55. getc(),getchar(),getch(),getche().

getc()

It reads a single character from the input and return an integer value. If it fails, it returns EOF.

Here is the syntax of getc() in C

int getc(FILE *stream);

Here is an example of getc() in C language,

Example

#include
int main () {
   char val;
   printf("Enter the character: \n");
   val = getc(stdin);
   printf("Character entered: ");
   putc(val, stdout);
   return(0);
}

Output

Enter the character: a
Character entered: a

getchar()

The function getchar() reads the character from the standard input while getc() reads from the input stream. So, getchar() is equivalent to getc(stdin).

Here is the syntax of getchar() in C language,

int getchar(void);

Here is an example of getchar() in C language,

Example

#include 
int main() {
   char val;
   val = getchar();
   printf("Enter the character : \n");
   printf("Entered character : %c", val);
   return 0;
}

Output

Enter the character : n
Entered character : n

getch()

The function getch() is a non-standard function. It is declared in “conio.h” header file. Mostly it is used by Turbo C. It is not a part of C standard library. It immediately returns the entered character without even waiting for the enter key.

Here is the syntax of getch() in C language,

int getch();

Here is an example of getch() in C language,

Example

#include 
#include
int main() {
   char val;
   val = getch();
   printf("Enter the character : ");
   printf("Entered character : %c", val);
   return 0;
}

Output

Enter the character : m
Entered character : m

getche()

Like getch(), the getche() function is also a non-standard function and declared in “conio.h” header file. It reads a single character from the keyboard and returns it immediately without even waiting for enter key.

Here is the syntax of getche() in C language,

int getche(void);

Here is an example of getche() in C language,

Example

#include 
#include
int main() {
   char val;
   val = getche();
   printf("Enter the character : ");
   printf("Entered character : %c", val);
   return 0;
}

Output

Enter the character : s Entered character : s

56. Mode of file.

There are many modes in opening a file.Based on the mode of file,it can be opened for reading or writting
or appending the texts.
r – Opens a file in read mode and sets pointer to the first character in the file. It returns null if file
does not exist.
w – Opens a file in write mode. It returns null if file could not be opened. If file exists, data are
overwritten
a–Opens a file in append mode. It returns null if file couldn’t be opened.
r+ – Opens a file for read and write mode and sets pointer to the first character in the file.
w+ – Opens a file for read and write mode and sets pointer to the first character in the file.
a+ – Opens a file for read and write mode and sets pointer to the first character in the file.But,it can’t
modify existing contents.

57.File function.

a.fopen(): fopen() function is used to open a file to perform operations such as reading,writing etc.In a C
program,wr declare a file pointer and use fopin().fopen() function creates a new file if the
mentioned file name does not exist.
Syntax: FILE *fopen(const char *filename,const char *mode);
b.fclose():fclose() function closes the file that is being pointed by file pointer fp.In a C program,we close
a file.
Syntax: int fclose(FILE *fp);
c.fgets(): fgets function is used to read a file line by line.
Syntax: char *fgets(char *string,int n,FILE *fp);
d.fprint():fprint() function writes string into a file pointed by fp.
Syntax:int fprintf(FILE *fp,const char *format,…);

58. What is header file.

C language has numerous liabraries that include predefined function to make programming easier.In C
language,header files contain the set of predefined standard library functions.Your request to use a header
file in your program by including it with the C preprocessing directive “#include”.All the header file have a
‘.h’ an extension but in C,all the header files must necessarily end with the ‘.h’ extension.
A header file contains:
1.Function definitions.
2.Data type definitions.
3.Macros.
In C program should necessarily contain the header file which stands for standard input and output used to
take input with the help of scanf() and printf() function respectively.

There are of 2 types of header files:
1.Pre-existing header files:Files which are already available ic C compiler we just need to import them.
2.User-defined header

files:These files are defined by the user and can be imported using “inclued”.

Syntax:
include
include”filename.h”

59. Uses of c programming language.

C language is used to develop system applications that forms major portion of operating systems such as
windows,UNIX,Linux.Operating systems,C compiler and all UNIX application progarms are written in C language.
Below are some examples of uses of C language:
a.Database Systems.
b.Graphics packages.
c.Word processor.
d.Spread sheets.
e.Operating system development.
f.Compilers and assemblers.
g.Network drivers.
h.Interpreters.

60. Bitwise operator.

i)Bitwise operators are used to perform bit operations.Decimal values are converted into binary values
which are the sequence of bits and bitwise operators work on these bits.
ii)Bitwise operators in C language are &(bitwise AND),|(bitwise OR), ~(bitwise NOT),^(XOR),<<(left shift),
and >>(right shift).

61. ##operator

## is a pre-processor macro in C.It is used to concatenate 2 tokens into one token.
Example:
#include
#define concatenation(a,b) a ## b
int main()
{

int ab = 1000;
printf(“The concatenated value is: %d \n”);
return 0;

}

62. What is Pragma?

#pragma is a pre-processor macro in C.It is used to call a function before and after main function in a C
program.
Example:
#include

void f1(); //pragma startup f1
void f2(); //pragma exit f2

int main()
{
printf(“\n Now we are in main function”);
return 0;
}
Void f1()
{
printf(“\nFunction1 is called before main function call”);
}
Void f2()
{
printf(“\nFunction2 is called just before end of main function “);
}
Output: Function1 is called before main function call
Function2 is called just before end of main function.

63. What is a Memory leak.

The memory leak occurs,when a piece of memmory which was previously allocated by the programmer.Then it is
not deallocated properly by programmer.That memory is no longer in use by the program.So that place is reserved
for no reason.Thats why this is called the memory leak.
For the memory leak,some block of memory may have wasted.If the system has enough memory,in that case
also this may slow down the performance.

void my_func() //Here the problem is *data pointer is never deleted,so memory is wasted.
{
int *data = new int;
*data = 50;
}
#include
int main()
{ auto int my func();
my_func();
printf(“Main function\n”);
int my_func()
{
printf(“my_func function\n”);
}
printf(“done”);
return 0;
}
Output: my_func function
Main function
done

64. What is Constant pointer.

Const pointer is a pointer thst can’t change the address of the variable that is pointing to once const
pointer is made to point one variable,We can’t change this pointer to point to any other variable.This pointer
is called const pointer.
Syntax:*const;
int *const ptr;

Example:
#include
int manin()
{int a=1;
int b=2;
int *const ptr;
ptr=&a;
ptr=&b;
printf(“Value of ptr is: %d”,*ptr);
return 0;
}

65. Mathematical function in C.

“math.h” header file supports all the mathematical related functions in C language.All the arithmetic
functions used in C language are given below.
1.abs():This function returns the absolute value of an integer.The absolute value of a number is always
positive.Only integer values are supported in C.
Syntax:
Example: 

abs(-6) will return 6 and abs(6) also return 6.

2.floor():This function returns the nearest integer which is less than or equal to the arguement passed to
this function.
Syntax:double floor(double x);
Example: 

#include
int main()
{ float a=5.1,b=-6.9;
printf(“floor of %f is %f\n”,a,floor(a));
printf(“floor of %f is %f\n”,b,floor(b);
return 0;
}
Output: floor of 5.100000 is 5.000000
floor of -6.900000 is -7.000000

3.round():This function returns the nearest integer value of the float/double/long double argument passed to
this function.If decimal value is from “.1 to .5”,it returns integer value less than the argument.If decimal
value is from “.6 to .9”,it returns the integer value greater than the argument.