Friday, June 29, 2012
EAMCET 2012 results
SAMSUNG Freshers Hiring 2011
SAMSUNG Freshers hiring - Samsung-2010/2011:B.E/ME/MTech/MS -70% (Hiring Freshers)
If any 2010/2011 passed-out is there who is having more than 70% , forward your resume to Employee.
Aci Icon 1100
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| Aci Icon 1100 |
- CPU: VIA CPU
- Display: 10.2" LED (1024 x 768 resolution)
- Memory: 512MB expandable to 1.0GB RAM
- Storage: 4GB expandable to 32GB
- Sound System: High Definition Audio
- I/O Port: 3 USB 2.0
- Communication: 10/100 Ethernet Adaptor, Wireless Adaptor, 3G Ready (Optional)
- Card Reader: 1 Push Card Reader, MMC / SD
- Imaging Device: Web Cam
- Dimension: 11.0(W) x 7.25 (D) 1.0 (H)
- Weight: 0.7Kg with Battery
ACi ICON 1100 online booking now available in www.aci-asia.com
Thursday, June 28, 2012
Wednesday, May 30, 2012
Fresher's Recruitment Drive - 2nd June 2012
Greetings!
We are planning to conduct a Fresher recruitment drive on 02nd June, 2012 (Saturday). If you have your friends/references who are BE/B.Tech/B.Sc/MCA 2011/2012 pass outs, e-mail their resumes to star@aspiresys.com with the subject line "ASP-TRN-D2012". Since the aptitude test is on Saturday, we are looking at candidates who are currently in Chennai and can make it to the test.
Please be informed of the following:
· This drive is for DU3 – Testing. (Manual/Automation Testing)
· TA team will review the resumes and shortlist candidates for tests.
· We will mail the admit card for the tests to the individuals and candidates without admit cards will not be allowed to take the test.
· We will have only the Test on Saturday and for the candidates shortlisted from the tests, interviews will happen on Sunday. (next day)
· Aspirians who had sent resumes earlier are requested to forward the resumes again, provided the candidates had not appeared in Aspire's interview process during the last 6 months. (This is primarily to ensure that the candidates are still looking out for an opportunity and we are calling only the available candidates)
· We are planning to meet about 250 candidates on Saturday.
It is not a walk in and only candidates with admit cards will be allowed to take the test. Refer a Junior Star as bright as you!
Have an exciting day ahead!!
Supreme Court IT posts May - 2012
Hi All,
SUPREME COURT OF INDIA
Applications in the prescribed form are invited from Indian citizens who fulfill the essential qualifications and other eligibility conditions for following posts :
- Branch Officer (System Administrator) : Pay Scale : Rs.1560-39100 grade pay Rs.6600
- Court Assistant (Technical Assistant-cum-Programmer) : Pay Scale : Rs.9300-34800 grade pay Rs.4200
"Branch Officer (System Administrator)" and "Court Assistant (Technical Assistant-cum-Programmer)" thereon and addressed to Registrar (Admn.I), Supreme Court of India, Tilak Marg, New Delhi-110001 may be sent so as to reach him on or before 25/06/2012
For more information and application format, kindly view http://supremecourtofindia.nic.in/outtoday/techadv11052012.pdf
Friday, May 25, 2012
Thursday, May 24, 2012
Tuesday, May 22, 2012
HCL OFF Campus for 2011 & 2012 pass outs.
Monday, May 21, 2012
AP SSC 2012 Results on 24 May at 11.00 AM
www.manabadi.com
www.schools9.com
www.mypulsrate.com
www.manachaduvu.com
Friday, May 11, 2012
C FAQ
A) switch statement is generally best to use when you have more than two
conditional expressions based on a single variable of numeric type.
2 What is the difference between goto and longjmp() and setjmp()?
A) goto statement implements a local jump of program execution, and the
longjmp() and setjmp() functions implement a nonlocal, or far, jump of
program
execution. General...
3 What is an lvalue?
A) An lvalue is an expression to which a value can be assigned. The lvalue
expression is located on the left side of an assignment statement,
whereas an
rvalue is located on the ...
4 Array is an lvalue or not?
A) An lvalue was defined as an expression to which a value can be
assigned. Is
an array an expression to which we can assign a value? The answer to this
question is no, because an array...
5 What is page thrashing?
A) Some operating systems (such as UNIX or Windows in enhanced mode)
use virtual
memory. Virtual memory is a technique for making a machine behave as
if it had
more memory ...
6 What is a const pointer?
A)The access modifier keyword const is a promise the programmer makes
to the
compiler that the value of a variable will not be changed after it is
initialized. The compiler will enforc...
7 When should the register modifier be used? Does it really help?
A) The register modifier hints to the compiler that the variable will be
heavily used and should be kept in the CPU's registers, if possible,
so that it
can be accessed faster. There ar...
8 when should the volatile modifier be used?
A) The volatile modifier is a directive to the compiler's optimizer that
operations involving this variable should not be optimized in certain
ways.
There are two special cases in which...
9 Can a variable be both const and volatile?
A) Yes. The const modifier means that this code cannot change the
value of the
variable, but that does not mean that the value cannot be changed by means
outside this code. For instance...
10 How reliable are floating-point comparisons?
A) Floating-point numbers are the "black art" of computer programming. One
reason why this is so is that there is no optimal way to represent an
arbitrary
number. The Institute of Elect...
11 How can you determine the maximum value that a numeric variable can
hold?
A) For integral types, on a machine that uses two's complement arithmetic
(which is just about any machine you're likely to use), a signed type
can hold
numbers from –2(number of bits –...
12 When should a type cast be used?
A) There are two situations in which to use a type cast. The first use
is to
change the type of an operand to an arithmetic operation so that the
operation
will be performed properly.&n...
13 When should a type cast not be used?
A) A type cast should not be used to override a const or volatile
declaration.
Overriding these type modifiers can cause the program to fail to run
correctly.
14 Is it acceptable to declare/define a variable in a C header?
A) global variable that must be accessed from more than one file can
and should
be declared in a header file. In addition, such a variable must be
defined in
one source file. Variable...
15 What is the difference between declaring a variable and defining a
variable?
A) Declaring a variable means describing its type to the compiler but not
allocating any space for it. Defining a variable means declaring it
and also
allocating space to hold the variable
16 Can static variables be declared in a header file?
A) You can't declare a static variable without defining it as well
(this is
because the storage class modifiers
static and extern are mutually exclusive). A static variable...
17 What is the benefit of using const for declaring constants?
The benefit of using the const keyword is that the compiler might be
able to
make optimizations based on the knowledge that the value of the
variable will
not change. In addition, th...
18 What is the easiest sorting method to use?
The answer is the standard library function qsort(). It's the easiest
sort by
far for several reasons:
It is already written.
It is already debugged.
...
19 What is the quickest sorting method to use?
The answer depends on what you mean by quickest. For most sorting
problems, it
just doesn't matter how quick the sort is because it is done
infrequently or
other operations take sign...
20 How can I sort things that are too large to bring into memory?
A sorting program that sorts items that are on secondary storage (disk or
tape) rather than primary storage (memory) is called an external sort.
Exactly
how to sort large data...
21 What is the easiest searching method to use?
Just as qsort() was the easiest sorting method, because it is part of the
standard library, bsearch() is the
easiest searching method to use. If the given array is in th...
22 What is the quickest searching method to use?
A binary search, such as bsearch() performs, is much faster than a linear
search. A hashing algorithm can provide even faster searching. One
particularly
interesting and fast method ...
23 What is hashing?
To hash means to grind up, and that's essentially what hashing is all
about.
The heart of a hashing algorithm is a hash function that takes your
nice, neat
data and grinds it into so...
24 How can I sort a linked list?
Both the merge sort and the radix sort are good sorting algorithms to
use for
linked lists.
25 How can I search for data in a linked list?
Unfortunately, the only way to search a linked list is with a linear
search,
because the only way a linked list's members can be accessed is
sequentially.
Sometimes it is quicker to ...
26 How do you redirect a standard stream?
Most operating systems, including DOS, provide a means to redirect program
input and output to and from different devices. This means that rather
than your
program output (stdout) go...
27 How can you restore a redirected standard stream?
The preceding example showed how you can redirect a standard stream from
within your program. But what if later in your program you wanted to
restore the
standard stream to its or...
28 What is the difference between text and binary modes?
Streams can be classified into two types: text streams and binary streams.
Text streams are interpreted, with a maximum length of 255 characters.
With text
streams, car...
29 How do you determine whether to use a stream function or a low-level
function?
Stream functions such as fread() and fwrite() are buffered and are more
efficient when reading and writing text or binary data to files. You
generally
gain better performance by usin...
30 How can I open a file so that other programs can update it at the same
time?
Your C compiler library contains a low-level file function called
sopen() that
can be used to open a file in shared mode. Beginning with DOS 3.0,
files could
be opened in shar...
31 How can I make sure that my program is the only one accessing a file?
By using the sopen() function you can open a file in shared mode and
explicitly deny reading and writing permissions to any other program
but yours.
This task is accomplished by usin...
32 What is Preprocessor?
The preprocessor is used to modify your program according to the
preprocessor
directives in your source code. Preprocessor directives (such as
#define) give
the preprocessor s...
33 What is a macro, and how do you use it?
A macro is a preprocessor directive that provides a mechanism for token
replacement in your source code. Macros are created by using the #define
statement.
Here is...
34 What will the preprocessor do for a program?
The C preprocessor is used to modify your program according to the
preprocessor directives in your source code. A preprocessor directive is a
statement (such as #define) that ...
35 How can you avoid including a header more than once?
One easy technique to avoid multiple inclusions of the same header is
to use
the #ifndef and #define
preprocessor directives. When you create a header for your program, ...
36 Can a file other than a .h file be included with #include?
The preprocessor will include whatever file you specify in your #include
statement. Therefore, if you have the line
#include <macros.inc>
in you...
37 What is the benefit of using #define to declare a constant?
Using the #define method of declaring a constant enables you to declare a
constant in one place and use it throughout your program. This helps
make your
programs more maintainable, b...
38 What is the benefit of using an enum rather than a #define constant?
The use of an enumeration constant (enum) has many advantages over
using the
traditional symbolic constant
style of #define. These advantages include a low...
39 How are portions of a program disabled in demo versions?
If you are distributing a demo version of your program, the
preprocessor can
be used to enable or disable
portions of your program. The following portion of code shows h...
40 Is it better to use a macro or a function?
The answer depends on the situation you are writing code for. Macros
have the
distinct advantage of being more efficient (and faster) than
functions, because
their corresponding code...
41 What is the difference between #include <file> and #include "file"?
When writing your C program, you can include files in two ways. The
first way
is to surround the file you
want to include with the angled brackets < and >. This me...
42 Can you define which header file to include at compile time?
Yes. This can be done by using the #if, #else, and
Thursday, May 10, 2012
BEL recruitment
MBA/PGDM
MSW
PG Diploma
Location: Delhi
Job Category: Core Technical, Govt Sector, MBA
Last Date: 10 May 12
Hiring Process: Written-test.
| Post Name | Qualification | No. of Post |
Probationary Engineer (PE)
| Candidates with first class in B.E / B.Tech / B.Sc Engineering Graduate from AICTE approved Colleges in Electronics / Electronics and Communication / Electronics & Telecommunication / Communication / Telecommunication / Mechanical / Computer Science / Computer Science and Engineering. Candidates with first class in AMIE / GIETE, in the above disciplines are also eligible to apply. SC/ST/PWDcandidates with pass in the above degree / disciplines are eligible to apply. |
177 (Electronics – 88, Mechanical – 32, Computer Science – 50, Human Resource – 07)
|
| Probationary Officer (HR) | Candidates - Graduation with First class in MSW/MBA (2 years fulltime with specialization in HRM/Personnel Management and Industrial Relations) / First class in Postgraduate Degree / Postgraduate Diploma (2 years fulltime) in HRM / Personnel Management & Industrial Relations from a recognised University / Institute. For SC/ST/PWD candidates – Graduation and pass in any of the above Postgraduate qualifications. |
| Date of submission of Online Application | 25 April 2012 to 10 May 2012 |
| Last Date of Receipt of Filled Form along with Bank Challans (wherever required) | 16 May 2012 |
| Date for downloading admit cards from BEL Website | 8 June 2012 at 1400 hours (tentative) |
| Date of Written Examination | 01 July 2012 (Sunday) |
Wednesday, May 9, 2012
Engineering Graduates (B.E./B.Tech/B.Sc (Engg) as Management Trainee
Engineering Graduates (B.E./B.Tech/B.Sc (Engg) as Management Trainee
Management Trainee: Mechanical, Chemical, Civil, Electrical, Information Technology/Computer Science
Eligibility Criteria
HOW TO APPLY
Important Dates
Sunday, May 6, 2012
TV show Satyamev Jayate 1
In this episode Aamir talks about the killing of unborn girls, or female foeticide, an alarming and frightening reality. It involves the collusion of families, doctors and a social structure that encourages the desire for a boy child - at any cost. The result has been the death of over 3 crore unborn girls since independence and a generation of young men, many amongst whom will find it very tough to get a life partner.
Friday, April 27, 2012
BHARAT ELECTRONICS LIMITED (BEL)
BHARAT ELECTRONICS LIMITED (BEL)
(A Govt. of India Enterprise)
Recruitment of Probationary Engineers
Bharat Electronics Limited (BEL), a Navratana company and India's premier professional electronics company requires Graduate Engineers as Probationary Engineers :
- Probationary Engineers : 177 posts (Electronics-88, Mechanical-32, Computer Sc.-50)
- Probationary Officer : 07 posts in HR discipline
Please visit http://www.bel-india.com/index.aspx?q=§ionid=144 for more information and online submission application form from 25/04/2012 onwards.
Thursday, April 19, 2012
Worthy reading
TAKE TIME TO READ. It's worth reading it. Trust me :)
Professor: Student , Do you believe in GOD ?
Student : Absolutely, sir.
Professor : Is GOD good ?
Student : Sure.
Professor: Is GOD all powerful ?
Student : Yes.
Professor: My brother died of cancer even though he prayed to GOD to heal him. Most of us would attempt to help others who are ill. But GOD didn't. How is this GOD good then? Hmm?
(Student was silent.)
Professor: You can't answer, can you ? Let's start again, young fella. Is GOD good?
Student : Yes.
Professor: Is satan good ?
Student : No.
Professor: Where does satan come from ?
Student : From … GOD …
Professor: That's right. Tell me son, is there evil in this world?
Student : Yes.
Professor: Evil is everywhere, isn't it ? And GOD did make everything. Correct?
Student : Yes.
Professor: So who created evil ?
(Student did not answer.)
Professor: Is there sickness? Immorality? Hatred? Ugliness? All these terrible things exist in the world, don't they?
Student : Yes, sir.
Professor: So, who created them ?
(Student had no answer.)
Professor: Science says you have 5 Senses you use to identify and observe the world around you. Tell me, son, have you ever seen GOD?
Student : No, sir.
Professor: Tell us if you have ever heard your GOD?
Student : No , sir.
Professor: Have you ever felt your GOD, tasted your GOD, smelt your GOD? Have you ever had any sensory perception of GOD for that matter?
Student : No, sir. I'm afraid I haven't.
Professor: Yet you still believe in Him?
Student : Yes.
Professor : According to Empirical, Testable, Demonstrable Protocol, Science says your GOD doesn't exist. What do you say to that, son?
Student : Nothing. I only have my faith.
Professor: Yes, faith. And that is the problem Science has.
Student : Professor, is there such a thing as heat?
Professor: Yes.
Student : And is there such a thing as cold?
Professor: Yes.
Student : No, sir. There isn't.
(The lecture theater became very quiet with this turn of events.)
Student : Sir, you can have lots of heat, even more heat, superheat, mega heat, white heat, a little heat or no heat. But we don't have anything called cold. We can hit 458 degrees below zero which is no heat, but we can't go any further after that. There is no such thing as cold. Cold is only a word we use to describe the absence of heat. We cannot measure cold. Heat is energy. Cold is not the opposite of heat, sir, just the absence of it.
(There was pin-drop silence in the lecture theater.)
Student : What about darkness, Professor? Is there such a thing as darkness?
Professor: Yes. What is night if there isn't darkness?
Student : You're wrong again, sir. Darkness is the absence of something. You can have low light, normal light, bright light, flashing light. But if you have no light constantly, you have nothing and its called darkness, isn't it? In reality, darkness isn't. If it is, well you would be able to make darkness darker, wouldn't you?
Professor: So what is the point you are making, young man ?
Student : Sir, my point is your philosophical premise is flawed.
Professor: Flawed ? Can you explain how?
Student : Sir, you are working on the premise of duality. You argue there is life and then there is death, a good GOD and a bad GOD. You are viewing the concept of GOD as something finite, something we can measure. Sir, Science can't even explain a thought. It uses electricity and magnetism, but has never seen, much less fully understood either one. To view death as the opposite of life is to be ignorant of the fact that death cannot exist as a substantive thing.
Death is not the opposite of life: just the absence of it. Now tell me, Professor, do you teach your students that they evolved from a monkey?
Professor: If you are referring to the natural evolutionary process, yes, of course, I do.
Student : Have you ever observed evolution with your own eyes, sir?
(The Professor shook his head with a smile, beginning to realize where the argument was going.)
Student : Since no one has ever observed the process of evolution at work and cannot even prove that this process is an on-going endeavor. Are you not teaching your opinion, sir? Are you not a scientist but a preacher?
(The class was in uproar.)
Student : Is there anyone in the class who has ever seen the Professor's brain?
(The class broke out into laughter. )
Student : Is there anyone here who has ever heard the Professor's brain, felt it, touched or smelt it? No one appears to have done so. So, according to the established Rules of Empirical, Stable, Demonstrable Protocol, Science says that you have no brain, sir. With all due respect, sir, how do we then trust your lectures, sir?
(The room was silent. The Professor stared at the student, his face unfathomable.)
Professor: I guess you'll have to take them on faith, son.
Student : That is it sir … Exactly ! The link between man & GOD is FAITH. That is all that keeps things alive and moving.
P.S.
I believe you have enjoyed the conversation. And if so, you'll probably want your friends / colleagues to enjoy the same, won't you?
Forward this to increase their knowledge … or FAITH.
By the way, that student was EINSTEIN.
Transistors and Digital Logic Gates
Flow and Pressure
To begin this we will take a brief excursion into electrical engineering by way of plumbing!| Figure 1. Click to open or close the valve. See what happens to the pressure. |
The reservoir is drawn to fit the page; imagine that its capacity is very large -- on the order of that of a municipal water system. In other words, the reservoir will provide water at constant pressure and a high flow rate for a very long time.
When the valve is closed, the pressure is equal on both sides of the constriction. Click on the valve wheel to open or close the valve and observe what happens to the pressure.
When the valve is open, water escapes from the system through the open lower pipe, and the pressure in the lower pipe drops because the rate of supply is limited by the constriction. The pressure above the constriction remains high because of the reservoir supply. In other words, there is a pressure drop across the constricted pipe. The pressure drop occurs only when there is flow through the constriction; when there is no flow, the pressure is constant throughout.
Electrical Pressure
Electricity has "pressure" just as water does. Electrical pressure, or electromotive force, is measured in Volts and is often called voltage. The volume of electrical flow is measured in Amperes and is called current.A switch is an all-or-nothing device like the valve in Figure 1. There are devices that can impede the flow of electricity, similar to the constricted pipe in Figure 1. These are called resistors and they appear as a sawtooth line in a schematic diagram. The relationship among resistance, current and voltage is described by Ohm's Law,which we will not study here.
What is important to students of digital logic is this: If no current is flowing through a resistor, the voltage at the two ends will be the same; if current is made to flow through the resistor, there will be a voltage drop across the resistor. This is analogous to the pressure drop across the constricted pipe of Figure 1. The pressure drops only when water is flowing.
Consider an electric circuit that is conceptually similar to Figure 1.
| Figure 2. Click on the switch to change the state of the circuit. | |||||||
In digital logic, it is common to let a "high" voltage, that is a voltage nearly equal to Vcc indicate a logical one, and a "low" voltage -- a voltage near zero -- indicate a logical zero. In the initial state, with the switch open, both LEDs in Figure 2. are on indicating a logical value of one.
Now click on the switch to close it. Closing the switch allows current to flow from Vcc to ground. Because current is flowing, there is a voltage drop across the resistor. The voltage at the lower end, labeled "Output," becomes approximately zero as shown by the extinguished LED. The upper LED remains on because it is connected to Vcc. In future circuits, we will not bother to show the upper LED because it is on all the time.
An important thing to notice about Figure 2. is that the output is true, or one, when the switch is open. This circuit is an inverter; it computes the Boolean NOT function.
Transistors as Switches
At last we are ready to start using transistors! A transistor is an electronic device with three elements called the base, the collector, and the emitter. Transistors can function as analog devices and are used in that way in radios, amplifiers, and similar gear. By choosing suitable transistors and providing suitable inputs, they can also function as digital devices -- switches that are either on or off.Transistors have the property that if a suitable voltage is applied to the base, current can flow between the collector and the emitter. This is exactly like the mechanical switches we've been using except that we control the switching action with voltage instead of mecahnical motion. Switches made in this way can operate at electronic speeds instead of mechanical speeds. The switching speed of a typical transistor is a few nanoseconds -- a few billionths of a second. That's how computers can operate as fast as they do.
Replacing the mechanical switch with a transistor gives the circuit of Figure 3.
| Figure 3. An inverter. Click on the pushbutton to change the voltage at the base of the transistor. | |||||
The pushbutton in the diagram can be used to apply or remove voltage at the base of the transistor. Click on the pushbutton and observe what happens. When voltage is present at the base of the transistor, current flows from collector to emitter, then to ground, and there is a voltage drop across the resistor. The voltage at the output drops to near zero. Removing the voltage at the base stops the current flow and the output voltage rises to be equal to Vcc.
A transistor used in this way is an amplifier as well as a switch. A voltage lower than Vcc is enough to make the transistor switch on; very little current flows from the base to ground through the emitter. A much larger current flows from collector to emitter and then to ground. The transistor is a current amplifier, but the important part of the circuit is the voltage change at the output, from near Vcc when the transistor is switched off to near zero when the transistor is switched on.
Like the circuit in Figure 2, this circuit is an inverter. The output is high when the input is low and vice-versa. This circuit computes the Boolean NOT function.
NAND and NOR Gates
| Figure 4. A NAND gate. The value of the output is controlled by the two inputs A and B. | |||||
For purposes of this lecture we are going to define a "high" voltage -- a voltage near Vcc -- to indicate a logical 1, or true. A low voltage, near zero will indicate a logical 0, or false. (It is possible to reverse those definitions so long as one is consistent. We will not studynegative logic circuits here.)
Table 1. NAND
| A | B | X | |||
|---|---|---|---|---|---|
| 0 | 0 | 1 | |||
| 0 | 1 | 1 | |||
| 1 | 0 | 1 | |||
| 1 | 1 | 0 |
It is clear from the schematic diagram that we could build a NAND gate with more than two inputs. Adding a third transistor in series gives a three-input NAND. As an exercise, write the truth table for a three-input NAND gate. You will have inputs A, B, and C and output X.
| Figure 5. A NOR gate. The transistors are connected in parallel. | |||||||
The NAND gate has its transistors connected in series. Recall from the Electric Circuits Web Lecture that switches can be connected in series or parallel. If we connect transistors in parallel as shown in Figure 5, applying a signal to the base ofeither transistor is sufficient to allow current to flow through the resistor and pull the output voltage to near zero. This is the NOR gate. The name NOR is a contraction of not-or.
Table 2. NOR| A | B | X | |||
|---|---|---|---|---|---|
| 0 | 0 | 1 | |||
| 0 | 1 | 0 | |||
| 1 | 0 | 0 | |||
| 1 | 1 | 0 |
Let's look at the truth table for the NOR gate. Again we have inputs A and B and output X. This time, X is true, or 1, only when A and B are both 0. Another way of saying that is that X is 1 when neither A nor B is true. Experiment with the circuit to verify that it computes the function given in Table 2.
As with the NAND gate, the NOR gate can be extended to more than two inputs by adding more transistors, this time in parallel.
Figure 5 makes it obvious why the power supply voltage is called Vcc. It is connected in parallel, or in common, through the resistor to the collectors of both transistors. In a complex digital logic circuit, the same power supply voltage will be connected in common to all the gates.
About now you may be wondering why we started with NAND and NOR gates instead of the more familiar AND andOR functions. There are two reasons, one founded in electrical engineering and one founded in logic.
Although the gates shown here are simplified by comparison to the actual construction of integrated circuits, you could go to an electrical engineering lab and build the circuits of Figures 3, 4, and 5. If you did, they would function just as the animations demonstrate. These three gates, NOT, NAND, and NOR are the simplest possible digital logic gates. Each has only one transistor per input. Any other gate, and in particular the non-inverting gates AND and OR require more transistors.
Even more important is the fact that NAND and NOR are complete. This means that any other digital logic gate can be constructed using only NAND gates or only NOR gates. A manufacturer of integrated circuits can lay down a pattern of one type of gate, and then implement any digital logic function by modifying how the gates are connected.
Digital Logic Symbols
We generally don't draw individual transistors in diagramming digital logic circuits. Instead we use abstraction to suppress unnecessary detail and represent only the required information. We need to show three things about each digital logic gate: the function of the gate, the inputs, and the output. The internal construction of the gate and certain connections are suppressed.
| Figure 6. Digital Logic Symbols. A. NOT, B.NAND and C. NOR gates. |
The bullet shape is an AND gate; adding the circle makes it a NAND gate.
The shield shape is an OR gate; with a circle it becomes a NOR gate.
The inputs are shown as wires at the left of each gate, and the output is a wire on the right. Real gates require connections to Vcc and ground in addition to their inputs and outputs. These connections are not shown on digital logic symbols, but are assumed to be present. This is another example of abstraction.
The circle at the output end of each gate is called an inversion bubble. It indicates that the output is inverted. Table 1 is the truth table for a NAND gate; each bit of the output is the complement, or inverse of the corresponding bit for the AND function. Similarly, the truth table for NOR shown in Table 2 is the inverse of theOR function.
We have examined the way three types of digital logic gates are constructed.




