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languages C language does not have any built-in input-output wo)
Unlike other programming \
stements 05 & of its syntax.
wr 0 and mers ‘There are several other functions, which are also used for I/O operations in
C. These function calls are collectively called as Standard 1/O library. In this chapter, we shall
deal with the common V/O functions that are widely used,
. All 1/0 operations are carried out through function calls such as
3.1 Input data
‘The input data has to be arranged in a particular format. ‘The input data may: contain a mixed mode
data, such as
101.75 225 R
; The above line contains three pieces of data arranged ina particular format, The first part of
this data is read as ‘float’, the second part as ‘int’ and the third part as ‘char’. To make this
possible, we will be using a function. called scanf () - 3.4 Output operations
This the wish of any programmer to get the output results in a most understandable form. Hence
‘any output format has to be user friendly.
\ ‘The output format will be similar to the input one and printf function is used for this purpose, calling it so is that it has rich
e branched as Conditional
ments it has if and switch.
and do-while.
Cis considered as a structured language, and one of the reasons for
1 statements. The control statements can bi
and varied program contro:
and Unconditional control Statements. Under conditional control state!
The Unconditional statement is goto. The loop constructs are while, for,
The control statements are widely used to support decision-making processes. They largely
rely upon a conditional test that determines the decision.
4.1 IF statement .
This is the most powerful conditional control statement. The if statement can be used in different
forms, depending upon the nature of the conditional test, and the main forms are:
+ Simpleif
+ Blockif
+ Nested if
‘We shall discuss different “if” constructs in the following sections.
4.2. Simple if statement
The general form of simple if statement is
+ ifftest expression)
|
|
:
| {e.g.) :
: if («> y)
| * prinif(* x is greater than y \n");
i
if soles >1000 && sales <= 2000 )
d first. Mit Tetums truc then the statement followed by it
ntro eae to the next statement. 42. © Programming inc
Calculate the sales commission for the data given below:
Sales value(Rs)
Less than 1000 /=
Above 1000 but below 2000
Above 2000 but below $000
Above 5000
Solution
First let us solve it by using simple if ‘construct,
Commission %
No commission
5% of sales
8% of sakes
10% of sales
/* Example Program ~ Using’ simple if construct W
include
vold main()
{
float sales, com;
Printf(*Enter sales value \n’);
scant("%F*,&sales);
U(sales <= 1000)
coma;
if ( soles > 1000 ag soles <=
com = soles * 0.05;
2000)
If (sales > 2000 && soles <=5000)
com = sales * 0.08;
i¥ (ales > 5000)
com = gales * 0,10;
‘}
Output
Enter sales value
1000
Commission Rs 0.00
Enter sales value
2500
Commission Rs 200,09
Expla nation
Here, the sales ig Biven as
{s 200, and ifthe sates ae
in the float variable com:
Ad its etored fn the vag st es
le com:
a5 10% of len? Analy if theo
Printf(*\n Commission Re 7.26",
‘nd ifthe sales ia
Hes between 109] St Fintan oF equal
les
scOm);
and 5000, then 896 of sates is caleulst?
exceeds 5000 then
the commniasion ¥ |
|
Control Statements © 4.3
4.3 simple if-else statement
Here an optional clause ‘else’ is used along with the simple if statement. The general form is
if(test_ expression)
stotement;
else
statement;
(e.9.)
if (total >= 250 )
prinif(* result is pass \n"):
else
printf(* result is foil \n");
her the given number is odd or even we use “simple-else-if”
For example to check whetl
onstruct. The complete program is as follows.
/* Program to check odd or even */
#include
void moin()
{
int no,m;
print ("Enter number to check : “);
seant(*%d" ,&n0);
m=no%2;
if(m==1)
print{(’\n Given number is odd”);
else
print{(*\n Given number is even");
}
Output
Enter number to check : 6
Given number is even
Enter number to check : 10
Given number is even
ee program by using miodulo operator the remainder value is find out for the given
Testa na based on that value, program displays whether it is ‘odd or even. This construct is
efull when the else part is having only one statement.
ae Block if statement
it a
a block or a group of statements follows the test expression. The general form is
~ifftest expression)
staiements; 4.7 Looping
Chas powerful looping constructs in it, and this is one form of control statements where we
tready know the number of repetitions. In C there are three looping constructs. They are for,
yhile and do-while.
Let us discuss in the following sections, the looping form of control statements. Please do
member conditional control statements. 4.8 © Programming in C
4.8 For loop ,
The general form of a for loop is,
for {expression 1; expression 2 ; expréssion 3) «
{
}
sequence of statements ;
here
expression | is the initial value
expression 2 is the testing value
expression 3 is the increment(step) value
e.g.)
for (i=0;i<=100; i++)
sum +=;
It may be observed that the following steps are involved, namely:
1. Initialisation
2. Condition checking
3. Body of the loop
4, Increment
5. (again) Conditional
Pleasé note that there is no semicolon after for loop; if there is a semicolon after the for loop
then the loop is said to be a ‘time delay loop’ or ‘software delay ‘ and the construct is given below.
for(i=0;i<100;+ +i) ;
Also by using the comma operator, more than one variable can be initialised as seen
below. B .
for{ fact=i=1; i<10; i++)
fact *= i;
Here, both fact and i are variables that are initialised to 1. Similarly we can have two action
statements as third part of the for loop; one is to calculate the ‘fact’ value and the other is used to
increment the ‘i’ value. The code snippet for the above one is given below
forlfact=i=1; i <=5; fact*=i, i++);
Without the comma operator, the same will be seen as,
foct =1; ~ :
forli=1;i<10;++i)
fact * = j;
Thus, the coding got teduced by using the comma operator,
Insteail of initialising the value inside the for loop,
then the construct is ifwe have the option to initialise it before, Control Statements @ 4.9
already defined outside for
foct* =i .
Bere, the first semicolon in for loop reveals that the initial value is
simarly we can also i amet the index, inside for Loop. Hr Such cases there is noneed for
Tre expression that is used to increment the values within the for loop construct, and the resultant
code isas follows:
fact =i=1;
for (i i<=5;)
fact* =H;
itt:
} | ;
Here, the index value gets incremented inside the for loop as said before. Consider the last
form of for” construct in which the initial value, final value and also increment value are not given
for (i 73
statements;
} : ; :
The above for loop executes infinitely, and the only way to exit the for loop 1 by using the
vchas goto) inside the for loop.
abnormal exit (sus
ping using while
led loop statement i.e. the test condition is evaluate
.s repeated until the test condition
ral form of ‘while’ is:
4.9 Loo!
ed and if itis true the
becomes false; then
“While” isan entry controll:
body of the loop is evaluated. This process i
the control is transferred out of ‘the loop. The gene!
while ( test expression )
{
sequence of statements;
}
In flow chart form
statements
pee ee eee ee ato Progremming in e
following while loop helps us to sum the numbers between land 100
The fol
sum = 0;
i=l;
while (i <=100)
{ ;
sum+ =i
itt;
! i gets initiali i é loop. Now, the test 7
variables sum and i gets initialised before entering the loop. Now, expression
7 ae it returns true then the statements within braces will execute, Note that i gets
eeaeiel inside the loop, ifit is missing then the loop is infinite one since the variable ialways
Jess than 100. se
Consider the following while-loop construct in which the loop is executed infinitely
while. (1}
{
statements ;
}
Again where want to exit from such a loop, we have to use some unconditional statement,
andthe above formis similar to the for loop where we have all the three expressions missing. Also,
note that in C other than 0 all numbers are considered as positive.
4.10Looping using do-while
“do-while” is an exit controlled loop statement i.e. condition is tested only after executing a loop.
Onsome occasions, itmay be necessary to execute the body of the loop, before the testis performed.
Such‘occasion can be handled using do-while. The general form is: :
* do
{
sequence of statements;
} while ( test expression );
Tn flow chart form
[stotements] Control Statements © 4.14
“The following do-while constructs o find the sum of odd mumbers that ae lying between 1 and 100,
sum = 0; i
isl;
do
ecuted first and then, the test condition is evaluated.
even if the test expression returns false. This is
jo-while construct.
Here the statements within the ‘braces are ex
Thus the statements are executed at least once,
the fundamental difference between while and d
4.11 Comparative study of the I
Itis upto the programmer's choice to choose the type of the loop. But before choosing the particular
type, the following points should be considered. If the loop is simple one, we can use “for” loop
control and itis very useful in Arrays. If we want fo execute the Joop atleast once even though the
condition is false then definitely we have to use ‘do-while’ loop structure. If the statements are
ased on certain condition before being executed then ‘while’ loop ‘structure is preferred.
4.12 Break statement
‘An early exit from the loop is possible by a ‘break’
encountered, the loop is immediately exited and the program continues with the
following the loop. The general form is,
while ( test expression }
joop
statement! When a ‘break’ statement is
.e statement immediately
{
}
‘To illustrate the above statement let us consider an example program. In this case we want toadd
only positive integers and neglecting negative values. And when negative numbers are keyed, the loop
should terminate by using break statement and print the sum of all the entered positive integer values.
/* Example program to illustrate break */
#include
void main()
if something break;
int no,sum=0;
prinif("\n Enter no and negative no to exit \n”);
while (1)
scani{?%d",8n0)};
if (no <0)
break; 4.12 @ Programming in C
Output
Enter no and negative no to exit
5
6
8
2
The sum is 19
Here break will terminate the loop when the entered number is less than 0 and print the value
of sum. Thus the break statement will cause program execution to continue after enclosing for,
while, do or switch statement.
4.13 Continue statement
Unlike break statement, which causes the loop to be terminated, the ‘continue’ causes the loop to
be continued with the next iteration after skipping the statements in between, thus by passing the
rest of the loop: The general form is:
for ( expression T ; expression 2 ; expression 3)
if something continue;
}
The following program segment will illustrate the use of continue statement.
Consider the programming situation where we are going to give 5 numbers, and the program
has to add only positive numbers thus neglecting the negative number.
/* Example program to illustrate “continue” */
#include
void main()
{
int i,no,sum=0;
printf(“ \n Enter 5 numbers \n");
for(i=0;i<5;i+ +)
{
scanf("%d",&no);
if (no < 0 ) continue;.
else ‘
sum+=no; Conch travemerts © 4.13
Output
Enter § numbers
4
$
4
al
¥.
Sum of positive numbers 15
Here, the statement “continue” will by-pass all the negative numbers from summning up. The
example program reveals that, continue statement will result in the next iteration of the enclosing
do, while, or for loop to execute, 4.15 Switch statement
This isa multiple branching control statement, and this one is very useful for decision making Whey
more than one case is involved. The general form of the switch statement is
switch (expression)
“ case label 1 :
statement sequence;
break;
case label 2
statement sequence;
7 break; .
case label 3
statement sequence;
breok;
default
statement sequence;
}
‘Switch statement differs from an ‘if’ statement in the way that ‘switch’ can only test for
equality whereas ‘if’ can evaluate for entire given range.
‘When the switch statement is executed, the value of expression is compared against the label
1, label 2, label 3 etc. If a case is found whose value matches with the expression, then the
Sequence of statements that follows the case is executed.
The ‘break’ statement at the end of each block indicates the end of the particular case and
Causes an exit from ‘switch’ statement, thus transferring the control outside switch statement. The
‘default’ statement is.executed if no matches are found and it is optional.
(€.g.) Rewrite the following program using ‘switch’ statement
if (score >= 90)
grade ='q';
else if (score >= 80 )
grade = ‘b’;
e
grade = ‘e; Control Statements © 4.15
solution
ve can use 2 conversion statement sc =
— : ie ore = score /10. The score is an integer and it takes
Marks index
100 10
90-99 2
80-89 8
70-79 7
The program will look like
/* Example program using switch construct Wh
#include
void moin()
{
int marks,index,score ;
printf(*Enter your score“);
sconi(*%d",&score);
score = score /10;
switch (score)
case 10 : index = 10;
break;
cose9 : index = 9;
break ;
cose 8 =: index = 87
break;
case 7: index =.7;
y
print” \n Your index value is %d index);
}
Output
Enter your score 75
Your index value is 7
Enter your score 100
Your index value is 10
re Goto statement
isto aa unconditional statement available in C. Our main aim in the structured programming
eee goto, which may lead to confusion. But, goto statement may be used to exi
layers of nesting. The general form of goto statement is
goto label;
here, label is .
label is an alphanumeric one. 4.16 @ Programming in C
/* Example - goto s:
#include
id main()
{
int x;
printf(“\n. Enter number : “);
scanf("%d",&x};
if (x> 100)
goto err;
printf(“\a Valid input *);
exit{0);
err:
printf(“\n Invalid. input’);
}
Output
Enter number : 56
‘Valid input
Enter number : 123
Invalid input
The use of ‘gots’ is not encouraged since more numb
er of ‘goto’ means more confusion
