What is C?

1
UNIT II
2

• Input Output Statements
• In C language, two types of Input/Output
  statements are available and all input and output
  operations are carried out through function
  calls. These function collectively known as
  standard I/O library.
• 1.unformated Input/Output statements
• 2.Formated Input/Output statements
• Unformatted Input/Output statemetns
• These statements are used to Input/Output a
  single/group of characters from/to the
  input/output devices.Here the user cannot specify
  the type of data i.e, going to be input/output.

3
Input/output Functions
Unformatted Input/output statements Unformatted Input/output statements
Input Output
getc() getchar() gets() putc() putchar() puts()
Formated Input/output statements Formated Input/output statements
Input Output
scanf() fscanf() printf() Fprintf()
4

• The following are the unformatted Input/output
  statements available in c
• Single Character Input-getchar() function
• A single character can be given to the computer
  using C input library function getchar().
• The getchar() function is written in standard
  I/O library. It reads a single character from a
  standard input device.

Input Output
getchar() getc() gets() putchar() putc() puts()
Synatx char variablegetchar()
Description chardatatype VariableAny vlid c variable
Example char x Xgetchar()
5

• Example
• / Program for testing character type /
• includeltstdio.hgt
• void main()
• char ch
• printf(Enter any character/digit)
• chgetchar()
• if(isalpha(ch)gt0)
• printf(It is a alphabet)
• else if(isdigit(ch)gt0)
• printf(It a digit)
• else
• printf(It is alphanumeric)

6

• Single Character Input-putchar() function
• The putchar() function is used to display one
  character at a time on the standard output
  device.
• Example
• includeltstdio.hgt
• void main()
• char ch
• printf(Enter any alphabet either in Lowercase
  or Uppercase)
• chgetchar()
• if(islower(ch))
• putchar(toupper(ch))
• else
• putchar(tolower(ch))

Syntax putchar(character variable)
Description Character variable is the valid c variable of the type of char data type.
Example char x putchar(x)
7

• getc() function
• This is used to accept a single character
  from the standard input to a character variable.
• Syntax
• putc() function
• This is used to display a single character in a
  character variable to standard output device.

Syntax character variablegetc()
Description Character variable is the valid c variable of the type of char data type
Example char c cgetc()
Syntax putc(character variable)
Description Character variable is the valid c variable of the data type.
Example char c putc(c)
8

• gets() and puts() function
• The gets() function is used to read the
  string(string is a group of characters) from the
  standard input device(keyboard).
• The putc() function is used to display/write
  the string to the standard output
  device(Monitor).

Syntax gets(char type of array variable)
Description Valid c variable declared as one dimension char type.
Example gets(s)
Syntax puts(char type of array variable)
Description Valid c variable declared as one dimension char type.
Example Puts(s)
9

• Example
• includeltstdio.hgt
• void main()
• char name40
• puts(Enter Name)
• gets(name)
• puts(Print Name)
• put(name)

10
Formated Data Input Output FunctionsFormated
Input/output that has been arranged in a
particular formatExample LAK 397

• The following are the formatted Input/Output
  statements
• scanf() Function
• The scanf() function is used to read
  information from the standard input
  device(keyboard),scanf() function starts with a
  string argument and may contain additional
  arguments.

Input Output
scanf() printf()
fscanf() fprintf()
Syntax Scanf(control string,var1,var2,.varn)
Description The Control String consists f character groups.
Example scanf(d,n)
11

• Control String The below table illustrates code
  formats(control strings) in Input/Output
  statements.
• Each variable name(argument) must be proceeded
  by an ampersand().The symbol address of
  the variable.

Format Code Meaning
c To read a single character
d To read a decimal number
e To read a floating point value
f To read a floating point value
g To read a floating point value
o To read an octal value
x To read hexadecimal value
s To read a sting
u To read an unsigned integer
12

• Rules for writing scanf() function
• 1.The control string must be preceded with()
  sign and must be within quotations.
• 2.If there is a number of input data items, items
  must be separated by commas and must be preceded
  with() sign.
• 3.The control string and the variables going to
  input should match with each other.
• 4.It must have termination with semicolon.
• 5.The scanf() reads the data values until the
  blank space n numeric input or maximum number of
  character have been read, or error is detected.

13

• printf() Function The function is used to
  output any combination of data. It is similar to
  the input function scanf().
• Rules for writing printf() function
• a)Place appropriate headings in the output.
• b)The variable must be separated by commas, and
  need not be preceded with sign.
• c)The control string ad the variables must match
  in their order.
• d)The control string must be in quotations and
  there we can also use any other text to print
  with data.
• e)Print special messages wherever required in
  output.

Syntax printf(control string,var1,var2,varn)
Description Control string is one of the following a)Format code character b)Execution character c)Characters/String will be displayed
Example printf(Result isd,n) printf(f,f) Printf(s,s)
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CONTROL STRUCTURE

• When a program is given to a computer, it carries
  out the instructions in the sequential order.
  This is called the normal flow of control.
• The C statements used to change the control flow
  are called thee C control statements or control
  structures.
• The following control structures
• Logical IF structure
• IF-ELSE structure
• Nested ifelse statement
• Ifelse ladder
• Unconditional GOTO statement
• Switch structure

15

• Logical IF Structure
• The logical IF statement is a decision making
  statement. It is used to control the flow of
  execution of the statements and also used to test
  logically the condition is true or false.
• Syntax
• if(condition is true)
• true statements
• Where
• condition-gtis a logical condition
• statement-gtexecutable statement

16
Condition
F
T
True Statement
17

• Properties of an If statement
• 1.If the condition is true, then the simple or
  compound condition statements are executed.
• 2.If the condition is false, it does not do any
  thing.
• 3.The condition is given in parenthesis and must
  be evaluated as true(non-zero value) or
  false(zero value)
• 4.If a compound structure is provided, it must be
  enclosed in opening and closing braces.
• Example
• includeltstdio.hgt
• includeltconio.hgt
• void main()
• int x10,y
• clrscr()
• if(x10)
• printf("TRUE")
• getch()

18

• If-else statement
• It is used to control the flow of execution and
  also used to carry out the logical test then
  pickup one of the two actions depending on the
  logical test.
• Syntax
• if(condition)
• True statement
• else
• False statement

19
Condition
T
F
True Statement
False Statement
20

• includeltstdio.hgt
• includeltconio.hgt
• void main()
• int num,rem
• clrscr()
• printf(Enter your number)
• scanf(i,num)
• remnum2
• if(rem0)
• printf(The entered number is even.)
• else
• printf(The entered number is odd.)

21
Nested ifelse statement When series of ifelse
statements are occurred in a program entire
ifelse statement in another ifelse statement
called nesting, the statement is called nested
if.
Condition1
F

• if(condition 1)
• if(condition 2)
• True statement2
• else
• False statement2
• else
• False statement1

False statement 1
T
Condition2
T
F
True statement2
False statement2
22
ifelse Ladder Nested if statements can become
quite complex. If there are more than three
alternatives indentation.

• Syntax
• if(condition 1)
• statement 1
• else if(condition 2)
• statement 2
• else if(condition
  3)
• statement
  3
• else
• 
  default-statements

23
T
F
Condition 1
Condition 2
T
F
Statement 1
F
Condition 2
T
Statement 2
Statement 3
Default statement
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goto statement

• C Provides the goto statement to transfer control
  unconditionally from one place to another place
  in the program.
• A goto statement can cause program control almost
  anywhere in the program unconditionally.
• The goto statement requires a label to identify
  the place to move the execution.A label is a
  valid variable name and must be ended with
  colon().
• Syntax
• goto label label
• .
• .
• label goto label

25

• Example
• includeltstdio.hgt
• void main()
• int a,b
• printf(\n Enter the number)
• scanf(d d,a,b)
• if(ab)
• goto equal
• else
• printf(\n A and b are not equal)
• exit(0)
• equal
• printf(A and B are equal)

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switch statement

• The switch statement is used to pickup or execute
  a particular group of statements from several
  available group of statements.
• It is multiway decision statement it test the
  value of given variable or expression a list of
  case values when a match is found, a block of
  statements associated with case is executed.
• Syntax
• switch(expression)
• case label1
• statements
• break
• case label2
• statements
• break
• default
• statements
• break

27
switch
case 1 statements
case 2 statements
case 3 statements
28

• Rules for writing switch() statement
• 1.The expression in switch statement must be an
  integer value or a character constant.
• 2.No real numbers are used in an expression.
• 3.Each case block and default blocks must be
  terminated with break statements.
• 4.The default is optional and can be placed
  anywhere, but usually placed at end.
• 5.The case keyword must terminate with colon().
• 6.No two case constants are identical.
• 7.The case labels must be constants.
• 8.The value of switch expression is compared with
  the case constant expression in the order
  specified.
• 9.In the absence of break statement, all
  statement that are followed by matched by matched
  cases are executed.

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• Example
• includeltstdio.hgt
• void main()
• int a1
• switch(a)
• case 1
• printf(I am in case 1 \n)
• break
• case 2
• printf(I am in case 2 \n)
• break
• case 3
• printf(I am in case 3 \n)
• break

30

• Comparison of switch() case and Nested if

Switch() Case nested if
The switch() can test only constant values. The if can evaluate relational or logical expression
No two case statement have identical constants in the same switch. Same conditions may be repeated for number of times
Character constants are automatically converted to integers. Character constants are automatically converted to integers.
In switch() case statement nested if can be used. In nested if statements, switch case can be used.
31

• Branching and Looping
• Repeat a set of instructions in specified number
  of times or until a particular condition is
  statified.This reparation is known as Looping.
• The loop in a program consists of 2 parts
• 1.body of the loop
• 2.Control statement
• The control statement is used to test a condition
  and the body of the loop executed repeatedly.
• In C there are 3 looping constructs

1.for loop 2.while loop 3.dowhile loop
32

• while loop
• In while, used to execute the statements within
  the body until the condition becomes false.
• The while loop statement, the condition is
  evaluated first if it is true, the body of the
  loop evaluated. The process is repeated until the
  test condition false, then the control is
  transferred out of the loop.

T
Condition
True statement
F
33

• Syntax
• while(text expression)
• sequence of statements
• Example / Addition of numbers upto 10 using
  while loop
• includeltstdio.hgt
• void main()
• int i1,sum0
• while(ilt10)
• sumsumi
• i
• printf(The sum of numbers upto 10
  is d,sum)

34

• dowhile loop
• do-while is an exit control loop statement
  i.e., condition is tested only after executing a
  loop. In some situations it may be necessary to
  execute the body of the loop before the test
  condition is performed, in such a situation
  dowhile loop is useful.
• Syntax
• do
• body of the loop
• while (condition)

Body of the loop
T
Condition
F
35

• /Addition of numbers using dowhile loop /
• includeltstdio.hgt
• void main()
• int i1,sum0
• do
• sumsumi
• i
• while(ilt10)
• printf((The sum of numbers upto 10 is
  d,sum)

36

• / Program to print n numbers using dowhile loop
  /
• includeltstdio.hgt
• includeltconio.hgt
• void main()
• int i,n
• printf(Enter the number)
• scanf(d,n)
• i0
• do
• printf(the number are d \n,i)
• ii1
• while(iltn)

37

• Comparison between while and do while statements.

while dowhile
This is the top tested loop This is the bottom tested loop
The condition is first tested, if the condition is true then the block is executed until the condition becomes false. It executes the body once, after it checks the condition, if it is true the body is executed until the condition
Loop will not be executed if the condition is false. Loop will be executed atleast once even though the condition is false.
38

• for loop
• The for loop is another repetitive control
  structure. and is used to execute set of
  instructions repeatedly until the condition
  becomes false.
• The assignment,incrementation or decrementation
  and condition checking is done in for statement
  only, where other control structures are
• Syntax
• for(initialization text-expression
  updation)
• statements

39

• 1.Initialization statement is executed.
• 2.Test-expression is evaluated.
• 3.If the test-expression evaluates to true, the
  statements in the body of the loop would get
  executed.
• 4.Control goes to the updation statement, the
  updation statement is executed, which changes the
  value of the loop variable.
• 5.Test-expression is again evaluated.
• 6.If it evaluates to true, again the statements
  in the body of the loop would get executed.
• 7.Conrol once again goes back to the updation
  statement, which updates the looping variable.
• The sequence is repeated as long as the
  test-expression to true. Once the test-expression
  evaluates to false, the loop is exited and the
  control is transferred to the first statement
  following the looping construct.

40
Initialization
Test-expression
Next Statement
T
Statements
41

• / To find sum of N natural numbers using
  for-loop /
• includeltstdio.hgt
• void main()
• int n,i,sum
• printf(Enter a number \n)
• scanf(d,n)
• sum0
• for(i1iltni)
• sumi
• printf(Sumd \n,sum)

42

• / To Print numbers from 1 to 10 and their
  squares /
• includeltstdio.hgt
• void main()
• int i
• printf(Number \t Squares \n)
• for(i1ilt10i)
• printf(d \t\t d \n,ii)
• printf(\n Press any key to continue)

43

• Nested Loops
• Any loop can be placed within another loop.
  Such loops are called nested loops.
• Rules for implementing the nested for loop
• 1.Each loop should have a unique index variable.
• 2.The loops should not overlap each other.
• 3.The loops should be completely embedded within
  each other.
• 4.The loop can have any number of exit points
  inside the range, but should not permit entry to
  it.
• Syntax
• for(initialization text-expression
  updation)
• for(initializationtext-expressionupdatio
  n)
• statements
• statements

44

• / Program for Pascaline triangle /
• includeltstdio.hgt
• void main()
• int i,j
• for(i1ilt5i)
• for(j1jltij)
• printf("d\t",i)
• printf("\n\n")

45

• Comma Operator
• The (,).
• comma operator is used primarily in association
  with the for statement. This operator permits
  two different expressions to appear .
• Two or more variables van be initialized and used
  in the for statement using a comma operator.
• Syntax 1
• for(expression1a,expression1bexpression2exp
  ression3)
• statements
• where expression1a and expression1b are two
  expressions separated by the comma operator.
  These two expressions initialize two separate
  indices that would be simultaneously used within
  the for loop.

46

• / Program prints the numbers from 1 to 10 and 10
  to 1 /
• void main()
• int a,b
• for(11,b10alt10a,b--)
• printf(ad,bd,a,b)
• Syntax 1
• for(expression1expression2expression3a,expr
  ession3b)
• statements
• where expression 3a and expression 3b
  separated by the comma operator.

47

• / Program for print numbers from 1 to 10 /
• includeltstdio.hgt
• void main()
• int a,b
• for(a0,b10a!ba,b--)
• printf(ad,bd,a,b)

48

• break statement
• The break statement is used to terminate loops or
  exit from a switch.
• It can be used within a do-while,for and switch
  statement.
• When used within a switch-case statement, control
  is transferred to the end of the construct.
• Example
• includeltstdio.hgt
• void main()
• int x1
• while(xlt10)
• printf(xd \n,x)
• if(x5)
• break
• x

49

• Continue Statement
• The continue statement can be used to skip the
  rest of the body of an iterative loop.
• Syntax
• continue
• The continue statement can be included only in
  a while,do-while or for statement. It is simply
  written as continue.

50

• / To print odd numbers using coninue statement
  /
• includeltconio.hgt
• void main()
• unsigned x
• x0
• clrscr()
• while(xlt10)
• x
• if(x20)
• continue
• printf("i is an odd number. \n",x)

51

• Difference between While-loop Do-while-loop

While-Loop Do-While Loop
Entry-Controlled Loop Exit-Controlled Loop
Loop Condition has to be initiallyTRUE for body to be executed. Loop body will be executed at-least once
If the condition is false then the statement block will not be executed even once. In the test condition is false then the statement block will be executed at least once.
Syntax           exp1          while(exp2)                     statement...           statement...           exp3          Syntax           do                      statement...           statement...          while(condition)
The semicolon is not necessary after the test condition. The semicolon is must after the test condition.
52

• Library Functions
• Library functions are also known as pre-defined
  functions (or) build-in functions.Pre-defined
  functions are functions not to be written by the
  programmer.
• A library function is accessed simply by writing
  the function name, followed by a list of
  arguments. The arguments must be enclosed in
  parentheses.
• A library function can be categorized with 4
  types
• 1.Mathematical functions
• 2.Character functions
• 3.Input and Output functions
• 4.String functions

53

• Mathematical functions
• In C Programming mathematical functions reside in
  math.h header files.

Function Description Example
pow() This function is used to compute the x raised to y. Syntax pow(x,y) pow(3,4)64
sin() It is used to find the sine of angle in radians. Syntax sin() sin(30)0.5
cos() It is used to find the cosine value of angle in radians. Syntax cos() cos(30)0.866
tan() It is used to compute the tangent value of angle in radians. Syntax tan() tan(30)0.577
exp() This function computes the exponent value of x. Syntax exp() exp(30)1.6876
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Function Description Example
sqrt() It is used to compute the square root value of x. sqrt(25)5
abs() It is used to find the absolute value of a number as an integer. abs(-15)15 abs(15)15
ceil() This function is used to return the smallest integer valued greater than or equal to x. ceil(15.99)16 ceil(15.01)16
floor() This function is used to returns the greatest integer value lesser than or equal to x. floor(15.99)15 floor(15.01)15
log10() This function return the logarithms to the base 10 of x. log10(10)1
55

• Example
• includeltstdio.hgt
• includeltmath.hgt
• void main()
• printf(pow(4,3)f,pow(4,3))
• printf(sin(30)f,sin(303.14/180.0))
• printf(sqrt(25)f,sqrt(25))
• printf(abs(-15)d,abs(-15))
• printf(ceil(15.99)f,ceil(15.99))
• printf(floor(15.99)f,floor(15.99))
• printf(log10(10)f,log10(10))

56

• Character functions
• In C Programming character functions reside in
  ctype.h header files.

Function Description Example
isalnum() This function is used to check whether a character is an alphanumeric(i.e A to Z or a to z) or (0 to 9). isalnum(a)True(True means non zero value). isalnum()False
isalpha() This function is used to test whether the given character is alphabetic character or not. isalpha(a)True(1) isalpha(5)False(0)
isdigit() This function is used to check whether or not it is a digit(0 to 9). isdigit(9)True isdigit(a)False
islower() This function is used to check whether the given character is lower case or not(a to z). islower(a)True islower(A)False
isupper() This function is used to check whether the given character is uppercase letter or not(A to Z). isupper(a)False Isupper(A)True
57
Function Description Example
isspace() This function is used to check whether a given character is white space or not. isspace( )True Isspace(a)False
isascii() This function is used to test if the parameter is between 0 to 127. isascii(97)True Isascii(200)False
tolower() If the character is an uppercase character(A to Z),then it is converted to lower case. Tolower(a)A
toupper() If the character is an lower case character(a to z),then it is converted to upper case(A to Z). toupper(a)A
toascii() This function is used to convert the character to its equivalent ascii value. toascii(A)65 toascii(a)97
58

• Example
• includeltstdio.hgt
• includeltctype.hgt
• void main()
• printf(isalnum(a)d,isalnum(a)
• printf(isalpha(a)d,isalpha(a))
• printf(isdigit(9)d,isdigit(9))
• printf(isupper(a)d,isupper(a))
• printf(isspace()d,isspace())
• printf(isascii(97)d,isascii(97))
• printf(tolower(A)c,tolower(A))
• printf(toupper(a)c,toupper(a))
• printf(toascii(A)d,toascii(A))

59

• Input/Output functions
• In C Programming character functions reside in
  stdio.h header files.
• The functions are scanf,printf,putc,getc.
• String functions
• In C Programming string functions reside in
  string.h header files.
• The following string manipulations are,
• 1.String Copy(strcpy) function
• 2.String Lengrh(strlen) function
• 3.String Concatenation(strcat) function
• 4.String Compare(strcmp) function
• 5.String Reverse(strrev) function
• 6.String Upper(strupr) function

60

• 1.String Copy(strcpy) function
• This function is used to copy the content of one
  string into another string.
• Syntax
• strcpy(string1,string2)
• Where,
• Here,the contents of the string str2 is
  copied into the string str1
• The str2 remains unchanged.
• Example
• includeltstdio.hgt
• includeltstring.hgt
• void main()
• char name20
• strcpy(name,"Vels University")
• puts(name)

61

• 2.String Lenth(strlen) function
• This function is used to find out the number of
  characters in the given string.
• Syntax
• nstrlen(str)
• where, n-is an integer variable which receives
  the length of string
• str-valid string variable or constant.
• Example
• includeltstdio.hgt
• includeltstring.hgt
• void main()
• char a100
• int length
• printf(Enter a string to calculate its
  length)
• gets(a)
• lengthstrlen(a)
• printf(Length of entered string isd
  \n,length)

62

• 3.String Concatenation(strcat) function
• This function is used to join two strings.
• Syntax strcat(str1,str2)
• This function is executed, the contents of str2
  are joined with str1 and the character \0 is
  placed at the end of the new string str1.The
  string str2 remains unchanged.
• Example
• includeltstdio.hgt
• includeltconio.hgt
• void main()
• char str130,str210
• printf(Enter string1 \n)
• gets(str1)
• printf(Enter string2 \n)
• gets(str2)
• strcat(str1,str2)
• printf(Sting1\n)
• puts(str1)

63

• 4.String Compare(strcmp) function
• This function strcmp() is used to compare two
  strings.
• Syntax
• strcmp(str1,str2)
• IF the two strings str1 and str2 are equal
  then the value of the function returns the value
  zero. If str1 is greater than str2 the function
  returns positive integer else it returns negative
  integer.
• Example
• includeltstdio.hgt
• includeltstring.hgt
• void main()
• char word120,word220
• int i
• printf(Enter the first string \n)
• scanf(s,word1)
• printf(Enter the second string \n)
• scanf(s,word2)

64

• if(i0)
• printf(The words are identical \n)
• else
• printf(Words are not identical \n)
• 5.String Reverse(strrev) function
• This function is used to reverse a string.
• Syntax
• strrev(str)

65

• includeltstdio.hgt
• void main()
• char s1
• printf(Enter the string)
• gets(s1)
• strrev(s1)
• printf(\n The reversed string is..s,s1)

66

• 6.String Upper(strupr) function
• This function is used converts S to all uppercase
  characters.
• Syntax
• strupr(str)
• Example
• includeltstdio.hgt
• void main()
• char s1
• printf(\n Enter the string1 in lower case
  or in combination of upper
• lower case\n)
• gets(s1)
• strupr(s1)
• printf(\n The entered string is..s,s1)

67

• Tokens
• A token is an entity in a program. Whenever the
  program is submitted for compilation,te compiler
  identifies and splits the program into a sequence
  of tokens.
• A token may be a single character and a set of
  characters with a specific meaning.
• The following are tokens available in C.
• 1.Keyword
• 2.Constants
• 3.Identifiers
• 4.Punctuation symbols(separators)
• 5.Operators