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C Programming Interview Questions and Answers Part 6

 

51. What is the sizeof () operator?

  • Even though it looks like a keyword, sizeof( ) is an operator which is used to know the memory size of the data types and variables.

  • This operator returns the number of bytes allocated for the variable (or) data type.

  • The format of the sizeof() operator is as follows.

 

sizeof (m);

where m is a variable name / data type / value.

 

52. What is a ternary operator in C?

  • Perhaps the most unusual operator in C language is one called the conditional expression operator. Unlike all other operators in C which are either unary or binary operators the conditional expression operator is a ternary operator; that is, it takes three operands.

  • The two symbols that are used to denote this operator are the question mark (?) and the colon (:). The first operand is placed before the ?, the second between the ? and the and the third after the : .

 

53.What are the advantages of auto variables?

  • The same auto variable name can be used in different blocks.

  • There is no side effect by changing the values in the blocks.

  • The memory is economically used.

  • Auto variables have inlierent protection because of local scope.

 

54.What is dynamic memory allocation?

  • A dynamic memory allocation uses functions such as malloc() or calloc() to get memory dynamically.

  • If these functions are used to get memory dynamically and the values returned by these function are assigned to pointer variables, such a way of allocating memory at run time is known as dynamic memory allocation.

 

55.What is the purpose of realloc?

  • It increases or decreases the size of dynamically allocated array.

  • The function realloc (ptr,n) uses two arguments. The first argument ptr is a pointer to a block of memory for which the size is to be altered.

  • The second argument specifies the new size.

  • The size may be increased or decreased. If sufficient space is not available to the old region the function may create a new region.

 

56.What is pointer to a pointer?

  • If a pointer variable points another pointer value. Such a situation is known as a pointer to a pointer.

  • Example :

int *p1,

**p2,

v=10;P1=&v; p2=&p1;

  • Here p2 is a pointer to a pointer.

 

57.What is the difference between linker and linkage?

  • Linker converts an object code into an executable code by linking together the necessary built in functions.

  • The form and place of declaration where the variable is declared in a program determine the linkage of variable.

 

58.What is a function?

  • A large program is subdivided into a number of smaller programs or subprograms.

  • Each subprogram specifies one or more actions to be performed for the larger program.

  • Such sub programs are called functions.

 

59.What is an argument?

  • Anargument is an entity used to pass data from the calling to a called function.

 

60.What are built in functions?

  • The functions that are predefined and supplied along with the compiler are known as built in functions.

  • They are also known as library functions.

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