Control Statements in C Programming
1
Developed by Mr. Sandeep G. Shukla
Control Statement
In programming we need to sometimes control the flow of
operation other than just the sequential statements. In this
case we need the control statements.
Control statements are classified into two viz. the
iterative
statements
and
conditional statement.
Iterative statements
are use to perform certain operation
repetitively for certain number of times. In C we have three
iterative statement viz.
for loop
,
while loop
and
do-while
loop
.
Conditional statements
are use to perform the
operations based on a particular condition i.e. if a
condition is true perform one task else perform another
task. In C we have two conditional statement namely
if-
else
statement and
switch-case
statements.
2
FOR LOOP IN C
A for loop is a repetition control
structure that allows you to efficiently
write a loop that needs to execute a
specific number of times.
Syntax:
The syntax of a
for loop in C
programming language is:
for
(
init
;
condition
;
increment
)
{statement(s);
}
3
Ex. Write a program in c to generate first 20
Fibonacci numbers
#include<stdio.h>
#include<conio.h>
void main()
{int a=0, b=1,c,i,n=20;
printf(“ Fibonacci Series”);
printf(“\n %d \n %d”,a,b);
for(i=1; i<=n-2; i++)
{c=a+b;
printf(“\n%d”,c);
a=b;
b=c;
}
getch();
}
4
Fibonacci Series
0
1
1
2
3
5
8
13
21
34
55
89
144
233
377
610
987
1597
2584
4181
WHILE LOOP IN C
A while loop statement in C
programming language repeatedly
executes a target statement as long as a
given condition is true.
Syntax:
T he syntax of a
while loop in C
programming language is:
while
(
condition
)
{statement(s);
}
5
Ex. Write a C program to generate prime numbers
between 1 to n.
#include<stdio.h>
#include<conio.h>
void main()
{int i,n,x=1;
clrscr();
printf("Enter a number:");scanf("%d",&n);printf("\nThe following are theprime numbers ");
6
Enter a number:
10
The following are the prime numbers
2
3
5
7
11
13
17
19
23
29
while(n!=0)
{x++;
i=2;
while(x%i!=0)
{i++;
}
if(x==i)
{ printf("\n%d",x);n--;
}
}
getch();
}
DO...WHILE LOOP IN C
Unlike
for
and
whil
e loops, which test the loop
condition at the top of the loop, the
do...while
loop in C programming language checks its
condition at the bottom of the loop.
A
do...while
loop is similar to a
while loop
,
except that a
do...while
loop is guaranteed to
execute at least one time
.
Syntax:
T he syntax of a
do...while loop
in C
programming language is:
do
{statement(s);
}
while
(
condition
);
7
C - IF STATEMENT
An
if statement
consists of a Boolean
expression followed by one or more
statements.
Syntax:
The syntax of an if statement in C
programming language is:
if
(
boolean_expression
)
{/* statement(s) will execute if the Boolean
expression is true */
}
8
C - IF...ELSE STATEMENT
An if statement can be followed by an
optional else statement, which executes
when the Boolean expression is false.
Syntax:
The syntax of an
if...else
statement in C
programming language is:
if
(
boolean_expression
)
{/* statement(s) will execute if the Boolean
expression is true */
}
else
{/* statement(s) will execute if the Boolean
expression is false */
}
9
C - SWITCH STATEMENT
A
switch
statement allows a variable to be
tested for equality against a list of values.
Each value is called a
case
, and the
variable being switched on is checked for
each
switch case
.
Syntax:
The syntax for a
switch statement in C
programming language is as follows:
switch
(expression)
{case
constant-expression :
statement(s);
break
; /* optional */
case
constant-expression :
statement(s);
break
; /* optional */
/* you can have any number of case statements */
default
: /* Optional */
statement(s);
}
10
Ex. Write a C program to read an integer and display
each of the digit of the integer in English.
#include<stdio.h>
#include<conio.h>
void main()
{int n,digit,rev=0;
clrscr();
printf("Enter a number:");scanf("%d",&n);while(n!=0)
{digit=n%10;
rev=rev*10+digit;
n=n/10;
}
while(rev!=0)
{digit=rev%10;
rev=rev/10;
switch(digit)
{ case 0:printf("Zero ");break;
case 1:printf("One ");break;
11
case 2:printf("Two ");break;
case 3:printf("Three ");break;
case 4:printf("Four ");break;
case 5:printf("Five ");break;
case 6:printf("Six ");break;
case 7:printf("Seven ");break;
case 8:printf("Eight");break;
case 9:printf("Nine ");break;
}
}
getch();
}
Enter a number:
345
Three
Four
Five
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.
12
C - Pointers
A
pointer
is a variable whose value is the address of another variable,
i.e., direct address of the memory location. Like any variable or
constant, you must declare a pointer before you can use it to store any
variable address. The general form of a pointer variable declaration is:
type
*
var-name;
Here,
type
is the pointer's base type; it must be a valid C data type
and
var-name
is the name of the pointer variable. The asterisk
*
you
used to declare a pointer is the same asterisk that you use for
multiplication. However, in this statement the asterisk is being used to
designate a variable as a pointer. Following are the valid pointer
declaration:
int *ip;
/* pointer to an integer */
double *dp;
/* pointer to a double */
float *fp;
/* pointer to a float */
char *ch
/*pointer to a character */
39
46768
Memory Address
a
Variable name
Example :ip=&a;
ip=46768;
How to use Pointers?
There are few important operations, which we will do with
the help of pointers very frequently.
(a)
we define a pointer variable
(b)
assign the address of a variable to a pointer and
(c)
finally access the value at the address available in the
pointer variable.
This is done by using unary operator
*
that returns the value
of the variable located at the address specified by its
operand. Following example makes use of these operations:
Example of Pointers
C Pointers in Detail
Pointers have many but easy concepts and they are very
important to C programming. There are following few important
pointer concepts which should be clear to a C programmer:
MCQs.
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a. Branching to a specific branch or label in program
b. Repeating a given set of statement
c. Both of above
d. None of above
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C
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#include<stdio.h>
#include<string.h>
void main()
{int i=0;
for(;i<=2;)
printf(“%d”,++i);
a. 0 1 2
b. 1 2 3
c. 0 1 2 3
d. Infinite loop
Correct Ans. D
Correct Ans. B
Correct Ans. B
MCQs.
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.
#include<stdio.h>
void main()
{int s=0;
while(s++<10)
{if(s>3 && s<10)
continue;
printf(“\n%d\t”,s);
}
}
a. 1 2 3 4 5 6 7 8 9
b. 1 2 3 10
c. 4 5 6 7 8 9 10
d. 4 5 6 7 8 9
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a. True b. False c. Depends on the condition
d. None of the above
Correct Ans. B
Correct Ans. B
MCQs.
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#include<stdio.h>
void main()
{int i,j;
for(i=1;i<=2;i++)
{for(j=1;j<=3;j++)
{printf(“Hello”);
}
printf(“\n”);
}
}
a. Hello Hello
b. Hello Hello Hello c. Hello Hello d. Hello Hello
Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello
Hello Hello Hello Hello Hello Hello
Correct Ans. B
MCQs.
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#include<stdio.h>
void main()
{int n=400;
if(n%10==0)
{printf(“Yes”);
}
else
{printf(“No”);
}
}
a. Yes
b. No
c. Compilation error
d. None of the above
Correct Ans. A
MCQs.
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void main()
{int i,j=6;
for(;i=j;j-=2)
printf(“%d”,j);
}
a. Error
b. Garbage value
c. 642
d. 6420
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void main ( )
{int a=2,b=0,c=-2;
if(b,a,c)
printf(“True”);
else
printf(“False”);
}
a. True
b. False
c. Compile time error
d. Run time error
Correct Ans. C
Correct Ans. A
End of Chapter
22
Control statements in C programming play an essential role in managing the flow of operations through iterative and conditional statements. Learn about for, while, and do-while loops, along with if-else and switch-case statements to effectively control program execution.
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Presentation Transcript
1 Developed by Mr. Sandeep G. Shukla
Control Statement In programming we need to sometimes control the flow of operation other than just the sequential statements. In this case we need the control statements. Control statements are classified into two viz. the iterative statements and conditional statement. Iterative statements are use to perform certain operation repetitively for certain number of times. In C we have three iterative statement viz. for loop, while loop and do-while loop. Conditional statements are use to perform the operations based on a particular condition i.e. if a condition is true perform one task else perform another task. In C we have two conditional statement namely if- else statement and switch-case statements. 2
FOR LOOP IN C A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. Syntax: The syntax of a for loop in C programming language is: for ( init; condition; increment ) { statement(s); } 3
Ex. Write a program in c to generate first 20 Fibonacci numbers #include<stdio.h> #include<conio.h> void main() { int a=0, b=1,c,i,n=20; printf( Fibonacci Series ); printf( \n %d \n %d ,a,b); for(i=1; i<=n-2; i++) { c=a+b; printf( \n%d ,c); a=b; b=c; } getch(); } Fibonacci Series 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 4
WHILE LOOP IN C A while loop statement language in C programming executes a target statement as long as a given condition is true. repeatedly Syntax: T he syntax of a while loop in C programming language is: while(condition) { statement(s); } 5
Ex. Write a C program to generate prime numbers between 1 to n. Enter a number: 10 The following are the prime numbers 2 3 5 7 11 13 17 19 23 29 while(n!=0) { x++; i=2; while(x%i!=0) { i++; } if(x==i) { printf("\n%d",x); n--; } } getch(); } #include<stdio.h> #include<conio.h> void main() { int i,n,x=1; clrscr(); printf("Enter a number:"); scanf("%d",&n); printf("\nThe following are the prime numbers "); 6
DO...WHILE LOOP IN C Unlike for and while loops, which test the loop condition at the top of the loop, the do...while loop in C programming language checks its condition at the bottom of the loop. A do...while loop is similar to a while loop, except that a do...while loop is guaranteed to execute at least one time . Syntax: T he syntax of a do...while loop in C programming language is: do { statement(s); }while( condition ); 7
C - IF STATEMENT An if statement consists of a Boolean expression followed by one or more statements. Syntax: The syntax of an if statement in C programming language is: if(boolean_expression) { /* statement(s) will execute if the Boolean expression is true */ } 8
C - IF...ELSE STATEMENT An if statement can be followed by an optional else statement, which executes when the Boolean expression is false. Syntax: The syntax of an if...else statement in C programming language is: if(boolean_expression) { /* statement(s) will execute if the Boolean expression is true */ } else { /* statement(s) will execute if the Boolean expression is false */ } 9
C - SWITCH STATEMENT A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each switch case. Syntax: The syntax for a switch statement in C programming language is as follows: switch(expression) { case constant-expression : statement(s); break; /* optional */ case constant-expression : statement(s); break; /* optional */ /* you can have any number of case statements */ default : /* Optional */ statement(s); } 10
Ex. Write a C program to read an integer and display each of the digit of the integer in English. #include<stdio.h> #include<conio.h> case 2:printf("Two "); break; case 3:printf("Three "); break; case 4:printf("Four "); break; case 5:printf("Five "); break; case 6:printf("Six "); break; case 7:printf("Seven "); break; case 8:printf("Eight"); break; case 9:printf("Nine "); break; } } getch(); } void main() { int n,digit,rev=0; clrscr(); printf("Enter a number:"); scanf("%d",&n); while(n!=0) { digit=n%10; rev=rev*10+digit; n=n/10; } while(rev!=0) { digit=rev%10; rev=rev/10; switch(digit) { case 0:printf("Zero "); break; case 1:printf("One "); break; Enter a number: 345 Three Four Five 11
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. Control Statement Description Terminates the loop or switch statement and transfers execution immediately following the loop or switch. break statement to the statement Causes the loop to skip the remainder of its body and immediately retest its condition prior to reiterating. continue statement Transfers control to the labeled statement. Though it is not advised to use goto statement in your program. goto statement 12
C - Pointers A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before you can use it to store any variable address. The general form of a pointer variable declaration is: type*var-name; Here, type is the pointer's base type; it must be a valid C data type and var-name is the name of the pointer variable. The asterisk * you used to declare a pointer is the same asterisk that you use for multiplication. However, in this statement the asterisk is being used to designate a variable as a pointer. Following are the valid pointer declaration: int *ip; /* pointer to an integer */ double *dp; /* pointer to a double */ float *fp; /* pointer to a float */ char *ch /*pointer to a character */ a 39 Variable name 46768 Memory Address ip=46768; Example :ip=&a;
How to use Pointers? There are few important operations, which we will do with the help of pointers very frequently. (a) we define a pointer variable (b) assign the address of a variable to a pointer and (c) finally access the value at the address available in the pointer variable. This is done by using unary operator * that returns the value of the variable located at the address specified by its operand. Following example makes use of these operations:
C Pointers in Detail Pointers have many but easy concepts and they are very important to C programming. There are following few important pointer concepts which should be clear to a C programmer: Concept Description C - Pointer arithmetic There are four arithmetic operators that can be used on pointers: ++, --, +, - C - Array of pointers You can define arrays to hold a number of pointers. C - Pointer to pointer C allows you to have pointer on a pointer and so on. Passing pointers to functions in C Passing an argument by reference or by address both enable the passed argument to be changed in the calling function by the called function. Return pointer from functions in C C allows a function to return a pointer to local variable, static variable and dynamically allocated memory as well.
MCQs. What is the final value of x when the code int x; for(x=0;x<=10;x++) a. 10 b. 9 c. 0 d. 11 Looping in the program means a. Branching to a specific branch or label in program b. Repeating a given set of statement c. Both of above Correct Ans. D d. None of above Correct Ans. B Find the output of the following C code #include<stdio.h> #include<string.h> void main() { int i=0; for(;i<=2;) printf( %d ,++i); a. 0 1 2 Correct Ans. B b. 1 2 3 c. 0 1 2 3 d. Infinite loop
MCQs. Find the output of the following code. #include<stdio.h> void main() { int s=0; while(s++<10) { } } a. 1 2 3 4 5 6 7 8 9 b. 1 2 3 10 Correct Ans. B if(s>3 && s<10) continue; printf( \n%d\t ,s); c. 4 5 6 7 8 9 10 d. 4 5 6 7 8 9 The do-while loop is an entry controlled loop a. True b. False Correct Ans. B c. Depends on the condition d. None of the above
MCQs. Find the output of the following program #include<stdio.h> void main() { int i,j; for(i=1;i<=2;i++) { } } a. Hello Hello Hello Hello Hello Hello Hello Hello Correct Ans. B for(j=1;j<=3;j++) { } printf( \n ); printf( Hello ); b. Hello Hello Hello c. Hello Hello d. Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello
MCQs. Find the output of the following program #include<stdio.h> void main() { int n=400; if(n%10==0) { } else { } } a. Yes Correct Ans. A printf( Yes ); printf( No ); b. No c. Compilation error d. None of the above
MCQs. Find the output of the following program void main() { int i,j=6; for(;i=j;j-=2) printf( %d ,j); } a. Error Find the correct output void main ( ) { int a=2,b=0,c=-2; if(b,a,c) printf( True ); else printf( False ); } a. True Correct Ans. C b. Garbage value c. 642 d. 6420 Correct Ans. A b. False c. Compile time error d. Run time error
