Sunday, 22 March 2015

Login Program in C?

#include<conio.h>
#include<stdio.h>
#include<string.h>
void main()
{
   char userid[]="admin",password[]="123",p[15],u[15];
   int n=1,a,b;
   printf("\nEnter USER ID and PASSWORD below (You have only three chances to enter)");
   getch();
   while(n<=3)
   {
      clrscr();
      printf("\nUSER ID: ");
      scanf("%s",u);
      printf("\nPASSWORD: ");
      scanf("%s",p);
      a=strcmp(u,userid);
      b=strcmp(p,password);
      if(a==0&&b==0)
      {
         printf("\nYou have logged in successfully.");
         break;
      }
      else
      {
         printf("\nWrong PASSWORD and/or USER ID. Now you have % d more chance/s.",3-n);
      }
      getch();
      n++;
   }
   if(n==4)
      printf("\nYou can't log in.");
   getch();
}

Wednesday, 25 February 2015

Call by Value and Call by Reference

Passing Argument to Function :

In C Programming we have different ways of parameter passing schemes such as Call by Value and Call by Reference.
Function is good programming style in which we can write reusable code that can be called whenever require.
Whenever we call a function then sequence of executable statements gets executed. We can pass some of the information to the function for processing calledargument.

Two Ways of Passing Argument to Function in C Language :

Call by Reference
Call by Value

Let us discuss different ways one by one –

A.Call by Value :

#include<stdio.h>

void interchange(int number1,int number2)
{
    int temp;
    temp = number1;
    number1 = number2;
    number2 = temp;
}

int main() {

    int num1=50,num2=70;
    interchange(num1,num2);

    printf("\nNumber 1 : %d",num1);
    printf("\nNumber 2 : %d",num2);

    return(0);
}

Output :

Number 1 : 50
Number 2 : 70

Explanation : Call by Value

While Passing Parameters using call by value , xerox copy of original parameter is created and passed to the called function.
Any update made inside method will not affect the original value of variable in calling function.
In the above example num1 and num2 are the original values and xerox copy of these values is passed to the function and these values are copied into number1,number2 variable of sum function respectively.
As their scope is limited to only function so they cannot alter the values inside main function.

B.Call by Reference/Pointer/Address :

#include<stdio.h>

void interchange(int *num1,int *num2)
{
    int temp;
    temp  = *num1;
    *num1 = *num2;
    *num2 = temp;
}

int main() {

    int num1=50,num2=70;
    interchange(&num1,&num2);

    printf("\nNumber 1 : %d",num1);
    printf("\nNumber 2 : %d",num2);

    return(0);
}

Output :

Number 1 : 70
Number 2 : 50

Explanation : Call by Address

While passing parameter using call by address scheme , we are passing the actual address of the variable to the called function.
Any updates made inside the called function will modify the original copy since we are directly modifying the content of the exact memory location.

Call by Pointer or Address or Reference in C Programming Scheme

Summary of Call By Value and Call By Reference :

Point	Call by Value	Call by Reference
Copy	Duplicate Copy of Original Parameter is Passed	Actual Copy of Original Parameter is Passed
Modification	No effect on Original Parameter after modifying parameter in function	Original Parameter gets affected if value of parameter changed inside function

Wednesday, 28 January 2015

MCQ on C

What is the output of this C code?

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        int i = 0;
```
```
        int x = i++, y = ++i;
```
```
        printf("%d % d\n", x, y);
```
```
        return 0;
```
```
    }
```

a) 0, 2
b) 0, 1
c) 1, 2
d) Undefined

What is the output of this C code?

```
    #include <stdio.h>
```
```
    void main()
```
```
    {
```
```
        int x = 97;
```
```
        int y = sizeof(x++);
```
```
        printf("X is %d", x);
```
```
    }
```

a) X is 97
b) X is 98
c) X is 99
d) Run time error

What is the output of this C code?

```
    #include <stdio.h>
```
```
    void main()
```
```
    {
```
```
        int x = 4, y, z;
```
```
        y = --x;
```
```
        z = x--;
```
```
        printf("%d%d%d", x,  y, z);
```
```
    }
```

a) 3 2 3
b) 2 3 3
c) 3 2 2
d) 2 3 4

What is the output of this C code?

```
 #include <stdio.h>
```
```
    void main()
```
```
    {
```
```
        int a = 5, b = -7, c = 0, d;
```
```
        d = ++a && ++b || ++c;
```

        printf("\n%d%d%d%d", a,  b, c, d);

```
    }
```

a) 6 -6 0 0
b) 6 -5 0 1
c) -6 -6 0 1
d) 6 -6 0 1

. What is the output of this C code?

```
 #include <stdio.h>
```
```
    void main()
```
```
    {
```
```
        int a = -5;
```
```
        int k = (a++, ++a);
```
```
        printf("%d\n", k);
```
```
    }
```

a) -4
b) -5
c) 4
d) -3

What is the difference between the following 2 codes?

```
    #include <stdio.h> //Program 1
```
```
    int main()
```
```
    {
```
```
        int d, a = 1, b = 2;
```
```
        d =  a++ + ++b;
```
```
        printf("%d %d %d", d, a, b);
```
```
    }
```

```
    #include <stdio.h> //Program 2
```
```
    int main()
```
```
    {
```
```
        int d, a = 1, b = 2;
```
```
        d =  a++ +++b;
```
```
        printf("%d %d %d", d, a, b);
```
```
    }
```

a) No difference as space doesn’t make any difference, values of a, b, d are same in both the case
b) Space does make a difference, values of a, b, d are different
c) Program 1 has syntax error, program 2 is not
d) Program 2 has syntax error, program 1 is not

What is the output of this C code?

```
    #include <stdio.h>
```
```
    int main()
```
```
    {
```
```
        int a = 1, b = 1, c;
```
```
        c = a++ + b;
```
```
        printf("%d, %d", a, b);
```
```
    }
```

a) a = 1, b = 1
b) a = 2, b = 1
c) a = 1, b = 2
d) a = 2, b = 2

Tuesday, 27 January 2015

Formatted I/O functions in C

printf() function:

printf() function is used to print the “character, string, float, integer, octal and hexadecimal values” onto the output screen.
We use printf() function with %d format specifier to display the value of an integer variable.
Similarly %c is used to display character, %f for float variable, %s for string variable, %lf for double and %x for hexadecimal variable.
To generate a newline,we use “\n” in C printf() statement.

Example program for C printf() function:

#include <stdio.h>
int main()
{
char ch = ‘A’;
char str[20] = “fresh2refresh.com”;
float flt = 10.234;
int no = 150;
double dbl = 20.123456;
printf(“Character is %c \n”, ch);
printf(“String is %s \n” , str);
printf(“Float value is %f \n”, flt);
printf(“Integer value is %d\n” , no);
printf(“Double value is %lf \n”, dbl);
printf(“Octal value is %o \n”, no);
printf(“Hexadecimal value is %x \n”, no);
return 0;
} .

Output:

Character is A String is fresh2refresh.com Float value is 10.234000 Integer value is 150 Double value is 20.123456 Octal value is 226 Hexadecimal value is 96 .

You can see the output with the same data which are placed within the double quotes of printf statement in the program except

%d got replaced by value of an integer variable (no),

%c got replaced by value of a character variable (ch),

%f got replaced by value of a float variable (flt),

%lf got replaced by value of a double variable (dbl),

%s got replaced by value of a string variable (str),

%o got replaced by a octal value corresponding to integer variable (no),

%x got replaced by a hexadecimal value corresponding to integer variable

\n got replaced by a newline.

C – printf and scanf

printf() and scanf() functions are inbuilt library functions in C which are available in C library by default. These functions are declared and related macros are defined in “stdio.h” which is a header file.
We have to include “stdio.h” file as shown in below C program to make use of these printf() and scanf() library functions.

1. C printf() function:

printf() function is used to print the “character, string, float, integer, octal and hexadecimal values” onto the output screen.
We use printf() function with %d format specifier to display the value of an integer variable.
Similarly %c is used to display character, %f for float variable, %s for string variable, %lf for double and %x for hexadecimal variable.
To generate a newline,we use “\n” in C printf() statement.

Note:

C language is case sensitive. For example, printf() and scanf() are different from Printf() and Scanf(). All characters in printf() and scanf() functions must be in lower case.

Example program for C printf() function:

Output:

Character is A String is fresh2refresh.com Float value is 10.234000 Integer value is 150 Double value is 20.123456 Octal value is 226 Hexadecimal value is 96 .

You can see the output with the same data which are placed within the double quotes of printf statement in the program except

%d got replaced by value of an integer variable (no),

%c got replaced by value of a character variable (ch),

%f got replaced by value of a float variable (flt),

%lf got replaced by value of a double variable (dbl),

%s got replaced by value of a string variable (str),

%o got replaced by a octal value corresponding to integer variable (no),

%x got replaced by a hexadecimal value corresponding to integer variable

\n got replaced by a newline.

2. C scanf() function:

scanf() function is used to read character, string, numeric data from keyboard
Consider below example program where user enters a character. This value is assigned to the variable “ch” and then displayed.

Then, user enters a string and this value is assigned to the variable ”str” and then displayed.

Example program for printf() and scanf() functions in C:

#include <stdio.h> int main() { char ch; char str[100]; printf(“Enter any character \n”); scanf(“%c”, &ch); printf(“Entered character is %c \n”, ch); printf(“Enter any string ( upto 100 character ) \n”); scanf(“%s”, &str); printf(“Entered string is %s \n”, str); } .

Output:

Enter any character a Entered character is a Enter any string ( upto 100 character ) hai Entered string is hai .

The format specifier %d is used in scanf() statement. So that, the value entered is received as an integer and %s for string.
Ampersand is used before variable name “ch” in scanf() statement as &ch.
It is just like in a pointer which is used to point to the variable.

Variations in Output for integer an floats

Integer and floating-points can be displayed in different formats in C programming as:

#include<stdio.h>
int main(){
    printf("Case 1:%6d\n",9876);      
/*  Prints the number right justified within 6 columns  */
    printf("Case 2:%3d\n",9876);      
/* Prints the number to be right justified to 3 columns but, there are 4 digits so number is not right justified  */
    printf("Case 3:%.2f\n",987.6543);
/* Prints the number rounded to two decimal places */
    printf("Case 4:%.f\n",987.6543);
/* Prints the number rounded to 0 decimal place, i.e, rounded to integer */
    printf("Case 5:%e\n",987.6543);
/* Prints the number in exponential notation(scientific notation) */
    return 0;
}

Output

Case 1:  9876
Case 2:9876
Case 3:987.65
Case 4:988
Case 5:9.876543e+002

Unformatted Input/Output Functions with Example: C Language

There are several standard library functions available in this category - those that can deal with a single character and those that can deal with a string of characters. The various unformatted input/output functions in C are shown below:

getchar( ) and putchar( )

Even though getchar( ) and putchar( ) looks like functions, they are not. They are the macros that are used to read and display a character. The syntax to read a character shown below:

“ch = getchar( )” will reads a character from the keyboard and copy it into memory area which is identified by the variable ch. No arguments are required for this macro. Once the character is entered from the keyboard, the user has to press Enter key.

“putchar(ch)” outputs a character stored in a variable on the monitor. The variable should be passed as parameter as shown in the above syntax.

Example1
main()
{
char ch;
clrscr();
ch = getchar();
putchar(ch);
getch();
}

getch(), getche() and putch()

The functions getch() and getche() are used to read a character from the keyboard, similar to getchar(). Both functions don’t need a return key pressed to terminate the reading of a character. A character entered will itself terminates reading.

In case of getch(), the character entered is not displayed or echoed on the screen, whereas in getche(), the character entered is echoed or displayed on the screen. Syntax for both the macros

ch = getch(); /*Typed character will not be displayed on the screen*/
ch = getche(); /*Typed character will be displayed on the screen*/

Now, we have to display the inputted character on the screen, putch() macro is introduced.
“putch(ch)” This function outputs a character stored in the memory, on the monitor. The variable should be passed as parameter to the functions. In the above syntax ‘ch’ is used as an argument and its value is displayed on the screen.

Example2:
main()
{
char ch;
clrscr();
ch = getche();
putch(ch);
getch();
}

gets() and puts()

These functions are used to read a set of characters (string) from the keyboard and display a set of characters (string) on the screen.

char str[5];
gets(str); /* Reads a set of characters into memory area str */
puts(str); /* Displays a set of characters from memory area str */
Example3
main()
{
char str[10];
clrscr();
gets(str);
puts(str);
getch();
}