how can we use static and extern?and where can we use this?
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Answer / pramod
static storage class is used for the following situations
1) the variable is defined as static within a function and
we can call the function several times, but we want that the
function should initialize the variable only once that is
during the first call to that function.So the variable will
stay alive in different calls to this function
2)In C++ , if we want a common variable between all the
objects( like a counter for how many objects have been
created) then static is allocated as it is not attached to
any object but class
extern storage is for global variables
1)if we want one varibale to be available to all the
functions in our program, make the varibale as global
variable( extern storage), it will be accessed by all the
functions in that file.But avoid declaring variable as
global for security reasons( can be accessed from any other
file in the PATH) and memory reasons (global variables are
deallocated only when the entire program terminates).
2)if we declare a variable in a file as extern , then
compiler will assume that this variable is not defined in
the present file but in some other file.So while compiling
there won't bw any error but error will come at the linking
if the extern variable is not present in the refernced files.
There is one special case
static global variable
we want a variable to be global , means accessible to all
the functions in that file and want that the variable should
not be accessible to any other file, just to make it static
global variable.So the visibility of that variable becomes
file specific only.
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the above answer is write.thanks to vignesh.
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static and extern are some types of storage classes in C...
there are four types of storage classes in C:
1) automatic (auto) storage class
2) static storage class
3) register storage class
4) extern storage class
static is a one which will be read only once by the compiler
(ie) it will ignore an another pass.... or it will be
initialized only once....... the scope of this class is
within the block only....
extern is a global declaration , but most of the compilers
dont prefer it to be used within a program.......
thank u
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Agonistic behavior, or aggression, is exhibited by most of the more than three million species of animals on this planet. Animal behaviorists still disagree on a comprehensive definition of the term, hut aggressive behavior can be loosely described as any action that harms an adversary or compels it to retreat. Aggression may serve many purposes, such as Food gathering, establishing territory, and enforcing social hierarchy. In a general Darwinian sense, however, the purpose of aggressive behavior is to increase the individual animal’s—and thus, the species’—chance of survival. Aggressive behavior may he directed at animals of other species, or it may be conspecific—that is, directed at members of an animal’s own species. One of the most common examples of conspecific aggression occurs in the establishment and maintenance of social hierarchies. In a hierarchy, social dominance is usually established according to physical superiority; the classic example is that of a pecking order among domestic fowl. The dominance hierarchy may be viewed as a means of social control that reduces the incidence of attack within a group. Once established, the hierarchy is rarely threatened by disputes because the inferior animal immediately submits when confronted by a superior. Two basic types of aggressive behavior are common to most species: attack and defensive threat. Each type involves a particular pattern of physiological and behavioral responses, which tends not to vary regardless of the stimulus that provokes it. For example, the pattern of attack behavior in cats involves a series of movements, such as stalking, biting, seizing with the forepaws and scratching with tile hind legs, that changes very little regardless of the stimulus—that is, regardless of who or what the cat is attacking. The cat’s defensive threat response offers another set of closely linked physiological and behavioral patterns. The cardiovascular system begins to pump blood at a faster rate, in preparation for sudden physical activity. The eves narrow and the ears flatten against the side of the cat’s head for protection, and other vulnerable areas of the body such as the stomach and throat are similarly contracted. Growling or hissing noises and erect fur also signal defensive threat. As with the attack response, this pattern of responses is generated with little variation regardless of the nature of the stimulus. Are these aggressive patterns of attack and defensive threat innate, genetically programmed, or are they learned? The answer seems to be a combination of both. A mouse is helpless at birth, but by its l2th day of life can assume a defensive threat position by backing up on its hind legs. By the time it is one month old, the mouse begins to exhibit the attack response. Nonetheless, copious evidence suggests that animals learn and practice aggressive behavior; one need look no further than the sight of a kitten playing with a ball of string. All the elements of attack—stalking, pouncing, biting, and shaking—are part of the game that prepares the kitten for more serious situations later in life. 7) The passage asserts that animal social hierarchies are generally stable because: a) the behavior responses of the group are known by all its members. b) the defensive threat posture quickly stops most conflicts. c) inferior animals usually defer to their physical superior. d) the need for mutual protection from other species inhibits conspecific aggression. 8) According to the author, what is the most significant physiological change undergone by a cat assuming the defensive threat position? a) An increase in cardiovascular activity b) A sudden narrowing of the eyes c) A contraction of the abdominal muscles d) The author does not say which change is most significant 9) Based on the information in the passage about agonistic behavior, it is reasonable to conclude that: I. the purpose of agonistic behavior is to help ensure the survival of the species. II. agonistic behavior is both innate and learned. III. conspecific aggression is more frequent than i aggression. a) I only b) II only c) I and II only d) I,II and III only 10) Which of the following would be most in accord with the information presented in the passage? a) The aggressive behavior of sharks is closely inked to their need to remain in constant motion. b) fine inability of newborn mice to exhibit the attack response proves that aggressive behavior must be learned. c) Most animal species that do riot exhibit aggressive behavior are prevented from doing so by environmental factors. d) Members of a certain species of hawk use the same method to prey on both squirrels and gophers. 11) The author suggests that the question of whether agonistic behavior is genetically programmed or learned: a) still generates considerable controversy among animal behaviorists. b) was first investigated through experiments on mice. c) is outdated since most scientists now believe the genetic element to be most important. d) has been the subject of extensive clinical study. 12) Which of the following topics related to agonistic behavior is NOT explicitly addressed in the passage? a) The physiological changes that accompany attack behavior in cats b) The evolutionary purpose of aggression c) Conspecific aggression that occurs in dominance hierarchies d) The relationship between play and aggression 13) The author of this passage is primarily concerned with: a) analyzing the differences between attack behavior and defensive threat behavior. b) introducing a subject currently debated among animal behaviorists. c) providing a general overview of aggressive behavior in animals. d) illustrating various manifestations of agonistic behavior among mammals.
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