT PRINTER- 1 ) LASER PRINTER
2) INK-JET PRINTER
DOT MATRIX PRINTER-Dot matrix printing or impact matrix printing is a type
of computer printing which uses a print head that moves back-and-forth, or in
an up-and-down motion, on the page and prints by impact, striking an inksoaked cloth ribbon against the paper, much like the print mechanism on
a typewriter. However, unlike a typewriter or daisy wheel printer, letters are
drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be
produced.
Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is
driven forward by the power of a tiny electromagnet or solenoid, either directly
or through small levers (pawls). Facing the ribbon and the paper is a small guide
plate named ribbon mask holder or protector, sometimes also
called butterfly for its typical shape. It is pierced with holes to serve as guides for
the pins. This plate may be made of hard plastic.
LASER PRINTERLaser printing is an electrostatic digital printing process. It produces high-quality
text and graphics (and moderate-quality photographs) by repeatedly passing
a laser beam back and forth over a negatively charged cylindrical drum to
define a differentially-charged image. The drum then selectively collects
electrically charged powdered ink (toner), and transfers the image to paper,
which is then heated in order to permanently fuse the text and/or imagery. As
with
digital
photocopiers and
multifunction/all-in-one inkjet
printers,
laser printers employ axerographic printing process. However, laser printing
differs from analog photocopiers in that the image is produced by the direct
scanning of the medium across the printer's photoreceptor. This enables laser
printing to copy images more quickly than most photocopiers.
Invented at Xerox PARC in the 1970s, laser printers were introduced for the office
and then home markets in subsequent years by IBM, Canon, Xerox, Apple,
Hewlett-Packard and many others. Over the decades, quality and speed have
increased as price has fallen, and the once cutting-edge printing devices are
now ubiquitous.
INK-JET PRINTER- Inkjet printing is a type of computer printing that recreates
a digital image by propelling droplets of ink onto paper, plastic, or other
substrates. Inkjet printers are the most commonly used type of printer, and range
from small inexpensive consumer models to expensive professional machines.
The concept of inkjet printing originated in the 20th century, and the technology
was first extensively developed in the early 1950s. Starting in the late 1970s inkjet
printers that could reproduce digital images generated by computers were
developed, mainly by Epson, Hewlett-Packard (HP), and Canon. In the
worldwide consumer market, four manufacturers account for the majority of
inkjet printer sales: Canon, HP, Epson, and Lexmark, a 1991 spin-off from IBM.
The emerging ink jet material deposition market also uses inkjet technologies,
typically print heads using piezoelectric crystals, to deposit materials directly on
substrates.