for loop

The “for loop” loops from one number to another number and increases by a specified value each time.
The “for loop” uses the following structure:

      for (Start value; continue or end condition; increase value)
     		statement;

Look at the example below:

	#include<stdio.h>

	int main()
	{
     		int i;
     		for (i = 0; i < 10; i++)
     		{
          		printf ("Hello\n");
         		printf ("World\n");
     		}
     	return 0;
	}

Note: A single instruction can be placed behind the “for loop” without the curly brackets.

In the example we used i++ which is the same as using i = i + 1. This is called incrementing. The instruction i++ adds 1 to i. If you want to subtract 1 from i you can use i--. It is also possible to use ++i or --i. The difference is is that with ++i (prefix incrementing) the one is added before the “for loop” tests if i < 10. With i++ (postfix incrementing) the one is added after the test i < 10. In case of a for loop this make no difference, but in while loop test it makes a difference. But before we look at a postfix and prefix increment while loop example, we first look at the while loop.

The while loop

The while loop can be used if you don’t know how many times a loop must run. Here is an example:

	#include<stdio.h>

	int main()

	{
    		int counter, howmuch;

    		scanf("%d", &howmuch);
    		counter = 0;
    		while ( counter < howmuch)
    		{
          		counter++;
          		printf("%d\n", counter);
    		}
    		return 0;
	}

Let’s take a look at the example: First you must always initialize the counter before the while loop starts ( counter = 1). Then the while loop will run if the variable counter is smaller then the variable “howmuch”. If the input is ten, then 1 through 10 will be printed on the screen. A last thing you have to remember is to increment the counter inside the loop (counter++). If you forget this the loop becomes infinitive.

As said before (after the for loop example) it makes a difference if prefix incrementing (++i) or postfix incrementing (i++) is used with while loop. Take a look at the following postfix and prefix increment while loop example:

 

C - Functions

A function is a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division usually is so each function performs a specific task.

A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C standard library provides numerous built-in functions that your program can call. For example, function strcat() to concatenate two strings, function memcpy() to copy one memory location to another location and many more functions.

A function is known with various names like a method or a sub-routine or a procedure, etc.

Defining a Function:

The general form of a function definition in C programming language is as follows:

return_type function_name( parameter list )
{
   body of the function
}

A function definition in C programming language consists of a function header and a function body. Here are all the parts of a function:

• Return Type: A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.
• Function Name: This is the actual name of the function. The function name and the parameter list together constitute the function signature.
• Parameters: A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.
• Function Body: The function body contains a collection of statements that define what the function does.

  Example:

  Following is the source code for a function called max(). This function takes two parameters num1 and num2 and returns the maximum between the two:

  /* function returning the max between two numbers */
  int max(int num1, int num2) 
  {
     /* local variable declaration */
     int result;
   
     if (num1 > num2)
        result = num1;
     else
        result = num2;
   
     return result; 
  }

  
  

C - Arrays

C programming language provides a data structure called the array, which can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.

Declaring Arrays

To declare an array in C, a programmer specifies the type of the elements and the number of elements required by an array as follows:

type arrayName [ arraySize ];

example---double balance[10];
 

Initializing Arrays

You can initialize array in C either one by one or using a single statement as follows:

double balance[5] = {1000.0, 2.0, 3.4, 7.0, 50.0};

The number of values between braces { } can not be larger than the number of elements that we declare for the array between square brackets [ ].

#include <stdio.h>
 
int main ()
{
   int n[ 10 ]; /* n is an array of 10 integers */
   int i,j;
 
   /* initialize elements of array n to 0 */         
   for ( i = 0; i < 10; i++ )
   {
      n[ i ] = i + 100; /* set element at location i to i + 100 */
   }
   
   /* output each array element's value */
   for (j = 0; j < 10; j++ )
   {
      printf("Element[%d] = %d\n", j, n[j] );
   }
 
   return 0;
}

When the above code is compiled and executed, it produces the following result:

Element[0] = 100
Element[1] = 101
Element[2] = 102
Element[3] = 103
Element[4] = 104
Element[5] = 105
Element[6] = 106
Element[7] = 107
Element[8] = 108
Element[9] = 109

Tricky Questions or Puzzles in C

1) WTAHT will be the output of the following Printf function.
  printf("%d",printf("%d",printf("%d",printf("%s","ILOVECPROGRAM"))));

Ans-ILOVECPROGRAM1321

The above printf line gives output like this because printf returns the number of character successfully written in the output.So the inner printf("%s","ILOVECPROGRAM") writes 13 characters to the output so the outer printf function will print 13 and as 13 is of 2 characters so the next outer printf function will print 2 and then next outer printf will print 1 as 2 is one character.So is the output 1321

2-Write code snippets to swap two variables in five different ways.

Answer:

a.      /* swapping using three variables*/ (Takes extra memory space)

Int a=5, b=10, c;

c=a;

a=b;

b=c;

b.      /* using arithmetic operators */

a=a+b;

b=a-b;

a=a-b;

c.       /* using bit-wise operators */

a=a^b;

b=b^a;

a=a^b;

Line	Operation	Value of a	Value of b
1	-	5	10	Initial values
2	a=a^b	15	10
3	b=a^a	15	5
4	a=a^b	10	5	values after swapping

d.      /* one line statement using bit-wise operators */ (most efficient)

a^=b^=a^=b;

The order of evaluation is from right to left. This is same as in approach (c) but the three statements are compounded into one statement.

e.       /* one line statement using arithmetic & assignment operators */

a=(a+b) - (b=a);

In the above axample, parenthesis operator enjoys the highest priority & the order of evaluation is from left to right. Hence (a+b) is evaluated first and replaced with 15. Then (b=a) is evaluated and the value of a is assigned to b, which is 5. Finally a is replaced with 15-5, i.e. 10. Now the two numbers are swapped.

3-  Find the maximum & minimum of two numbers in a single line without using any condition & loop.

Answer:

void main ()

{

int a=15, b=10;

printf (“ max = %d, min = %d”, ((a+b) + abs(a-b)) /2, ((a+b) – abs (a-b)) /2);

}

4.  How to print number from 1 to 100 without using conditional operators.

Answer:

void main ()

{

int  i=0;

while (100 – i++)

printf (“ %d”, i);

}

1.     #include <stdio.h>

2.     printf("%.0f", 2.89);

a. 2.890000
b. 2.89
c. 2
d.3 

 Answer

Answer:d

5-#include<stdio.h>

int main(){

    int i,j,k;

    for(i=0,j=2,k=1;i<=4;i++){

         printf("%d ",i+j+k);

    }

return 0;        

}

Output: 3 4 5 6 7

c-loops

There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Programming languages provide various control structures that allow for more complicated execution paths.

A loop statement allows us to execute a statement or group of statements multiple times and following is the general form of a loop statement in most of the programming languages:

C programming language provides the following types of loop to handle looping requirements. Click the following links to check their detail.

Loop Type	Description
while loop	Repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body.
for loop	Execute a sequence of statements multiple times and abbreviates the code that manages the loop variable.
do...while loop	Like a while statement, except that it tests the condition at the end of the loop body
nested loops	You can use one or more loop inside any another while, for or do..while loop.

Loop Control Statements:

Loop control statements change execution from its normal sequence. When execution leaves a scope, all automatic objects that were created in that scope are destroyed.

C supports the following control statements. Click the following links to check their detail.

Control Statement	Description
break statement	Terminates the loop or switch statement and transfers execution to the statement immediately following the loop or switch.
continue statement	Causes the loop to skip the remainder of its body and immediately retest its condition prior to reiterating.
goto statement	Transfers control to the labeled statement. Though it is not advised to use goto statement in your program.

C - Decision Making

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

Following is the general form of a typical decision making structure found in most of the programming languages:

C programming language assumes any non-zero and non-null values as true, and if it is either zero ornull, then it is assumed as false value.

C programming language provides following types of decision making statements. Click the following links to check their detail.

Statement	Description
if statement	An if statement consists of a boolean expression followed by one or more statements.
if...else statement	An if statement can be followed by an optional else statement, which executes when the boolean expression is false.
nested if statements	You can use one if or else if statement inside another if or else if statement(s).
switch statement	A switch statement allows a variable to be tested for equality against a list of values.
nested switch statements	You can use one switch statement inside another switchstatement(s).