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R. Subburaj, Programming in C Vikas Publshing House Pvt. Ltd, New Delhi 2

Loop with if using goto and label

Example : Demonstrates use of if for iteration

#include

int main()

{

int sum=0, i=1; /*declaration and

initialization combined*/

Step3: /*label- loop starts here*/

if (i

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{sum= sum+i;

i=i+1;

goto step3;}

printf(sum of first 10 natural numbers=%d\n,sum);

}Result:

sum of first 10 natural numbers=55

Loops (Contd.)

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for (exp1; exp2; exp3)

{statements; }

Note the keyword, the parentheses andsemicolons. No semicolon after exp3.

exp1, exp2 and exp3 are expressions.exp1 contains the initial value of an indexor a variable.

exp3 contains the alteration to the indexafter each iteration of the body of the forstatement.

for statement

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The body of the statement is either a singlestatement or group of statements enclosedwithin braces.

If a single statement has to be executed thenbraces are not required.

exp2 condition that must be satisfied if thebody of statements are to be executed.

An example of a for loop is given below:

for (i=0; i

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int main(){

int sum=0, i=0; /*declaration and initializationcombined*/

for (i=1; i

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Exercise

What change will you make if we want to

add 100 numbers and 1000 numbers ?

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Three Components of for

exp1 and exp3 are assignments or function calls.

exp2 is a relational expression. The three

expressions may not always be present.However, even if an expression is not present,

the associated semicolon should be present.

For instance,

for (;exp2;)

{s1}

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Finding all even numbers

int main ()

{

int i=2;

for (; i

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Symbolic Constants

# define name constant

Not variables and hence they are not defined as

part of the declarations of variables.

Specified on top of the program before themain()

Wherever the symbolic constant names appear

in the program, the compiler will replace them

with the corresponding replacement constants.

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#define LOW 100

#define UPPER 150

#define STEP 1

int main(){

int num;

for (num=LOW; num

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Nested for Loop

Example

for (i=1;i

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while loop

Subset of for loop{

exp1;

while (exp2)

{

statements

exp3;

}}

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Reversing a number

#include

int main(){ long unsigned n, reverse;

printf(enter the number to bereversed\n);

scanf(%lu, &n);reverse=0;

while (n>0)

{ reverse=reverse*10+ (n%10);

n=n/10; }printf(Reversed number=%lu, reverse);

}

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Structure of while

TRUE FALSEWhilecondition

ST

AT

EMENT

SSTATEMENTS

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do. while

TRUE

FALSE

While

condition

STATEMENTS

DO

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Example of do.while

#include

#include

main()

{ int alpha=0;

do{ printf (\nenter upper case alphabet- enter1 to quit\n);

if (alpha >=A && alpha

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Example of do.while

else

{ if(alpha==1)

printf(End of Session);

elseprintf(\ninvalid entry; retry);

}

}while(alpha!=1);}

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Linear Search

Algorithm

Declarationarray ia of size n, i = 0

item to be searched = x

found = false

do

if (ia[i] == x) then

found = true

elsei = i + 1

while (i

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Switch

Enables multi-way decision making

More powerful than if .. else Syntax of switch statement is given below.

switch (expression)

{

case constant or expression : statements

case constant or expression : statements

..

Default : statements }Constant expressions following case should be

unique.

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Example of Switchint main()

{ int a;

char ch = c;

while (ch==c)

{ printf(\nEnter a digit 0 to 9\n);

scanf(%d,&a);

switch(a)

{ case 0:printf(Zero\n);break;

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Example of Switch (contd.)

case 1:printf(One\n);

break;case 2:printf(Two\n);

break;

case 3:printf(Three\n);

break;case 4:printf(Four\n);

break;

case 5:printf(Five\n);

break;case 6:printf(Six\n);

break;

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Example of Switch (contd.)

case 7:printf(Seven\n);

break;case 8:printf(Eight\n);

break;

case 9:printf(Nine\n);

break;default:printf(Illegal character\n); }

printf(enter c if you want to continue\n);

printf(or any other character to end\n);

ch=getche();

if(ch!=c)

printf(End of Session); } }

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Switch with char

char m;switch(m)

{

case a : s1;

break;

case b : s2;

break ;

}

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SWITCH with char (contd.)

int op;

switch(op)

{

case + : s1;break;

case / : s2;

break ;}

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Break, Continue, Return

Break causes the program to break from the loop that

encloses it and proceed to the next stage of theprogram

Continue causes resuming next iteration of the loop.

Return may appear anywhere in the program

int main()

{ int a;

do

{ printf(enter a number-enter 0 to end session\n);

scanf(%d, &a);

if(a>20000)

{ printf(you entered a high value-going outof range\n); break; }

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Break, Continue, Return (contd)

else

if(a>0)printf(you entered %d\n, a);

if (a

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Result of program

Enter a number-enter 0 to end session

33

You entered 33


-60

You entered a negative number

Enter a number-enter 0 to end session45

You entered 45


25000

You entered a high value-going out of range

End of session

* exit() function

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30

8. Arrays

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User defined data type

Contains data of the same type

Array of integers, array of double etc.

A = {2,4,6,8}

A[0]=2

A[1]=4

A[2]=6

A[3]=8

Arrays

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Eg. double emp_age [100];

allots memory size of 100 doubles contiguously.

If emp_age[0] is stored in location 1000 then

emp_age[n] will be stored in 1000 + n * 8 (size

of variable).

[100] is called subscript.

Initialization

Double emp_age[5] = {30.1, 31.1, 35.1, 36.1, 37.1];

Double emp_age[] = {30.1, .. 37.1};

Array Declaration

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{ int s1[10];int i;

printf(Enter 10 integers \n);

for (i=0; i

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Finding greatest numberand position in a Array

int main(){ int a[5]={1,5,2,6,3};

int max=0, i, ind=0;

for(i=0; i max)

{ max =a[i];

ind=i+1; }

}

printf(maximum number=%dlocation=%d\n, max,ind);

}

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Strings String is an array of characters

char name{25};

scanf(%s, name);

The syntax for gets is: gets(name);

puts(name);

puts (Enter the word);

printf canbe used to print more than one variable and scanf to getmore than one variable at a time, in a single statement. However,puts can output only one variable and gets can input only onevariable in one statement. In order to input or output more thanone variable, separate statements have to be written for eachvariable. gets and puts are unformatted I/O functions

Use to use string related library functions

Eg. strlen(str) returns length of str.

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Palindrome#define FALSE 0

int main()

{ int flag=1;

int right, left, n;

char w[50]; /* maximum width of string50*/

puts(Enter string to be checked forpalindrome);

gets(w);

n=strlen(w)-1;

for ((left=0, right=n); left

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Palindrome

if (flag)

{ puts(w);

puts(is a palindrome);

}

else

printf(%s is NOT a palidrome);

}

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Multi-Dimensional Arrays Multi-dimensional Arrays are stored row by rowcontinuously.

int main()

{ int i,j;

int z[2][2];

int x[2][2] = {1,2,3,4};

int y[2][2] = {5,6,7,8};

for (i=0; i

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Binary SearchPre-condition : Data already sorted.

Algorithm for Binary Search

int a[n];

left = 0

right = n-1

found = false;

while (left

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40

9. Functions

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Modular Programming Concept

MAIN

f1 f2 f3 f4

f11 f12 f21 f31

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Structured programming Code

of good programming practices

Write only one statement per line

Coin meaningful names for constants, variables

and functions

Use capitals for names of constants

Divide programs into functions

Each function performs one task

Each function must have atleast one comment

statement Skip a line between functions

Skip a line after declaration statements in the main

function as well as each function

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Structured programming Code

of good programming practices

Bring clarity by skipping lines wherever required

Put only one brace on each line

Align all opening braces and closing braces

Indent as much as possible to bring out logicalstructure of the program

Some of the program statements that could be

indented are body of function, body of loop, body of

if..else statements Indent each case in switch statement

Indent an item within a structure declaration.

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Three Parts of Function

A function consists of three parts :

a) Function Declaration

b) Function Definitionc) Function Call

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Function Declaration

return data type function name

(formal argument 1, argument 2,. ) ;

Example

float f1 (float arg 1, int arg 2);

void fun2 (float arg1, int arg2); /*void

means nothing*/

char fun3(float arg1, int arg2);

char fun4();

Also called function prototype.

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Function Definition

Can be located anywhere.

Consists of 2 parts

Function declarator or header

Conforms to proto, no semicolon

Function body

Consists of local variables &

statements

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Algorithm for function add

main function

Step 1 define function add

Step 2 get 2 integers

Step 3 call add & pass the 2 values

Step 4 get the sumStep 5 Print the value

Function Add

Step 1 get the values

Step 2 add them

Step 3 return the value to main function

P f ddi

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Program for addingint main()

{ int a=0, b=0, sum=0;int add(int x, int y); /*function declaration*/

printf(enter 2 integers\n);

scanf(%d%d, &a, &b);

sum=add(a,b); /*functon call*/printf(sum of %d and %d=%d, a,b,sum); }

/* function definition*/

Int add (int c, int d) /* function declarator*/

{ int e;e=c+d;

return e; }

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A F ti ll d ti

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A Function called many times{ float a,b,c,d, sum1, sum2, sum3;

float add(float a, float b); /* function declaration*/

printf(enter 2 float numbers\n);scanf(%f%f, &a, &b);

sum1 = add(a,b); /*function call*/

printf(enter 2 more float numbers\n);

scanf(%f%f, &c, &d);

sum2 = add(c,d); /* function call*/sum3=add(sum1,sum2);

printf(sum of %f and %f=%f\n, a,b,sum1);

printf(sum of %f and %f=%f\n, c,d,sum2);

printf(sum of %f and %f=%f\n, sum1,sum2,sum3); }

/*function definition*/

float add (float c, float d) /* function declarator*/

{ float e;

e=c+d;

return e; }

C lli lti l f ti

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Calling multiple functions

Step 1 : get the number

Step 2 : if number is odd call the Reverse functionStep 3 : else multiply the number by 2

Step 4 : if number is evenly divisible by 3 call ADD-digits

Reverse Function

Step 1 : reverse = 0Step 2 : while (number > 0)

reverse = reverse * 10 + (number % 10)

number = number/10

Step 3 : return (reverse)

C lli lti l f ti (C td )

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ADD-digits function

Step 1 : sum = 0

Step 2 : while number > 0

sum = sum + (number % 10)

number = number / 10

Step 3 : return (sum)

Look at Example 44 in page 146.

Calling multiple functions (Contd.)

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Scope of the variable is local to the function,

unless it is global

Look at Example 45 in page 149.

To find the greatest number in an array, look

at Example 46 in page 151.

To reverse a string, look at Example 47 in

page 152.

Scope rules for functions

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return (sum);

return v1;

return true;

return `Z;

return 0;

return 4.0 + 3.0; etc.

return;

Return values

cprogram7

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