Session 3

DATA INPUT AND OUTPUT • As we know that any c program is made up of 1 or

more then 1 function.

• Likewise it use some functions for input output process. The most common function

1) printf() 2) scanf().

printf() Function• printf() function is use to display something on the

console or to display the value of some variable on the console.

• The general syntax for printf() function is as follows

printf(<”format string”>,<list of variables>);

• To print some message on the screen printf(“God is great”);

This will print message “God is great” on the screen or console.

printf() Function

• To print the value of some variable on the screen Integer Variable :

int a=10; printf(“%d”,a);

Here %d is format string to print some integer value and a is the integer variable whose value will be printed by printf() function. This will print value of a “10” on the screen.

printf() function• To print multiple variable’s value one can use

printf() function in following way.

int p=1000,n=5; float r=10.5;printf(“amount=%d rate=%f year=

%d”,p,r,n);

• This will print “amount=1000 rate=10.5 year=5” on the screen

scanf() Function • scanf() function is use to read data from

keyboard and to store that data in the variables. • The general syntax for scanf() function is as

follows. scanf(“Format String”,&variable);

Here format string is used to define which type of data it is taking as input.

this format string can be %c for character, %d for integer variable and %f for float variable.

scanf() Function

scanf(“Format String”,&variable);

• Where as variable the name of memory location or name of the variable

• and & sign is an operator that tells the compiler the address of the variable where we want to store the value.

scanf() Function• For Integer Variable :

int rollno; printf(“Enter rollno=”); scanf(“%d”,&rollno);

Here in scanf() function %d is a format string for integer variable

and &rollno will give the address of variable rollno to store the value at variable rollno location.

scanf() Function

• For Float Variable : float per; printf(“Enter Percentage=”); scanf(“%f”,&per);

• For Character Variable : char ans; printf(“Enter answer=”); scanf(“%c”,&ans);

Single character input – the getchar function :

• Single characters can be entered into the computer using the “C” library function getchar.

• In general terms, a reference to the getchar function is written as.

character variable=getchar();

For examplechar c; c=getchar();

Single character output – The putchar function

• Single character can be displayed (i.e. written out of the computer) using the C library function putchar.

• In general a reference to the putchar function is written as

putchar (character variable);For Example

char c=’a’; putchar(c);

Control Flow In C• Objectives of the module is

1) How to direct the sequence of execution using Decision control Structure

2) Have an understanding of the iterative process using Loop Control Structure

Decision Control StructureThe if-else statement:

• The if-else statement is used to carry out a logical test and then take one of two possible actions depending on the outcome of the test

• Thus, in its simplest general form, the statement can be written.

if(expression) {

statement; }

• The general form of an if statement which include the else clause is

if(expression) {

statement 1; }else {

statement 2; }

If the expression is true then statement 1 will be executed. Otherwise, statement 2 will be executed.

Decision Control Structure

Nested If Elseif<exp1> {

statement1; } else {

if<exp2> {

statement2; }

}

Nested If Else

/* Demonstration of if statement */ #include<stdio.h>void main( ) {

int num ; printf ( "Enter a number :" ) ; scanf ( "%d", &num ) ; if ( num <= 10 )

printf ( “Number is less than 10" ) ; else

printf(“Number is greater than 10”);}

Else if ladderif( expression1 )

statement1;else if( expression2 )

statement2;else

statement3;• For Example

if( age < 18 )printf("Minor");

else if( age < 65 )printf("Adult");

elseprintf( "Senior Citizen");

Decision Control Structure• The switch statement:

causes a particular group of statements to be chosen from several available groups.

• The selection is based upon the current value of an expression that is included within a switch statement.

The general form of switch-caseswitch(expression) {

case expression1: statements; break;

case expression2: statements; break;

case expression3:statements; break;

}

• When switch statement is executed the expression is evaluated and control is transferred directly to the group of statements whose case labels value matches the value of the expression.

switch(choice) {

case ‘r’ : printf(“RED”); break;

case ‘b’ : printf(“BLUE”); break;

default : printf(“ERROR”); break;

}

LOOP CONTROL STRUCTURE • If we want to perform certain action for no of

times or we want to execute same statement or a group of statement repeatedly then we can use different type of loop structure available in C.

• Basically there are 3 types of loop structure available in C

(1) While loop (2) Do..while (3) For loop

While Loop• The while statement is used to carry out

looping operations. • The general form of the statements

initialization; while(exp) {

statement 1; statement 2; increment/ decrement;

}

While loop example#include<stdio.h> void main () {

int digit = 0; while(digit<=9) {

printf(“%d \n”,digit); ++digit ;

} }

Do-While Loop • Sometimes, however, it is desirable to have a loop

with the test for continuation at the end or each pass.

• This can be accomplished by means of the do-while statement.

• The general form of do-while statement is do {

statement1; statement2; increment/decrement operator;

} while(expression);

Do-While Loop Example#include <stdio.h> void main() {

int digit = 0; do {

printf(“%d”, digit++); }while(digit<=9);

}

For Loop• The for statement is another entry controller

that provides a more concise loop control structure.

• The general form of the for loop is :

for(initialization; test condition; inc/decrement) {

statement 1; statement 2;

}

For loop example#include<stdio.h>void main(){

for(x=0; x<9; x++) {

printf(“%d”, x); printf(“\n”);

}}

Reverse For loop • The for statement allows for negative

increments. • For example, the loop discussed above can be

written as follows:

for(x=9; x>=0; x--) {

printf(“%d”,x);printf(“/n”);

}

BREAK STATEMENT• The break statement is used to terminate

loops or to exit a switch.

for(i=1; i<=10; i++) {

if(i==5) break;

printf(“\nI=%d”,i); }

CONTINUE STATEMENT• The continue statement is used to skip or to bypass

some step or iteration of looping structure.

for(i=1; i<=10; i++) {

if(i<5) continue;

printf(“\ni=%d”,i); }

The output of the above program will be 6,7,8,9,10.

THE GOTO STATEMENT • The goto statement is used to alter the normal

sequence of program execution by transferring control to some other part of the program.

• In its general form the goto statement is written as

goto label; • Where label is an identifier used to label the

target statement to which control will be transferred.

goto examplevoid main() {

for(i=0;i<5;i++){

printf(“i =%d”,i);if(i==4)

goto stop;}

stop: printf_s( "Jumped to stop”); }