C Programming

Input output Conditional statements and Iterative statements

Rohit Khokher

Input & output in C

• Reading a Character from a keyboard– variable_name =getchar ();

#include <stdio.h>void main (){char x;x= getchar ();printf (“\n Input = %c”,x)}

• Writing a character one at a time to screen.– variable_name =putchar();

#include <stdio.h>void main (){char x;x= getchar ();putchar (x};putchar (‘\n’);}

Formatted Input

Data represented in a format as shown below:A 15.75 123 John

Real number with two decimal digits

IntegerString

%wd

Format specification

Fieldwidth

Specifies a data to be read

%f

Specifies a real data to be read

Character

%wc%ws

scans (“format control string”, arg1,arg2, arg3, …, arg n)

A 15.75 123 John

char x;float y;int z;char name[3];scanf(“%c %f %d %s”, x, &y, &z, name);

scanf accepts the address of y and z so we need & operator that gives the address of the variables y and z.

String and character type declarations provide the address of the first character so we don’t need &.

%c Read a single character

%d Read a decimal integer

%f Read a floating point value

%e Read a floating point value

%g Read a floating point value

%h Read a short integer

%i Read a decimal, hexadecimal or octal integer

%o Read an octal integer

%s Read a string

%u Read an unsigned decimal integer

%x Read a hexadecimal integer

%[..] Read a string of words

Commonly used scanf format code

Formatted outputscans (“format control string”, arg1,arg2, arg3, …, arg n)

Display heading specificationDisplay format specification Escape sequences \n, \t, \b

“The out put of the program is”

Integer %wdReal numbers %w.pf or w.pe where w>=p+7

String %w.ps or %wc

%c Print a single character

%d Print a decimal integer

%f Print a floating point value

%e Print a floating point value

%g Print a floating point value

%h Print a short integer

%i Print a decimal, hexadecimal or octal integer

%o Print an octal integer

%s Print a string

%u Print an unsigned decimal integer

%x Print a hexadecimal integer

Commonly used printf format code

Decision making & branching

if statement

Switch statement

Conditional operator statementgoto statement

Simple if statement

if …else statement

Nested if …else statement

else if ladder

Simple if statement Example

General form

if( test expression){

statement-block;

}

. . .…If ( a==b){

x=a*b+20;y=b/x;

}….…..

Decision making & branching

• if …. else statement • Example

General form

If ( test expression){

True -block;}Else{

False-block;}

. . .If ( a==b){

x=a*b+20;y=b/x;

}else{

z=a/b;}

Decision making & branching

• Nesting of if …. else statement

if ( test expression 1) { if ( test expression 2)

{True -block;

}else{

False-block;}

else { }

if ( A> B ) { if ( A>C) { printf ( “%f\n”,A);} else {printf ( “%f\n”,C);} else { if ( B>C) {printf ( “%f\n”,B);}else{printf ( “%f\n”,C); }}

if ( test expression 1) statement 1; else if ( test expression 2)

statement 2; else if ( test expression 3)

statement 3; else statement 4;

• The else if ladder

if ( m > 79) printf(“\n Honours”); else if (m>59)

printf(“\n First”); else if ( m>49) printf(“\n Second”); else printf(“\n Fail”);

The switch statementswitch (expression){

case value :block;break;

case value :block;break;

…………….……………..default:

block;break;

}

switch (i){ case 10 :

block;break;

case 9:block;break;

default:block;break;

}

switch (ch){ case ‘A’ :

block;break;

case ‘B’:block;break;

default:block;break;

}

Iteration (Looping)

sum =0;label:

sum=sum+1;if (sum <5){ goto label;

}

Sum012345

While & do while

• while (expression){

...block of statements to execute...

• }

• do{

block of code

} while (condition is satisfied);

Example while & do while loop

#include <stdio.h>int main(void)

{int loop = 0;while (loop <=10){ printf(“%d”, loop);

++loop}

return 0; }

#include <stdio.h>int main(void){ int value, r_digit;printf(“enter a number to be reversed.\n”);scanf(%d, &value);do{ r_digit = value % 10;printf(“%d”, r_digit);value = value / 10;} while (value != 0);printf(\n);return 0; }

Algorithm tracing

. . . . . . . . value =986do{r_digit = value % 10;printf(“%d”, r_digit);value = value / 10;} while (value != 0);

. . . . . . . . . . . . .

value r_digit

986 6

98 8

9 9

0

For loop

for (expression_1; expression_2;expression_3){...block of statements to execute...}

for (count = 1; count <=10; count = count +1) printf(“%d”, count);

for (count = 1; count <=10; count = count + 1) { printf(“%d”, count); printf(“\n”); }

Example for loop

#include <stdio.h>int main(void)

{ int count;for (count = 1; count <=10; count = count + 1)

printf(“%d”, count);printf(“\n”);return 0;

}

Example for loop #include <stdio.h>  void main(){    // using for loop statement   int max = 5;    int i = 0;    for(i = 0; i < max;i++){       printf("%d\n",i);      } }

Example do while

#include <stdio.h> void main(){    int x = 5;    int i = 0;    // using do while loop statement     do{        i++;        printf("%d\n",i);     }while(i < x);   }

Loop with break#include <stdio.h> void main(){   int x = 10;   int i = 0;     // when number 5 found, escape loop body    int numberFound= 5;    int j = 1; .    while(j < x){       if(j == numberFound){             printf("number found\n");

            break;         }         printf("%d...keep finding\n",j);       j++;     }       }