UNIT IV
INTRODUCTION TO C
INTRODUCTION TO C
Overview of C – Constants, Variables and Data Types – Operators and Expressions– Managing Input and Output operators – Decision Making - Branching and Looping.
2 MARKS
1. What are the different data types available in ‘C’?
There are four basic data types available in ‘C’.
1. int
2. float
3. char
4. double
2. What are Keywords?
Keywords are certain reserved words that have standard and pre-defined meaning in
‘C’. These keywords can be used only for their intended purpose.
Keywords are certain reserved words that have standard and pre-defined meaning in
‘C’. These keywords can be used only for their intended purpose.
3. What is an Operator and Operand?
An operator is a symbol that specifies an operation to be performed on operands.
Example: *, +, -, / are called arithmetic operators.
The data items that operators act upon are called operands.
Example: a+b; In this statement a and b are called operands.
An operator is a symbol that specifies an operation to be performed on operands.
Example: *, +, -, / are called arithmetic operators.
The data items that operators act upon are called operands.
Example: a+b; In this statement a and b are called operands.
4. What is Ternary operators or Conditional operators?
Ternary operators is a conditional operator with symbols ? and :
Syntax: variable = exp1 ? exp2 : exp3
If the exp1 is true variable takes value of exp2. If the exp2 is false, variable takes the
value of exp3.
5. What are the Bitwise operators available in ‘C’?
& - Bitwise AND
| - Bitwise OR
~ - One’s Complement
>> - Right shift
<< - Left shift
^ - Bitwise XOR are called bit field operators
Example: k=~j; where ~ take one’s complement of j and the result is stored in k.
6. What are the logical operators available in ‘C’?
The logical operators available in ‘C’ are
&& - Logical AND
|| - Logical OR
! - Logical NOT
7. What is the difference between Logical AND and Bitwise AND?
Logical AND (&&): Only used in conjunction with two expressions, to test more than one condition. If both the conditions are true the returns 1. If false then
return
0.
AND (&): Only used in Bitwise manipulation. It is a unary operator.
8. What is the difference between ‘=’ and ‘==’ operator?
Where = is an assignment operator and == is a relational operator.
Example:
while (i=5) is an infinite loop because it is a non zero value and while (i==5) is
true only when i=5.
9. What is type casting?
Type casting is the process of converting the value of an expression to a
particular data type.
Example:
int x,y;
c = (float) x/y; where a and y are defined as integers. Then the result of x/y is converted
into float.
10. What is conversion specification?
The conversion specifications are used to accept or display the data using the
INPUT/OUTPUT statements.
11. What is the difference between ‘a’ and “a”?
‘a’ is a character constant and “a” is a string.
12. What is the difference between if and while statement?
if while
(i) It is a conditional statement (i) It is a loop control statement
(ii) If the condition is true, it executes
some statements.
(ii) Executes the statements within the
while block if the condition is true.
(iii) If the condition is false then it stops
the execution the statements.
(iii) If the condition is false the control is
transferred to the next statement of the
loop.
13. What is the difference between while loop and do…while loop?
In the while loop the condition is first executed. If the condition is true then it
executes the body of the loop. When the condition is false it comes of the loop. In the
do…while loop first the statement is executed and then the condition is checked. The
do…while loop will execute at least one time even though the condition is false at the
very first time.
14. What is a Modulo Operator?
‘%’ is modulo operator. It gives the remainder of an integer division
Example:
a=17, b=6. Then c=%b gives 5.
15. How many bytes are occupied by the int, char, float, long int and double?
int - 2 Bytes
char - 1 Byte
float - 4 Bytes
long int - 4 Bytes
double - 8 Bytes
16. What are the types of I/O statements available in ‘C’?
There are two types of I/O statements available in ‘C’.· Formatted I/O Statements
· Unformatted I/O Statements
17. What is the difference between ++a and a++?
++a means do the increment before the operation (pre increment)
a++ means do the increment after the operation (post increment)
Example:
a=5;
x=a++; /* assign x=5*/
y=a; /*now y assigns y=6*/
x=++a; /*assigns x=7*/
18. What is a String?
String is an array of characters.
19. What is a global variable?
The global variable is a variable that is declared outside of all the functions. The
global variable is stored in memory, the default value is zero. Scope of this variable is
available in all the functions. Life as long as the program’s execution doesn’t come to an end.
20. What are the Escape Sequences present in ‘C’
\n - New Line
\b - Backspace
\t - Form feed
\’ - Single quote
\\ - Backspace
\t - Tab
\r - Carriage return
\a - Alert
\” - Double quotes
21. Construct an infinite loop using while?
while (1)
{
}
Here 1 is a non zero, value so the condition is always true. So it is an infinite loop.
22. What will happen when you access the array more than its dimension?
When you access the array more than its dimensions some garbage value is stored in the array.
23. Write the limitations of getchar( ) and sacnf( ) functions for reading strings (JAN 2009)
getchar( )
To read a single character from stdin, then getchar() is the appropriate.
scanf( )
scanf( ) allows to read more than just a single character at a time.
24. What is the difference between scanf() and gets() function?
In scanf() when there is a blank was typed, the scanf() assumes that it is an end.
gets() assumes the enter key as end. That is gets() gets a new line (\n) terminated string
of characters from the keyboard and replaces the ‘\n’ with ‘\0’.
25. What is a Structure?
Structure is a group name in which dissimilar data’s are grouped together.
26. What is meant by Control String in Input/Output Statements?
Control Statements contains the format code characters, specifies the type of
data that the user accessed within the Input/Output statements.
27. What is Union?
Union is a group name used to define dissimilar data types. The union occupies
only the maximum byte of the data type. If you declare integer and character, then the
union occupies only 2 bytes, whereas structure occupies only 3 bytes.
28. What is the output of the programs given below?
main() main()
{ {
float a; float a;
int x=6, y=4; int x=6, y=4;
a=x\y; a=(float) x\y;
printf(“Value of a=%f”, a); printf(“Value of a=%f”,a);
} }
Output: Output:
1. 1.500000
29. Declare the Structure with an example?
struct name
{
char name[10];
int age;
float salary;
} e1, e2;
30. Declare the Union with an example?
union name
{
char name[10];
int age;
float salary;
} e1, e2;
31. What is the output of the following program when, the name given with spaces?
main()
{
char name[50];
printf(“\n name\n”);
scanf(“%s, name);
printf(“%s”,name);
}
Output:
Lachi (It only accepts the data upto the spaces)
32. What is the difference between while(a) and while(!a)?
while(a) means while(a!=0)
while(!a) means while(a==0)
33. Why we don’t use the symbol ‘&’ symbol, while reading a String through scanf()?
The ‘&’ is not used in scanf() while reading string, because the character variable
itself specifies as a base address.
Example: name, &name[0] both the declarations are same.
34. What is the difference between static and auto storage classes?
Static Auto
Storage
Initial value
Scope
Life
Memory
Zero
Local to the block in which the
variables is defined
Value of the variable persists
between different function
calls.
Memory
Garbage value
Local to the block in which the
variable is defined.
The block in which the
variable is defined.
35. What is the output of the program?
main() increment()
{ {
increment(); static int i=1;
increment(); printf(“%d\n”,i)
increment();
}
i=i+1;
}
OUTPUT:
1 2
3
36. Why header files are included in ‘C’ programming?
· This section is used to include the function definitions used in the program.
· Each header file has ‘h’ extension and include using ’# include’ directive at the
beginning of a program.
37. List out some of the rules used for ‘C’ programming.
· All statements should be written in lower case letters. Upper case letters are only for
symbolic constants.
· Blank spaces may be inserted between the words. This improves the readability of statements.
· It is a free-form language; we can write statements anywhere between ‘{‘ and ‘}’.
a = b + c;
d = b*c;
(or)
a = b+c; d = b*c;
· Opening and closing braces should be balanced.
38. Define delimiters in ‘C’.
Delimiters Use
:
;
( )
[ ]
{ }
#
,
Colon
Semicolon
Parenthesis
Square Bracket
Curly Brace
Hash
Comma
Useful for label
Terminates Statement
Used in expression and functions
Used for array declaration
Scope of statement
Preprocessor directive
Variable Separator
39. What do you mean by variables in ‘C’?
· A variable is a data name used for storing a data value.
· Can be assigned different values at different times during program execution.
· Can be chosen by programmer in a meaningful way so as to reflect its function in
the program.
· Some examples
are: Sum
percent
_1
class_to
tal
40. List the difference between float and double datatype.
S No Float Double Float / Double
1
2
3
4
Occupies 4 bytes in memory
Range : 3.4 e-38 to 3.8e+38
Format Specifier: % f
Example : float a;
Occupies 8 bytes in memory
Range : 1.7 e-308 to 1.7e+308
Format Specifier: % lf
Example : double y;
There exists long double having a
range of 3.4 e -4932 to 3.4 e +4932 and
occupies 10 bytes in memory.
Example: long double k;
41. Differentiate break and continue statement
S No break continue
1
2
3
Exits from current block / loop
Control passes to next statement
Terminates the program
Loop takes next iteration
Control passes to beginning of loop
Never terminates the program
42. List the types of operators.
S No Operators Types Symbolic Representation
1
2
3
4
5
6
7
8
Arithmetic operators
Relational operators
Logical operators
Increment and Decrement operators
Assignment operators
Bitwise operators
Comma operator
Conditional operator
= , - , * , / and %
> , < , == , >=, <= and !=
&& , || and !
++ and –
= , + = , - = , * = , / = , ^ = , ; = , & =
& , | , ^ , >> , << , and ~
,
? :
43. Distinguish between while..do and do..while statement in C. (JAN 2009)
While..DO DO..while
(i) Executes the statements within the
while block if only the condition is true.
(i) Executes the statements within the
while block at least once.
(ii) The condition is checked at the
starting of the loop
(ii) The condition is checked at the end of
the loop
44. Compare switch( ) and nestedif statement.
S No switch( ) case nested if
1
2
3
4
Test for equality ie., only constant
values are applicable.
No two case statements in same
switch.
Character constants are automatically
converted to integers.
In switch( ) case statement nested if
can be used.
It can equate relational (or)
logical expressions.
Same conditions may be repeated for
a number of times.
Character constants are automatically
converted to integers.
In nested if statement switch case can
be used.
45. Distinguish Increment and Decrement operators.
S No Increment ++ Decrement --
1
2
3
4
Adds one to its operand
Equivalent x = x + 1
Either follow or precede operand
Example : ++x; x++;
Subtracts one from its operand
Equivalent x = x - 1
Either follow or precede operand
Example : --x; x--;
46. Give the syntax for the ‘for’ loop statement
for (Initialize counter; Test condition; Increment / Decrement)
{
statements;
}
· Initialization counter sets the loop to an initial value. This statement is executed
only once.
· The test condition is a relational expression that determines the number of
iterations desired or it determines when to exit from the loop. The ‘for’ loop
continues to
execute as
long as conditional test is satisfied. When condition becomes false, the control
of program
exists the body of the ‘for’ loop and executes next statement after the body of the
loop.
· The increment / decrement parameter decides how to make changes in the loop.
· The body of the loop may contain either a single statement or multiple statements.
47. What is the use of sizeof( ) operator?
· The sizeof ( ) operator gives the bytes occupied by a variable.
· No of bytes occupied varies from variable to variable depending upon its data
types.
Example:
int x,y;
printf(“%d”,sizeof(x));
Output:
2
48. What is a loop control statement?
Many tasks done with the help of a computer are repetitive in nature. Such tasks
can be done with loop control statements.
49. What are global variable in ‘C’?
· This section declares some variables that are used in more than one function. such
variable are called as global variables.
· It should be declared outside all functions.
50. Write a program to swap the values of two variables (without temporary variable).
#include <stdio.h>
#include <conio.h>
void main( )
{
int a =5; b = 10;
clrscr( );
prinf(“Before swapping a = %d b = %d “, a , b);
a = a + b;
B = a – b;
a = a – b;
prinf(“After swapping a = %d b = %d”, a,b);
getch( );
}
Output:
Before swapping a = 5 b = 10
After swapping a = 10 b = 5
51. Write short notes about main ( ) function in ’C’ program. (MAY 2009)
· Every C program must have main ( ) function.
· All functions in C, has to end with ‘( )’ parenthesis.
· It is a starting point of all ‘C’ programs.
· The program execution starts from the opening brace ‘{‘ and ends with closing brace
‘}’, within which executable part of the program exists.
12 MARKS
1. Explain in detail about ‘C’ declarations and variables.
In C, lowercase and uppercase characters are very important. All commands in C
must be lowercase. The C programs starting point is identified by the word main( ). This
informs the computer as to where the program actually starts.
The brackets that follow the keyword main indicate that there are no arguments
supplied to this program.
The two braces, { and }, signify the begin and end segments of the program. The
purpose of the statement
include <stdio.h> is to allow the use of the printf statement to provide program
output. Text to be displayed by printf() must be enclosed in double quotes. The program
has only one statement printf("Programming in C is easy.\n");
printf() is actually a function (procedure) in C that is used for printing variables
and text. Where text appears in double quotes "", it is printed without modification.
There are some exceptions however. This has to do with the \ and % characters. These
characters are modifier’s, and for the present the \ followed by the n character represents
a newline character. Thus the program prints
Programming in C is easy.
and the cursor is set to the beginning of the next line. As we shall see later on, what
follows the \ character will determine what is printed, ie, a tab, clear screen, clear line
etc. Another important thing to remember is that all C statements are terminated by a
semi-colon ;
General rules of ‘C’ language:
· program execution begins at main()
· keywords are written in lower-case
· statements are terminated with a semi-colon
· text strings are enclosed in double quotes
· C is case sensitive, use lower-case and try not to capitalize variable names
· \n means position the cursor on the beginning of the next line
· printf() can be used to display text to the screen
· The curly braces {} define the beginning and end of a program block.
BASIC STRUCTURE OF C PROGRAMS
C programs are essentially constructed in the following manner, as a number of well
defined sections.
/* HEADER SECTION */
/* Contains name, author, revision number*/
/* INCLUDE SECTION */
/* contains #include statements */
/* CONSTANTS AND TYPES SECTION */
/* contains types and #defines */
/* GLOBAL VARIABLES SECTION */
/* any global variables declared here */
/* FUNCTIONS SECTION */
/* user defined functions */
/* main() SECTION */
int main()
{
}
A Simple Program
The following program is written in the C programming language.
#include <stdio.h>
main()
{
printf(“Programming in C is easy.\n”); }
INITIALISING DATA VARIABLES AT DECLARATION TIME
In C, variables may be initialized with a value when they are declared. Consider
the following declaration, which declares an integer variable count which is initialized to
10. int count = 10;
SIMPLE ASSIGNMENT OF VALUES TO VARIABLES
The = operator is used to assign values to data variables. Consider the following
statement, which assigns the value 32 an integer variable count, and the letter A to the
character variable letter
count = 32;
letter = ‘A’
Variable Formatters
%d decimal integer
%c character
%s string or character array
%f float
%e double
HEADER FILES
Header files contain definitions of functions and variables which can be
incorporated into any C program by using the pre-processor #include statement. Standard
header files are provided with each compiler, and cover a range of areas, string handling,
mathematical, data conversion, printing and reading of variables.
To use any of the standard functions, the appropriate header file should be
included. This is done at the beginning of the C source file. For example, to use the
function printf() in a program, the line
#include <stdio.h> should be at the beginning of the source file, because the
definition for printf() is found in the file stdio.h All header files have the extension .h
and generally reside in the /include subdirectory.
#include <stdio.h>
#include “mydecls.h”
The use of angle brackets <> informs the compiler to search the compilers
include directory for the specified file. The use of the double quotes “” around the
filename inform the compiler to search in the current directory for the specified file.
2. Explain in detail about the constants, expressions and statements in ‘C’.
1. Constants: (with examples)
1. Numeric constants
a. Integer Constants
b. Real Constants
2. Character constants
a. Single character Constants
b. String Constants
2. Expressions:
An expression represents a single data item, such as number or a character.
Logical conditions that are true or false are represented by expressions.
Example: a = p – q / 3 + r * 2 - 1
3. Statements
· Assignment Statements – Definition and examples
· Null Statements – Definition and examples
· Block of statements – Definition and examples
· Expression statements – Definition and examples
· Declaration statements – Definition and examples
3. Discuss about the various data types in ‘C’. (MAY 2009)
The four basic data types are
a. INTEGER
These are whole numbers, both positive and negative. Unsigned integers
(positive values only) are supported. In addition, there are short and long integers.
The keyword used to define integers is,
int
An example of an integer value is 32. An example of declaring an integer
variable called sum is,
int sum;
sum = 20;
b. FLOATING POINT
These are numbers which contain fractional parts, both positive and negative.
The keyword used to define float variables is,
float
An example of a float value is 34.12. An example of declaring a float variable
called money is,
float money;
money = 0.12;
c. DOUBLE
These are exponentional numbers, both positive and negative. The keyword used
to define double variables is,
double
An example of a double value is 3.0E2. An example of declaring a double
variable called big is,
double big;
big = 312E+7;
d. CHARACTER
These are single characters. The keyword used to define character variables is,
char
An example of a character value is the letter A. An example of declaring a
character variable called letter is,
char letter;
letter = ‘A’;
Note the assignment of the character A to the variable letter is done by enclosing
the value in single quotes.
Example:
#include < stdio.h >
main()
{
int sum;
float money;
char letter;
double pi;
sum = 10; /* assign integer value */
money = 2.21; /* assign float value */
letter = ‘A’; /* assign character value */
pi = 2.01E6; /* assign a double value */
printf(“value of sum = %d\n”, sum );
printf(“value of money = %f\n”, money );
printf(“value of letter = %c\n”, letter );
printf(“value of pi = %e\n”, pi );
}
Sample program output
value of sum = 10
value of money = 2.210000
value of letter = A
value of pi = 2.010000e+06
4. Describe the various types of operators in ‘C’ language along with its priority.
An ex pr e s s I o n is a sequence of operators and operands that specifies
computation of a value, or that designates an object or a function, or that generates side
effects, or that performs a combination thereof.
1. ARITHMETIC OPERATORS:
The symbols of the arithmetic operators are:-
Example:
#include <stdio.h>
main()
{
int sum = 50; float modulus; modulus = sum % 10;
printf(“The %% of %d by 10 is %f\n”, sum, modulus);
}
PRE/POST INCREMENT/DECREMENT OPERATORS
PRE means do the operation first followed by any assignment operation. POST
means do the operation after any assignment operation. Consider the following
statements ++count; /* PRE Increment, means add one to count */ count++; /* P OST
Increment, means add one to count */
Example:
#include <stdio.h>
main()
{
int count = 0, loop;
loop = ++count; /* same as count = count + 1; loop = count; */
printf(“loop = %d, count = %d\n”, loop, count);
loop = count++; /* same as loop = count; count = count + 1; */
printf(“loop = %d, count = %d\n”, loop, count);
}
If the operator precedes (is on the left hand side) of the variable, the operation is
performed first, so the statement
loop = ++count;
really means increment count first, then assign the new value of count to loop.
2. THE RELATIONAL OPERATORS
These allow the comparison of two or more variables.
= = equal to
! = not equal
< less than
< = less than or equal to
> greater than
> = greater than or equal to
Example:
#include <stdio.h>
main() /* Program introduces the for statement, counts to ten */
{
int count;
for( count = 1; count <= 10; count = count + 1 )
printf(“%d “, count );
printf(“\n”);
}
3. LOGICAL OPERATORS (AND, NOT, OR, EOR)
Combining more than one condition
These allow the testing of more than one condition as part of selection
statements. The symbols are
LOGICAL AND &&
Logical and requires all conditions to evaluate as TRUE (non-zero).
LOGICAL OR ||
Logical or will be executed if any ONE of the conditions is TRUE (non-zero).
LOGICAL NOT !
logical not negates (changes from TRUE to FALSE, vsvs) a condition.
LOGICAL EOR ^
Logical eor will be excuted if either condition is TRUE, but NOT if they are all true.
Example:
The following program uses an if statement with logical AND to validate the
users input to be in the range 1-10.
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 10 à”);
scanf(“%d”, &number);
if( (number < 1 ) || (number > 10) ){
printf(“Number is outside range 1-10. Please re-enter\n”);
valid = 0;
}
else
valid = 1;
}
printf(“The number is %d\n”, number );
}
Example:
NEGATION
#include <stdio.h>
main()
{
int flag = 0;
if( ! flag ) {
printf(“The flag is not set.\n”);
flag = ! flag;
}
printf(“The value of flag is %d\n”, flag);
}
Example:
Consider where a value is to be inputted from the user, and checked for validity to be
within a certain range, lets say between the integer values 1 and 100.
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 100”);
scanf(“%d”, &number );
if( (number < 1) || (number > 100) )
printf(“Number is outside legal range\n”);
else
valid = 1;
}
printf(“Number is %d\n”, number );
}
4. THE CONDITIONAL EXPRESSION OPERATOR or TERNARY OPERATOR
This conditional expression operator takes THREE operators. The two symbols
used to denote this operator are the ? and the :. The first operand is placed before the ?,
the second operand between the ? and the :, and the third after the :. The general format
is,
condition ? expression1 : expression2.
If the result of condition is TRUE ( non-zero ), expression1 is evaluated and the
result of the evaluation becomes the result of the operation. If the condition is FALSE
(zero), then expression2 is evaluated and its result becomes the result of the operation.
An example will help,
s = ( x < 0 ) ? -1 : x * x;
If x is less than zero then s = -1
If x is greater than zero then s = x * x
Example:
#include <stdio.h>
main()
{
int input;
printf(“I will tell you if the number is positive, negative or zero!”\n”);
printf(“please enter your number now-à”);
scanf(“%d”, &input );
(input < 0) ? printf(“negative\n”) : ((input > 0) ? printf(“positive\n”) :
printf(“zero\n”));
}
5. BIT OPERATIONS
C has the advantage of direct bit manipulation and the operations available are,
Example:
/* Example program illustrating << and >> */
#include <stdio.h>
main()
{
int n1 = 10, n2 = 20, I = 0;
I = n2 << 4; /* n2 shifted left four times */
printf(“%d\n”, i);
I = n1 >> 5; /* n1 shifted right five times */
printf(“%d\n”, i);
}
Example:
/* Example program using EOR operator */
#include <stdio.h>
main()
{
int value1 = 2, value2 = 4;
value1 ^= value2;
value2 ^= value1;
value1 ^= value2;
printf(“Value1 = %d, Value2 = %d\n”, value1, value2);
}
Example:
/* Example program using AND operator */
#include <stdio.h>
main()
{
int loop;
for( loop = ‘A’; loop <= ‘Z’; loop++ )
printf(“Loop = %c, AND 0xdf = %c\n”, loop, loop & 0xdf);
}
5. Explain about the various decision making statements in ‘C’ language.
(JAN 2009/FEB2010)
1. IF STATEMENTS
DECISION MAKING
The if statements allows branching (decision making) depending upon the value
or state of variables. This allows statements to be executed or skipped, depending upon
decisions.
The basic format is,
if( expression )
program statement;
Example:
if( students < 65 )
++student_count;
In the above example, the variable student_count is incremented by one only if
the value of the integer variable students is less than 65. The following program uses an
if statement to validate the users input to be in the range 1-10.
Example:
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 10 à”);
scanf(“%d”, &number);
/* assume number is valid */
valid = 1;
if( number < 1 ) {
printf(“Number is below 1. Please re-enter\n”);
valid = 0;
}
if( number > 10 ) {
printf(“Number is above 10. Please re-enter\n”);
valid = 0;
}
}
printf(“The number is %d\n”, number );
}
2. IF ELSE
The general format for these are,
if( condition 1 )
statement1;
else if( condition 2 )
statement2;
else if( condition 3 )
www.Vidyarthiplus.com
www.Vidyarthiplus.com Page 19
statement3;
else
statement4;
The else clause allows action to be taken where the condition evaluates as false
(zero). The following program uses an if else statement to validate the users input to be
in the range 1-10.
Example:
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 10 à”);
scanf(“%d”, &number);
if( number < 1 ) {
printf(“Number is below 1. Please re-enter\n”);
valid = 0;
}
else if( number > 10 ) {
printf(“Number is above 10. Please re-enter\n”);
valid = 0;
}
else
valid = 1;
}
printf(“The number is %d\n”, number );
}
This program is slightly different from the previous example in that an else
clause is used to set the variable valid to 1. In this program, the logic should be easier to
follow.
3. NESTED IF ELSE
/* Illustates nested if else and multiple arguments to the scanf function. */
Example:
#include <stdio.h>
main()
{
int invalid_operator = 0;
char operator;
float number1, number2, result;
printf(“Enter two numbers and an operator in the format\n”);
printf(“ number1 operator number2\n”);
scanf(“%f %c %f”, &number1, &operator, &number2);
if(operator == ‘*’)
result = number1 * number2;
else if(operator == ‘/’)
result = number1 / number2;
else if(operator == ‘+’)
result = number1 + number2;
else if(operator == ‘-‘)
result = number1 – number2;
else
invalid_operator = 1;
if( invalid_operator != 1 )
printf(“%f %c %f is %f\n”, number1, operator, number2, result );
else
printf(“Invalid operator.\n”);
6. Write short notes on the following: (JAN 2009)
‘for’ loop
‘while’ loop
‘dowhile’ loop
‘Switch case ‘ (MAY 2009/FEB 2009/FEB
2010)
BRANCHING AND LOOPING
1. ITERATION, FOR LOOPS
The basic format of the for statement is,
for( start condition; continue condition; re-evaulation )
program statement;
Example:
/* sample program using a for statement */
#include <stdio.h>
main() /* Program introduces the for statement, counts to ten */
{
int count;
for( count = 1; count <= 10; count = count + 1 )
printf(“%d “, count );
printf(“\n”);
}
The program declares an integer variable count. The first part of the for
statement for (count = 1; initialized the value of count to 1.
The for loop continues with the condition count <= 10; evaluates as TRUE. As
the variable count has just been initialized to 1, this condition is TRUE and so the
program statement printf(“%d “, count ); is executed, which prints the value of count to the screen, followed by a space character.
Next, the remaining statement of the for is executed count = count + 1); which adds one to the current value of count. Control now passes back to the conditional test,
count <= 10; which evaluates as true, so the program statement printf(“%d “, count ); is executed.
Count is incremented again, the condition re-evaluated etc, until count reaches a value of
11.When this occurs, the conditional test count <= 10; evaluates as FALSE, and the for loop terminates, and program control passes to the statement printf(“\n”); which prints a newline, and then the program terminates, as there are no more statements left to
execute.
2. THE WHILE STATEMENT
The while provides a mechanism for repeating C statements whilst a condition is
true. Its format is, while( condition ) program statement;
Somewhere within the body of the while loop a statement must alter the value of
the condition to allow the loop to finish.
Example:
/* Sample program including while */
#include <stdio.h>
main()
{
int loop = 0;
while( loop <= 10 ) {
printf(“%d\n”, loop);
++loop;
}
}
The above program uses a while loop to repeat the statements
printf(“%d\n”,loop); ++loop; the value of the variable loop is less than or equalto 10.
3. THE DO WHILE STATEMENT
The do { } while statement allows a loop to continue whilst a condition evaluates as
TRUE (non-zero). The loop is executed as least once.
Example:
/* Demonstration of DO...WHILE */
#include <stdio.h>
main()
{
int value, r_digit;
printf(“Enter the 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”);
}
The above program reverses a number that is entered by the user. It does this by using the modulus % operator to extract the right most digit into the variable r_digit. The original number is then divided by 10, and the operation repeated whilst the number is
not equal to 0.
Ternary operators is a conditional operator with symbols ? and :
Syntax: variable = exp1 ? exp2 : exp3
If the exp1 is true variable takes value of exp2. If the exp2 is false, variable takes the
value of exp3.
5. What are the Bitwise operators available in ‘C’?
& - Bitwise AND
| - Bitwise OR
~ - One’s Complement
>> - Right shift
<< - Left shift
^ - Bitwise XOR are called bit field operators
Example: k=~j; where ~ take one’s complement of j and the result is stored in k.
6. What are the logical operators available in ‘C’?
The logical operators available in ‘C’ are
&& - Logical AND
|| - Logical OR
! - Logical NOT
7. What is the difference between Logical AND and Bitwise AND?
Logical AND (&&): Only used in conjunction with two expressions, to test more than one condition. If both the conditions are true the returns 1. If false then
return
0.
AND (&): Only used in Bitwise manipulation. It is a unary operator.
8. What is the difference between ‘=’ and ‘==’ operator?
Where = is an assignment operator and == is a relational operator.
Example:
while (i=5) is an infinite loop because it is a non zero value and while (i==5) is
true only when i=5.
9. What is type casting?
Type casting is the process of converting the value of an expression to a
particular data type.
Example:
int x,y;
c = (float) x/y; where a and y are defined as integers. Then the result of x/y is converted
into float.
10. What is conversion specification?
The conversion specifications are used to accept or display the data using the
INPUT/OUTPUT statements.
11. What is the difference between ‘a’ and “a”?
‘a’ is a character constant and “a” is a string.
12. What is the difference between if and while statement?
if while
(i) It is a conditional statement (i) It is a loop control statement
(ii) If the condition is true, it executes
some statements.
(ii) Executes the statements within the
while block if the condition is true.
(iii) If the condition is false then it stops
the execution the statements.
(iii) If the condition is false the control is
transferred to the next statement of the
loop.
13. What is the difference between while loop and do…while loop?
In the while loop the condition is first executed. If the condition is true then it
executes the body of the loop. When the condition is false it comes of the loop. In the
do…while loop first the statement is executed and then the condition is checked. The
do…while loop will execute at least one time even though the condition is false at the
very first time.
14. What is a Modulo Operator?
‘%’ is modulo operator. It gives the remainder of an integer division
Example:
a=17, b=6. Then c=%b gives 5.
15. How many bytes are occupied by the int, char, float, long int and double?
int - 2 Bytes
char - 1 Byte
float - 4 Bytes
long int - 4 Bytes
double - 8 Bytes
16. What are the types of I/O statements available in ‘C’?
There are two types of I/O statements available in ‘C’.· Formatted I/O Statements
· Unformatted I/O Statements
17. What is the difference between ++a and a++?
++a means do the increment before the operation (pre increment)
a++ means do the increment after the operation (post increment)
Example:
a=5;
x=a++; /* assign x=5*/
y=a; /*now y assigns y=6*/
x=++a; /*assigns x=7*/
18. What is a String?
String is an array of characters.
19. What is a global variable?
The global variable is a variable that is declared outside of all the functions. The
global variable is stored in memory, the default value is zero. Scope of this variable is
available in all the functions. Life as long as the program’s execution doesn’t come to an end.
20. What are the Escape Sequences present in ‘C’
\n - New Line
\b - Backspace
\t - Form feed
\’ - Single quote
\\ - Backspace
\t - Tab
\r - Carriage return
\a - Alert
\” - Double quotes
21. Construct an infinite loop using while?
while (1)
{
}
Here 1 is a non zero, value so the condition is always true. So it is an infinite loop.
22. What will happen when you access the array more than its dimension?
When you access the array more than its dimensions some garbage value is stored in the array.
23. Write the limitations of getchar( ) and sacnf( ) functions for reading strings (JAN 2009)
getchar( )
To read a single character from stdin, then getchar() is the appropriate.
scanf( )
scanf( ) allows to read more than just a single character at a time.
24. What is the difference between scanf() and gets() function?
In scanf() when there is a blank was typed, the scanf() assumes that it is an end.
gets() assumes the enter key as end. That is gets() gets a new line (\n) terminated string
of characters from the keyboard and replaces the ‘\n’ with ‘\0’.
25. What is a Structure?
Structure is a group name in which dissimilar data’s are grouped together.
26. What is meant by Control String in Input/Output Statements?
Control Statements contains the format code characters, specifies the type of
data that the user accessed within the Input/Output statements.
27. What is Union?
Union is a group name used to define dissimilar data types. The union occupies
only the maximum byte of the data type. If you declare integer and character, then the
union occupies only 2 bytes, whereas structure occupies only 3 bytes.
28. What is the output of the programs given below?
main() main()
{ {
float a; float a;
int x=6, y=4; int x=6, y=4;
a=x\y; a=(float) x\y;
printf(“Value of a=%f”, a); printf(“Value of a=%f”,a);
} }
Output: Output:
1. 1.500000
29. Declare the Structure with an example?
struct name
{
char name[10];
int age;
float salary;
} e1, e2;
30. Declare the Union with an example?
union name
{
char name[10];
int age;
float salary;
} e1, e2;
31. What is the output of the following program when, the name given with spaces?
main()
{
char name[50];
printf(“\n name\n”);
scanf(“%s, name);
printf(“%s”,name);
}
Output:
Lachi (It only accepts the data upto the spaces)
32. What is the difference between while(a) and while(!a)?
while(a) means while(a!=0)
while(!a) means while(a==0)
33. Why we don’t use the symbol ‘&’ symbol, while reading a String through scanf()?
The ‘&’ is not used in scanf() while reading string, because the character variable
itself specifies as a base address.
Example: name, &name[0] both the declarations are same.
34. What is the difference between static and auto storage classes?
Static Auto
Storage
Initial value
Scope
Life
Memory
Zero
Local to the block in which the
variables is defined
Value of the variable persists
between different function
calls.
Memory
Garbage value
Local to the block in which the
variable is defined.
The block in which the
variable is defined.
35. What is the output of the program?
main() increment()
{ {
increment(); static int i=1;
increment(); printf(“%d\n”,i)
increment();
}
i=i+1;
}
OUTPUT:
1 2
3
36. Why header files are included in ‘C’ programming?
· This section is used to include the function definitions used in the program.
· Each header file has ‘h’ extension and include using ’# include’ directive at the
beginning of a program.
37. List out some of the rules used for ‘C’ programming.
· All statements should be written in lower case letters. Upper case letters are only for
symbolic constants.
· Blank spaces may be inserted between the words. This improves the readability of statements.
· It is a free-form language; we can write statements anywhere between ‘{‘ and ‘}’.
a = b + c;
d = b*c;
(or)
a = b+c; d = b*c;
· Opening and closing braces should be balanced.
38. Define delimiters in ‘C’.
Delimiters Use
:
;
( )
[ ]
{ }
#
,
Colon
Semicolon
Parenthesis
Square Bracket
Curly Brace
Hash
Comma
Useful for label
Terminates Statement
Used in expression and functions
Used for array declaration
Scope of statement
Preprocessor directive
Variable Separator
39. What do you mean by variables in ‘C’?
· A variable is a data name used for storing a data value.
· Can be assigned different values at different times during program execution.
· Can be chosen by programmer in a meaningful way so as to reflect its function in
the program.
· Some examples
are: Sum
percent
_1
class_to
tal
40. List the difference between float and double datatype.
S No Float Double Float / Double
1
2
3
4
Occupies 4 bytes in memory
Range : 3.4 e-38 to 3.8e+38
Format Specifier: % f
Example : float a;
Occupies 8 bytes in memory
Range : 1.7 e-308 to 1.7e+308
Format Specifier: % lf
Example : double y;
There exists long double having a
range of 3.4 e -4932 to 3.4 e +4932 and
occupies 10 bytes in memory.
Example: long double k;
41. Differentiate break and continue statement
S No break continue
1
2
3
Exits from current block / loop
Control passes to next statement
Terminates the program
Loop takes next iteration
Control passes to beginning of loop
Never terminates the program
42. List the types of operators.
S No Operators Types Symbolic Representation
1
2
3
4
5
6
7
8
Arithmetic operators
Relational operators
Logical operators
Increment and Decrement operators
Assignment operators
Bitwise operators
Comma operator
Conditional operator
= , - , * , / and %
> , < , == , >=, <= and !=
&& , || and !
++ and –
= , + = , - = , * = , / = , ^ = , ; = , & =
& , | , ^ , >> , << , and ~
,
? :
43. Distinguish between while..do and do..while statement in C. (JAN 2009)
While..DO DO..while
(i) Executes the statements within the
while block if only the condition is true.
(i) Executes the statements within the
while block at least once.
(ii) The condition is checked at the
starting of the loop
(ii) The condition is checked at the end of
the loop
44. Compare switch( ) and nestedif statement.
S No switch( ) case nested if
1
2
3
4
Test for equality ie., only constant
values are applicable.
No two case statements in same
switch.
Character constants are automatically
converted to integers.
In switch( ) case statement nested if
can be used.
It can equate relational (or)
logical expressions.
Same conditions may be repeated for
a number of times.
Character constants are automatically
converted to integers.
In nested if statement switch case can
be used.
45. Distinguish Increment and Decrement operators.
S No Increment ++ Decrement --
1
2
3
4
Adds one to its operand
Equivalent x = x + 1
Either follow or precede operand
Example : ++x; x++;
Subtracts one from its operand
Equivalent x = x - 1
Either follow or precede operand
Example : --x; x--;
46. Give the syntax for the ‘for’ loop statement
for (Initialize counter; Test condition; Increment / Decrement)
{
statements;
}
· Initialization counter sets the loop to an initial value. This statement is executed
only once.
· The test condition is a relational expression that determines the number of
iterations desired or it determines when to exit from the loop. The ‘for’ loop
continues to
execute as
long as conditional test is satisfied. When condition becomes false, the control
of program
exists the body of the ‘for’ loop and executes next statement after the body of the
loop.
· The increment / decrement parameter decides how to make changes in the loop.
· The body of the loop may contain either a single statement or multiple statements.
47. What is the use of sizeof( ) operator?
· The sizeof ( ) operator gives the bytes occupied by a variable.
· No of bytes occupied varies from variable to variable depending upon its data
types.
Example:
int x,y;
printf(“%d”,sizeof(x));
Output:
2
48. What is a loop control statement?
Many tasks done with the help of a computer are repetitive in nature. Such tasks
can be done with loop control statements.
49. What are global variable in ‘C’?
· This section declares some variables that are used in more than one function. such
variable are called as global variables.
· It should be declared outside all functions.
50. Write a program to swap the values of two variables (without temporary variable).
#include <stdio.h>
#include <conio.h>
void main( )
{
int a =5; b = 10;
clrscr( );
prinf(“Before swapping a = %d b = %d “, a , b);
a = a + b;
B = a – b;
a = a – b;
prinf(“After swapping a = %d b = %d”, a,b);
getch( );
}
Output:
Before swapping a = 5 b = 10
After swapping a = 10 b = 5
51. Write short notes about main ( ) function in ’C’ program. (MAY 2009)
· Every C program must have main ( ) function.
· All functions in C, has to end with ‘( )’ parenthesis.
· It is a starting point of all ‘C’ programs.
· The program execution starts from the opening brace ‘{‘ and ends with closing brace
‘}’, within which executable part of the program exists.
12 MARKS
1. Explain in detail about ‘C’ declarations and variables.
In C, lowercase and uppercase characters are very important. All commands in C
must be lowercase. The C programs starting point is identified by the word main( ). This
informs the computer as to where the program actually starts.
The brackets that follow the keyword main indicate that there are no arguments
supplied to this program.
The two braces, { and }, signify the begin and end segments of the program. The
purpose of the statement
include <stdio.h> is to allow the use of the printf statement to provide program
output. Text to be displayed by printf() must be enclosed in double quotes. The program
has only one statement printf("Programming in C is easy.\n");
printf() is actually a function (procedure) in C that is used for printing variables
and text. Where text appears in double quotes "", it is printed without modification.
There are some exceptions however. This has to do with the \ and % characters. These
characters are modifier’s, and for the present the \ followed by the n character represents
a newline character. Thus the program prints
Programming in C is easy.
and the cursor is set to the beginning of the next line. As we shall see later on, what
follows the \ character will determine what is printed, ie, a tab, clear screen, clear line
etc. Another important thing to remember is that all C statements are terminated by a
semi-colon ;
General rules of ‘C’ language:
· program execution begins at main()
· keywords are written in lower-case
· statements are terminated with a semi-colon
· text strings are enclosed in double quotes
· C is case sensitive, use lower-case and try not to capitalize variable names
· \n means position the cursor on the beginning of the next line
· printf() can be used to display text to the screen
· The curly braces {} define the beginning and end of a program block.
BASIC STRUCTURE OF C PROGRAMS
C programs are essentially constructed in the following manner, as a number of well
defined sections.
/* HEADER SECTION */
/* Contains name, author, revision number*/
/* INCLUDE SECTION */
/* contains #include statements */
/* CONSTANTS AND TYPES SECTION */
/* contains types and #defines */
/* GLOBAL VARIABLES SECTION */
/* any global variables declared here */
/* FUNCTIONS SECTION */
/* user defined functions */
/* main() SECTION */
int main()
{
}
A Simple Program
The following program is written in the C programming language.
#include <stdio.h>
main()
{
printf(“Programming in C is easy.\n”); }
INITIALISING DATA VARIABLES AT DECLARATION TIME
In C, variables may be initialized with a value when they are declared. Consider
the following declaration, which declares an integer variable count which is initialized to
10. int count = 10;
SIMPLE ASSIGNMENT OF VALUES TO VARIABLES
The = operator is used to assign values to data variables. Consider the following
statement, which assigns the value 32 an integer variable count, and the letter A to the
character variable letter
count = 32;
letter = ‘A’
Variable Formatters
%d decimal integer
%c character
%s string or character array
%f float
%e double
HEADER FILES
Header files contain definitions of functions and variables which can be
incorporated into any C program by using the pre-processor #include statement. Standard
header files are provided with each compiler, and cover a range of areas, string handling,
mathematical, data conversion, printing and reading of variables.
To use any of the standard functions, the appropriate header file should be
included. This is done at the beginning of the C source file. For example, to use the
function printf() in a program, the line
#include <stdio.h> should be at the beginning of the source file, because the
definition for printf() is found in the file stdio.h All header files have the extension .h
and generally reside in the /include subdirectory.
#include <stdio.h>
#include “mydecls.h”
The use of angle brackets <> informs the compiler to search the compilers
include directory for the specified file. The use of the double quotes “” around the
filename inform the compiler to search in the current directory for the specified file.
2. Explain in detail about the constants, expressions and statements in ‘C’.
1. Constants: (with examples)
1. Numeric constants
a. Integer Constants
b. Real Constants
2. Character constants
a. Single character Constants
b. String Constants
2. Expressions:
An expression represents a single data item, such as number or a character.
Logical conditions that are true or false are represented by expressions.
Example: a = p – q / 3 + r * 2 - 1
3. Statements
· Assignment Statements – Definition and examples
· Null Statements – Definition and examples
· Block of statements – Definition and examples
· Expression statements – Definition and examples
· Declaration statements – Definition and examples
3. Discuss about the various data types in ‘C’. (MAY 2009)
The four basic data types are
a. INTEGER
These are whole numbers, both positive and negative. Unsigned integers
(positive values only) are supported. In addition, there are short and long integers.
The keyword used to define integers is,
int
An example of an integer value is 32. An example of declaring an integer
variable called sum is,
int sum;
sum = 20;
b. FLOATING POINT
These are numbers which contain fractional parts, both positive and negative.
The keyword used to define float variables is,
float
An example of a float value is 34.12. An example of declaring a float variable
called money is,
float money;
money = 0.12;
c. DOUBLE
These are exponentional numbers, both positive and negative. The keyword used
to define double variables is,
double
An example of a double value is 3.0E2. An example of declaring a double
variable called big is,
double big;
big = 312E+7;
d. CHARACTER
These are single characters. The keyword used to define character variables is,
char
An example of a character value is the letter A. An example of declaring a
character variable called letter is,
char letter;
letter = ‘A’;
Note the assignment of the character A to the variable letter is done by enclosing
the value in single quotes.
Example:
#include < stdio.h >
main()
{
int sum;
float money;
char letter;
double pi;
sum = 10; /* assign integer value */
money = 2.21; /* assign float value */
letter = ‘A’; /* assign character value */
pi = 2.01E6; /* assign a double value */
printf(“value of sum = %d\n”, sum );
printf(“value of money = %f\n”, money );
printf(“value of letter = %c\n”, letter );
printf(“value of pi = %e\n”, pi );
}
Sample program output
value of sum = 10
value of money = 2.210000
value of letter = A
value of pi = 2.010000e+06
4. Describe the various types of operators in ‘C’ language along with its priority.
An ex pr e s s I o n is a sequence of operators and operands that specifies
computation of a value, or that designates an object or a function, or that generates side
effects, or that performs a combination thereof.
1. ARITHMETIC OPERATORS:
The symbols of the arithmetic operators are:-
Example:
#include <stdio.h>
main()
{
int sum = 50; float modulus; modulus = sum % 10;
printf(“The %% of %d by 10 is %f\n”, sum, modulus);
}
PRE/POST INCREMENT/DECREMENT OPERATORS
PRE means do the operation first followed by any assignment operation. POST
means do the operation after any assignment operation. Consider the following
statements ++count; /* PRE Increment, means add one to count */ count++; /* P OST
Increment, means add one to count */
Example:
#include <stdio.h>
main()
{
int count = 0, loop;
loop = ++count; /* same as count = count + 1; loop = count; */
printf(“loop = %d, count = %d\n”, loop, count);
loop = count++; /* same as loop = count; count = count + 1; */
printf(“loop = %d, count = %d\n”, loop, count);
}
If the operator precedes (is on the left hand side) of the variable, the operation is
performed first, so the statement
loop = ++count;
really means increment count first, then assign the new value of count to loop.
2. THE RELATIONAL OPERATORS
These allow the comparison of two or more variables.
= = equal to
! = not equal
< less than
< = less than or equal to
> greater than
> = greater than or equal to
Example:
#include <stdio.h>
main() /* Program introduces the for statement, counts to ten */
{
int count;
for( count = 1; count <= 10; count = count + 1 )
printf(“%d “, count );
printf(“\n”);
}
3. LOGICAL OPERATORS (AND, NOT, OR, EOR)
Combining more than one condition
These allow the testing of more than one condition as part of selection
statements. The symbols are
LOGICAL AND &&
Logical and requires all conditions to evaluate as TRUE (non-zero).
LOGICAL OR ||
Logical or will be executed if any ONE of the conditions is TRUE (non-zero).
LOGICAL NOT !
logical not negates (changes from TRUE to FALSE, vsvs) a condition.
LOGICAL EOR ^
Logical eor will be excuted if either condition is TRUE, but NOT if they are all true.
Example:
The following program uses an if statement with logical AND to validate the
users input to be in the range 1-10.
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 10 à”);
scanf(“%d”, &number);
if( (number < 1 ) || (number > 10) ){
printf(“Number is outside range 1-10. Please re-enter\n”);
valid = 0;
}
else
valid = 1;
}
printf(“The number is %d\n”, number );
}
Example:
NEGATION
#include <stdio.h>
main()
{
int flag = 0;
if( ! flag ) {
printf(“The flag is not set.\n”);
flag = ! flag;
}
printf(“The value of flag is %d\n”, flag);
}
Example:
Consider where a value is to be inputted from the user, and checked for validity to be
within a certain range, lets say between the integer values 1 and 100.
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 100”);
scanf(“%d”, &number );
if( (number < 1) || (number > 100) )
printf(“Number is outside legal range\n”);
else
valid = 1;
}
printf(“Number is %d\n”, number );
}
4. THE CONDITIONAL EXPRESSION OPERATOR or TERNARY OPERATOR
This conditional expression operator takes THREE operators. The two symbols
used to denote this operator are the ? and the :. The first operand is placed before the ?,
the second operand between the ? and the :, and the third after the :. The general format
is,
condition ? expression1 : expression2.
If the result of condition is TRUE ( non-zero ), expression1 is evaluated and the
result of the evaluation becomes the result of the operation. If the condition is FALSE
(zero), then expression2 is evaluated and its result becomes the result of the operation.
An example will help,
s = ( x < 0 ) ? -1 : x * x;
If x is less than zero then s = -1
If x is greater than zero then s = x * x
Example:
#include <stdio.h>
main()
{
int input;
printf(“I will tell you if the number is positive, negative or zero!”\n”);
printf(“please enter your number now-à”);
scanf(“%d”, &input );
(input < 0) ? printf(“negative\n”) : ((input > 0) ? printf(“positive\n”) :
printf(“zero\n”));
}
5. BIT OPERATIONS
C has the advantage of direct bit manipulation and the operations available are,
Example:
/* Example program illustrating << and >> */
#include <stdio.h>
main()
{
int n1 = 10, n2 = 20, I = 0;
I = n2 << 4; /* n2 shifted left four times */
printf(“%d\n”, i);
I = n1 >> 5; /* n1 shifted right five times */
printf(“%d\n”, i);
}
Example:
/* Example program using EOR operator */
#include <stdio.h>
main()
{
int value1 = 2, value2 = 4;
value1 ^= value2;
value2 ^= value1;
value1 ^= value2;
printf(“Value1 = %d, Value2 = %d\n”, value1, value2);
}
Example:
/* Example program using AND operator */
#include <stdio.h>
main()
{
int loop;
for( loop = ‘A’; loop <= ‘Z’; loop++ )
printf(“Loop = %c, AND 0xdf = %c\n”, loop, loop & 0xdf);
}
5. Explain about the various decision making statements in ‘C’ language.
(JAN 2009/FEB2010)
1. IF STATEMENTS
DECISION MAKING
The if statements allows branching (decision making) depending upon the value
or state of variables. This allows statements to be executed or skipped, depending upon
decisions.
The basic format is,
if( expression )
program statement;
Example:
if( students < 65 )
++student_count;
In the above example, the variable student_count is incremented by one only if
the value of the integer variable students is less than 65. The following program uses an
if statement to validate the users input to be in the range 1-10.
Example:
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 10 à”);
scanf(“%d”, &number);
/* assume number is valid */
valid = 1;
if( number < 1 ) {
printf(“Number is below 1. Please re-enter\n”);
valid = 0;
}
if( number > 10 ) {
printf(“Number is above 10. Please re-enter\n”);
valid = 0;
}
}
printf(“The number is %d\n”, number );
}
2. IF ELSE
The general format for these are,
if( condition 1 )
statement1;
else if( condition 2 )
statement2;
else if( condition 3 )
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www.Vidyarthiplus.com Page 19
statement3;
else
statement4;
The else clause allows action to be taken where the condition evaluates as false
(zero). The following program uses an if else statement to validate the users input to be
in the range 1-10.
Example:
#include <stdio.h>
main()
{
int number;
int valid = 0;
while( valid == 0 ) {
printf(“Enter a number between 1 and 10 à”);
scanf(“%d”, &number);
if( number < 1 ) {
printf(“Number is below 1. Please re-enter\n”);
valid = 0;
}
else if( number > 10 ) {
printf(“Number is above 10. Please re-enter\n”);
valid = 0;
}
else
valid = 1;
}
printf(“The number is %d\n”, number );
}
This program is slightly different from the previous example in that an else
clause is used to set the variable valid to 1. In this program, the logic should be easier to
follow.
3. NESTED IF ELSE
/* Illustates nested if else and multiple arguments to the scanf function. */
Example:
#include <stdio.h>
main()
{
int invalid_operator = 0;
char operator;
float number1, number2, result;
printf(“Enter two numbers and an operator in the format\n”);
printf(“ number1 operator number2\n”);
scanf(“%f %c %f”, &number1, &operator, &number2);
if(operator == ‘*’)
result = number1 * number2;
else if(operator == ‘/’)
result = number1 / number2;
else if(operator == ‘+’)
result = number1 + number2;
else if(operator == ‘-‘)
result = number1 – number2;
else
invalid_operator = 1;
if( invalid_operator != 1 )
printf(“%f %c %f is %f\n”, number1, operator, number2, result );
else
printf(“Invalid operator.\n”);
6. Write short notes on the following: (JAN 2009)
‘for’ loop
‘while’ loop
‘dowhile’ loop
‘Switch case ‘ (MAY 2009/FEB 2009/FEB
2010)
BRANCHING AND LOOPING
1. ITERATION, FOR LOOPS
The basic format of the for statement is,
for( start condition; continue condition; re-evaulation )
program statement;
Example:
/* sample program using a for statement */
#include <stdio.h>
main() /* Program introduces the for statement, counts to ten */
{
int count;
for( count = 1; count <= 10; count = count + 1 )
printf(“%d “, count );
printf(“\n”);
}
The program declares an integer variable count. The first part of the for
statement for (count = 1; initialized the value of count to 1.
The for loop continues with the condition count <= 10; evaluates as TRUE. As
the variable count has just been initialized to 1, this condition is TRUE and so the
program statement printf(“%d “, count ); is executed, which prints the value of count to the screen, followed by a space character.
Next, the remaining statement of the for is executed count = count + 1); which adds one to the current value of count. Control now passes back to the conditional test,
count <= 10; which evaluates as true, so the program statement printf(“%d “, count ); is executed.
Count is incremented again, the condition re-evaluated etc, until count reaches a value of
11.When this occurs, the conditional test count <= 10; evaluates as FALSE, and the for loop terminates, and program control passes to the statement printf(“\n”); which prints a newline, and then the program terminates, as there are no more statements left to
execute.
2. THE WHILE STATEMENT
The while provides a mechanism for repeating C statements whilst a condition is
true. Its format is, while( condition ) program statement;
Somewhere within the body of the while loop a statement must alter the value of
the condition to allow the loop to finish.
Example:
/* Sample program including while */
#include <stdio.h>
main()
{
int loop = 0;
while( loop <= 10 ) {
printf(“%d\n”, loop);
++loop;
}
}
The above program uses a while loop to repeat the statements
printf(“%d\n”,loop); ++loop; the value of the variable loop is less than or equalto 10.
3. THE DO WHILE STATEMENT
The do { } while statement allows a loop to continue whilst a condition evaluates as
TRUE (non-zero). The loop is executed as least once.
Example:
/* Demonstration of DO...WHILE */
#include <stdio.h>
main()
{
int value, r_digit;
printf(“Enter the 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”);
}
The above program reverses a number that is entered by the user. It does this by using the modulus % operator to extract the right most digit into the variable r_digit. The original number is then divided by 10, and the operation repeated whilst the number is
not equal to 0.
4. SWITCH CASE:
The switch case statement is a better way of writing a program when a series of if elses occurs.
The general format for this is,
switch ( expression ) {
case value1:
program statement;
program statement;
......
break;
case valuen:
program statement;
.......
break;
default:
.......
.......
break;
}
The keyword break must be included at the end of each case statement. The default clause is optional, and is executed if the cases are not met. The right brace at the
end signifies the end of the case selections.
Example:
#include <stdio.h>
main()
{
int menu, numb1, numb2, total;
printf(“enter in two numbers à”);
scanf(“%d %d”, &numb1, &numb2 );
printf(“enter in choice\n”);
printf(“1=addition\n”);
printf(“2=subtraction\n”);
scanf(“%d”, &menu );
switch( menu ) {
case 1: total = numb1 + numb2; break;
case 2: total = numb1 – numb2; break;
default: printf(“Invalid option selected\n”);
}
if( menu == 1 )
printf(“%d plus %d is %d\n”, numb1, numb2, total );
else if( menu == 2 )
printf(“%d minus %d is %d\n”, numb1, numb2, total );
}
The above program uses a switch statement to validate and select upon the users
input choice, simulating a simple menu of choices.
The switch case statement is a better way of writing a program when a series of if elses occurs.
The general format for this is,
switch ( expression ) {
case value1:
program statement;
program statement;
......
break;
case valuen:
program statement;
.......
break;
default:
.......
.......
break;
}
The keyword break must be included at the end of each case statement. The default clause is optional, and is executed if the cases are not met. The right brace at the
end signifies the end of the case selections.
Example:
#include <stdio.h>
main()
{
int menu, numb1, numb2, total;
printf(“enter in two numbers à”);
scanf(“%d %d”, &numb1, &numb2 );
printf(“enter in choice\n”);
printf(“1=addition\n”);
printf(“2=subtraction\n”);
scanf(“%d”, &menu );
switch( menu ) {
case 1: total = numb1 + numb2; break;
case 2: total = numb1 – numb2; break;
default: printf(“Invalid option selected\n”);
}
if( menu == 1 )
printf(“%d plus %d is %d\n”, numb1, numb2, total );
else if( menu == 2 )
printf(“%d minus %d is %d\n”, numb1, numb2, total );
}
The above program uses a switch statement to validate and select upon the users
input choice, simulating a simple menu of choices.
7. Explain briefly about the input and output function in ‘C’. (MAY 2009/FEB 2009)
1 printf ():
MANAGING INPUT AND OUTPUT OPERATORS
printf() is actually a function (procedure) in C that is used for printing variables and text. Where text appears in double quotes “”, it is printed without modification.
There are some exceptions however.
This has to do with the \ and % characters. These characters are modifiers, and for the present the \ followed by the n character represents a newline character.
Example:
#include <stdio.h>
main()
{
printf(“Programming in C is easy.\n”);
printf(“And so is Pascal.\n”);
}
@ Programming in C is easy.
And so is Pascal.
FORMATTERS for printf are,
Cursor Control Formatters
\n newline
\t tab
\r carriage return
\f form feed
\v vertical tab
1 printf ():
MANAGING INPUT AND OUTPUT OPERATORS
printf() is actually a function (procedure) in C that is used for printing variables and text. Where text appears in double quotes “”, it is printed without modification.
There are some exceptions however.
This has to do with the \ and % characters. These characters are modifiers, and for the present the \ followed by the n character represents a newline character.
Example:
#include <stdio.h>
main()
{
printf(“Programming in C is easy.\n”);
printf(“And so is Pascal.\n”);
}
@ Programming in C is easy.
And so is Pascal.
FORMATTERS for printf are,
Cursor Control Formatters
\n newline
\t tab
\r carriage return
\f form feed
\v vertical tab
2. Scanf ():
Scanf () is a function in C which allows the programmer to accept input from a keyboard.
Example:
#include <stdio.h>
main() /* program which introduces keyboard input */
{
int number;
printf(“Type in a number \n”);
scanf(“%d”, &number);
printf(“The number you typed was %d\n”, number);
}
FORMATTERS FOR scanf()
The following characters, after the % character, in a scanf argument, have the
following effect.
D read a decimal integer
o read an octal value
x read a hexadecimal value
h read a short integer
l read a long integer
f read a float value
e read a double value
c read a single character
s read a sequence of characters
[...] Read a character string. The characters inside the brackets
Scanf () is a function in C which allows the programmer to accept input from a keyboard.
Example:
#include <stdio.h>
main() /* program which introduces keyboard input */
{
int number;
printf(“Type in a number \n”);
scanf(“%d”, &number);
printf(“The number you typed was %d\n”, number);
}
FORMATTERS FOR scanf()
The following characters, after the % character, in a scanf argument, have the
following effect.
D read a decimal integer
o read an octal value
x read a hexadecimal value
h read a short integer
l read a long integer
f read a float value
e read a double value
c read a single character
s read a sequence of characters
[...] Read a character string. The characters inside the brackets
3. ACCEPTING SINGLE CHARACTERS FROM THE KEYBOARD
Getchar, Putchar
getchar() gets a single character from the keyboard, and putchar() writes a single
character from the keyboard.
Example:
The following program illustrates this,
#include <stdio.h>
main()
{
int i;
int ch;
for( i = 1; i<= 5; ++i ) {
ch = getchar();
putchar(ch);
}
}
The program reads five characters (one for each iteration of the for loop) from the keyboard. Note that getchar() gets a single character from the keyboard, and putchar() writes a single character (in this case, ch) to the console screen.
8. (a) Describe in detail about type conversions in ‘C’ with example.
(b) Define delimiters. List them. Give an example program using various delimiters.
Getchar, Putchar
getchar() gets a single character from the keyboard, and putchar() writes a single
character from the keyboard.
Example:
The following program illustrates this,
#include <stdio.h>
main()
{
int i;
int ch;
for( i = 1; i<= 5; ++i ) {
ch = getchar();
putchar(ch);
}
}
The program reads five characters (one for each iteration of the for loop) from the keyboard. Note that getchar() gets a single character from the keyboard, and putchar() writes a single character (in this case, ch) to the console screen.
8. (a) Describe in detail about type conversions in ‘C’ with example.
(b) Define delimiters. List them. Give an example program using various delimiters.
9. Explain the following:
· Keywords
· Identifiers
· C character set
· Constant and Volatile variables.
· Keywords
· Identifiers
· C character set
· Constant and Volatile variables.
10. Explain the following:
· break statement with example program
· continue statement with example program
· goto statement with example program
*************
· break statement with example program
· continue statement with example program
· goto statement with example program
*************
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