Computer Programming

Decimal Cases * * * () * () In programming, a floating point number is expressed as . In general, a floating-point number can be written as
where * M is the fraction mantissa or significand. * E is the exponent. * B is the base, in decimal case . Binary Cases As an example, a 32-bit word is used in MIPS computer to represent a floating-point number: 1 bit ..... 8 bits .............. 23 bits representing: * The implied base is 2 (not explicitly shown in the representation). * The exponent can be represented in signed 2's complement (but also see biased notation later). * The implied decimal point is between the exponent field E and the significand field M. * More bits in field E mean larger range of values representable. * More bits in field M mean higher precision. * Zero is represented by all bits equal to 0: Normalization To efficiently use the bits available for the significand, it is shifted to the left until all leading 0's disappear (as they make no contribution to the precision). The value can be kept unchanged by adjusting the exponent accordingly. Moreover, as the MSB of the significand is always 1, it does not need to be shown explicitly. The significand could be further shifted to the left by 1 bit to gain one more bit for precision. The first bit 1 before the decimal point is implicit. The actual value represented is
However, to avoid possible confusion, in the following the default normalization does not assume this implicit 1 unless otherwise specified. Zero is represented by all 0's and is not (and cannot be) normalized. Example: A binary number can be represented in 14-bit floating-point form in the following ways (1 sign bit, a 4-bit exponent field and a 9-bit significand field): * * * * * with an implied 1.0: By normalization, highest precision can be achieved. The bias depends on number of bits in the exponent field. If there are e bits in this field, the bias is , which lifts the representation (not the actual exponent) by half of the range to get rid of the negative parts represented by 2's complement. The range of actual exponents represented is still the same. With the biased exponent, the value represented by the notation is:

Note: * Zero exponent is represented by , the bias of the notation; * The range of exponents representable is from -126 to 127; * The exponent (with all zero significand) is reserved to represent infinities or not-a-number (NaN) which may occur when, e.g., a number is divided by zero; * The smallest exponent is reserved to represent denormalized numbers (smaller than which cannot be normalized) and zero, e.g., is represented by: Normalization: If the implied base is , the significand must be shifted multiple of q bits at a time so that the exponent can be correspondingly adjusted to keep the value unchanged. If at least one of the first q bits of the significand is 1, the representation is normalized. Obviously, the implied 1 can no longer be used. Examples: * Normalize . Note that the base is 4 (instead of 2)
Note that the significand has to be shifted to the left twobits at a time during normalization, because the smallest reduction of the exponent necessary to keep the value represented unchanged is 1, corresponding to dividing the value by 4. Similarly, if the implied base is , the significand has to be shifted 3 bits at a time. In general, if , normalization means to left shift the significand q bits at a time until there is at least one 1 in the highest q bits of the significand. Obviously the implied 1 can not be used. * Represent in biased notation with bits for exponent field. The bias is and implied base is 2.
The biased exponent is , and the notation is (without implied 1): or (with implied 1): * Find the value represented in this biased notation: The biased exponent is 17, the actual exponent is , the value is (without implied 1):
or (with implied 1):
Examples of IEEE 754: * -0.3125
The biased exponent is , * 1.0
The biased exponent is , * 37.5
The based exponent: , . * -78.25
The biased exponent: , * As the most negative exponent representable is -126, this value is a denorm which cannot be normalized: by GAURAV PANDEY & VIJAY MAHARA..........

AMRAPALI INSTITUTE...................

For all intents and purposes, there are indeed good and bad hackers when considering all the modern definitions of hackers, but the answer one would get to this question depends on whom you ask. In general, there are four categories of hackers. Each category attempts to generally convey the moral compass of that group relative to themselves and everyone else, as well as provide a basic backdrop of information on that category.

The first category of hackers are those for whom the term 'hacking' was originally defined. In this category, you have the hackers that perform the art in order to improve their knowledge of technology. They are curious about how systems work, and all of their attempts at penetration and exploits are merely expressions of this curiosity. Any damage caused is coincidental, or, if intentional, is based on revenge and not simple exploitation of innocent bystanders. Hackers were often classified by types, such as hardware hackers, computer hackers, phone hackers, etc.

In general, this category of hackers will not acknowledge the remaining three types of hackers as such. They consider the second form of hackers to be 'crackers', the third form as 'security consultants', and the fourth form as 'criminals.' This category only recognizes the classic definition of hacking, and so all hacking is good. Most everyone else, except possibly whitehats, are likely to see this category as bad due to the negative media coverage of crackers.

The second category of hackers were called crackers at large, until the media had a confusion over the various terms and simply lumped anyone that did something unusual with technology as hackers, mutating the term. Crackers are those that generally 'crack' things, such as breaking through firewalls, reverse engineering copyright protection so they can sell illegal copies, and the like; they have the same basic skills as hackers, but have a darker side to their motives.

Classic hackers generally hated the media for smearing their reputation by lumping in these malicious individuals with themselves. At some point, crackers also started using the term 'hackers' for themselves, thus further cementing the definition of hacker as 'one who does bad things with computers.' These crackers see themselves as good, or at least morally gray, and do not generally see any difference between their activities as compared to classic hackers, but are classified as bad by almost everyone else.

The third category of hackers are called whitehat hackers. Individuals in this category are a branch from the classic hackers on the 'good' side of morality. While classic hackers might say that this new group of hackers sold out on their heritage, whitehat hackers are out to make the world a better place, and line their pockets at the same time. Whitehats generally appeared after the appearance of blackhats; they seem to have appeared from the classic hacker community in response to a threat with the promise of monetary gain for their troubles.

These hackers will penetrate systems, document the flaws, and then sell this information to the organizations they have penetrated. They won't generally do so until they've been contracted by the organization to perform this work, which makes their otherwise illegal activities legal. They are essentially employed hackers for the good of humanity. Classic hackers are likely to see them as bad, having discarded their disdain for corporate greed, and blackhats see them as enemies, while the rest of the world see them as good.

The fourth category of hackers are called blackhat hackers, and represent the other side of the for-profit hacker community. They are generally crackers that have gone to the next level of the art of criminal activity. While crackers might break copyright protections for personal gain, blackhats are more interested in the big pot of gold at the end of the rainbow. Rather than sell a few lousy DVDs or cracked games, these hackers break into databases and steal millions of credit card numbers, or grab bank account numbers and transfer money out of them covertly, and other such activities.

Blackhats and whitehats are directly opposed to each other, with the good trying to defend companies against the bad. Neither group are generally interested in hackers or crackers, except possibly as recruits for their respective trades. Everyone considers this group bad, except for themselves; since most of them have little sense of morality, they usually simply exist, although some might acknowledge they are bad or have a sense of doing good by claiming that their hacker mentality against corporate greed drove them to relieve those corporations of their money. Blackhats, however, will work together for greater gains from their activities.

As one can tell, 'good' and 'bad' are relative to whom the question is asked, and even their very definitions differ even within the same group and from other groups.

!@#$%^&*() basically they are any characters that do not contain the value of a number or a letter.

All characters besides:

0123456789

abcdefghijklmnopqrstuvwxyz

ABCDEFGHIJKLMNOPQRSTUVWXYZ

and those letters with accents and diacritical marks

and those letters in other alphabet systems

Function Pointers are basically used when we want to select a function which is to be used dynamically at run time.

one of the major application of the function pointer is call back function.. i.e callback.

<><><>

A function pointer is used to pass a function as an argument to another function, or to store a function as a data item, for example a list of functions can be implemented as an array of pointers to functions. Function pointers are used to store interrupt handlers in tables.

As in most languages, a break statement is used to exit the nearest enclosing scope, including loops:

// Scilab example:

// Loop 5 times with a 50% chance of early termination on each iteration

for i=1:5

disp (i)

if rand (1,1)>0.5 then

break

end

end

// break jumps to this point