Unit – IV introduction to c overview of c

• 
  C is portable, structured programming language.
  
• 
  It is robust, fast and extensible.
  
• 
  It is used for complex programs.
  
• 
  The root of all modern language is ALGOL (1960).
  
• 
  BCPL (Basic Combined Programming Language)-1967. -- a user friendly OS providing powerful development tools developed from BCPL. Assembler tedious long and error prone.
  
• 
  A new language ``B'' a second attempt. c. 1970.
  
• 
  A totally new language ``C'' a successor to ``B''. c. 1971
  
• 
  By 1973 UNIX OS almost totally written in ``C''.
  

Some of C's characteristics that define the language and also have lead to its popularity as a programming language.

• 
  Small size
  
• 
  Supports variety of data types and a set of operators.
  
• 
  Extensive use of function calls
  
• 
  Enables the implementation of hierarchical and modular programming with the help of functions.
  
• 
  C can extend itself by addition of functions to its library continuously.
  
• 
  Structured language
  
• 
  Low level (BitWise) programming readily available
  
• 
  Pointer implementation - extensive use of pointers for memory, array, structures and functions.
  
• 
  C has now become a widely used professional language for various reasons.
  

• 
  It has high-level constructs.
  
• 
  It can handle low-level activities.
  
• 
  It produces efficient programs.
  
• 
  It can be compiled on a variety of computers.
  

• 
  Constants in C are applicable to values, which do not change during the execution of a program.
  
• 
  C constants are classified as
  

• 
  Numeric constants
  
  • 
    Integer constants
    
  • 
    Real constants
    
• 
  Character constants
  
  • 
    Single character constants
    
  • 
    String constants
    

1. 
   Numeric constants
   

• 
  Sequence of numbers from 0 to 9 without decimal point or fractional part or any other symbols.
  
• 
  Minimum 2 bytes, maximum 4 bytes.
  
• 
  It may be positive or negative or zero
  
• 
  Eg:10,+30,-15
  

• 
  floating point constants
  
• 
  many parameters are defined in real constants like height,length,distance.
  
• 
  Eg:2.5,3.14
  
• 
  It can be written in exponential notation.
  

2. 
   Character constants
   

1. 
   Single character constant
   

• 
  Single character
  
• 
  Single digit or single special symbol or white space enclosed within a pair of single quote marks.
  
• 
  Characters constants have integer values known as ASCII values.
  
• 
  Eg:’a’,’8’,’u’
  

2. 
   String constants
   

• 
  Sequence of characters enclosed within double quote marks.
  
• 
  String may be a combination of all kinds of symbols.
  
• 
  Eg:”hello”,”India”,”444”,”a”
  

• 
  During program execution, value of variables can be changed.
  
• 
  Variable can be of different data types.
  
• 
  Variable is a data name used for storing a data value.
  
• 
  Value may be changed during program execution
  
• 
  Variable name may be declared based on the meaning of the operation.
  
• 
  Eg: height, average, sun.
  

• 
  Must begin with a character without spaces but underscore is permitted.
  
• 
  Length of the variable varies from a computer to another.
  
• 
  Variable should not be a C keyword.
  
• 
  May be a combination of lower and upper characters.
  
• 
  Variable should not start with digit.
  

• 
  C support variety of data types.
  
• 
  Data is represented using numbers or characters.
  
• 
  C is a so called type safe programming language, that is, any variable needs to be assigned a supported data type. C supports the following data types:
  

• bool

• short

• double

• long

• unsigned char, int, short,

/* customized or non-elementary data types */

• struct

Char 1 %c

Unsigned char 1 %c

Short or int 2 %i or %d

Unsigned int 2 %u

Long 4 %ld

Unsigned long 4 %lu

Float 4 %f or %g

Double 8 %lf

Long double 10 %lf

• 
  Should be done in declaration part of the program.
  
• 
  Compiler obtains the variable name.
  
• 
  It tells the compiler the data type of the variable being declared and helps in allocating the memory.
  

int age;

• 
  Variables declared can be assigned or initialized using an assignment operator “=”.
  

Variable-name = constant

Or

Data-type variable –name = constant

int x, y,z;

3. 
   OPERATORS & EXPRESSIONS
   

1. Arithmetic operators +,-,*,/ and %

2. Relational Operators >,<,==,>=,<=,!=

3. Logical Operators &&,||,!

4. Increments and Decrement Operators ++,--

5. Assignment Operators =

6. Bitwise Operators &,/,>>,<<,~

7. Comma operator ,

8. Conditional Operators ?:

1. 
   Arithmetic Operators
   

+ Addition or Unary Plus

– Subtraction or Unary Minus

• 
  Multiplication
  

% Modulus Operator

Examples of arithmetic operators are

x + y

-x + y

-a * b

2. 
   Relational Operators
   

> is greater than

>= is greater than or equal to

== is equal to

!= is not equal to

A simple relational expression contains only one relational operator and takes the following form.

Where exp1 and exp2 are expressions, which may be simple constants, variables or combination of them. Given below is a list of examples of relational expressions and evaluated values.

3. Logical Operators

C has the following logical operators, they compare or evaluate logical and relational expressions.

Operator Meaning

&& Logical AND

|| Logical OR

! Logical NOT

(&&) Logical AND

This operator is used to evaluate 2 conditions or expressions with relational operators simultaneously. If both the expressions to the left and to the right of the logical operator is true then the whole compound expression is true.

Example

a > b && x = = 10

The expression to the left is a > b and that on the right is x == 10 the whole expression is true only if both expressions are true i.e., if a is greater than b and x is equal to 10.

4. 
   Increment and decrement operator:
   

Eg:i++;

5. 
   Assignment Operators
   

The Assignment Operator evaluates an expression on the right of the expression and substitutes it to the value or variable on the left of the expression

.

Example

Here the value of a + b is evaluated and substituted to the variable x.

In addition, C has a set of shorthand assignment operators of the form.

var oper = exp;

Here var is a variable, exp is an expression and oper is a C binary arithmetic operator. The operator oper = is known as shorthand assignment operator

6. 
   Bitwise operator
   

>> right shift

^ bitwise XOR

~ one’s complement

& bitwise AND

| bitwise OR

7. Comma operator

It is used to separate two or more expressions.

Eg:a=2,b=4,c=a+b;

8. 
   Conditional operator
   

If the condition true,the expression 1 is evaluated.

If the condition is false,the expression2 is evaluated.

Expressions

Arithmetic Expressions

An expression is a combination of variables constants and operators written according to the syntax of C language. In C every expression evaluates to a value i.e., every expression results in some value of a certain type that can be assigned to a variable. Some examples of C expressions are shown in the table given below.

Algebraic Expression C Expression

a x b – c a * b – c

(m + n) (x + y) (m + n) * (x + y)

(ab / c) a * b / c

3x2 +2x + 1 3*x*x+2*x+1

(x / y) + c x / y + c

Expressions are evaluated using an assignment statement of the form

Variable is any valid C variable name. When the statement is encountered, the expression is evaluated first and then replaces the previous value of the variable on the left hand side. All variables used in the expression must be assigned values before evaluation is attempted.

Example of evaluation statements are

x = a * b – c

y = b / c * a

z = a – b / c + d;

The following program illustrates the effect of presence of parenthesis in expressions.

An arithmetic expression without parenthesis will be evaluated from left to right using the rules of precedence of operators. There are two distinct priority levels of arithmetic operators in C.

High priority * / %

Low priority + -

• First parenthesized sub expression left to right are evaluated.

• If parenthesis are nested, the evaluation begins with the innermost sub

expression.

• The precedence rule is applied in determining the order of application of

operators in evaluating sub expressions.

• The associability rule is applied when two or more operators of the same

precedence level appear in the sub expression.

• Arithmetic expressions are evaluated from left to right using the rules of

precedence.

• When Parenthesis are used, the expressions within parenthesis assume highest

priority.

Each operator in C has a precedence associated with it. The precedence is used to determine how an expression involving more than one operator is evaluated. There are distinct levels of precedence and an operator may belong to one of these levels. The operators of higher precedence are evaluated first. The operators of same precedence are evaluated from right to left or from left to right depending on the level. This is known as associativity property of an operator.

Input/Output functions are classified into two types. They are,

• 
  Formatted functions
  
• 
  Unformatted function
  

• 
  Read and write all types of data values.
  
• 
  Require conversion symbol to identify the data type.
  
• 
  Return the values after execution.
  

• 
  Only work with character data type.
  
• 
  Do not require conversion symbol for identification of data type.
  
• 
  Return values are always same.
  

Formatted Functions:

• 
  Prints all types of data values to the console.
  
• 
  Requires conversion symbol and variable names to print the data.
  

main ()

int x=2;

char z=’c’;

printf(“%d %f %c”,x,y,z);

}

Output

• 
  Reads all type of data values
  
• 
  It is used for run time assignment of variables.
  
• 
  Requires conversion symbol to identify the data to be read
  

scanf(“%d %f%c”,&a,&b,&c);

&-address operator-:

• 
  prints the memory location of the variable.
  
• 
  It indicates memory location,so that the value read would be placed at that location.
  
• 
  It also returns values.
  
• 
  Return value is exactly equal to the number of values correctly read.
  
• 
  If any mismatch error will shown.
  

#include

#include

main()

int a;

printf(“Enter the value of A”);

scanf(“%c”,&a);

printf(“A=%c”,a);

}

Output:

A=8

printf(),scanf() statements follow a combination of characters called as escape sequences.It starts with ‘\’

\ n newline

\ b backspace

\ f formfeed

\ ‘ singlequote

\\ backslash

\0 NULL

\ r carriage return

\ a alert(bell)

\’’ double quotes

\ v vertical tab

\ ? question mark

Eg:Average of three real numbers.

#include

#include

main()

float a,b,c,d;

clrscr();

printf(“Enter three float numbers:\n”);

scanf(“\n %f %f %f”,&a,&b,&c);

d=a+b+c;

}

Output:

Average of given numbers: 3.5

There are three types of I/O functions.

1. 
   Character I/O
   
2. 
   String I/O
   
3. 
   File I/O
   

1. 
   getchar()
   

• 
  It reads character type data from the standard input.
  
• 
  It reads one character at a time till the user presses the enter key.
  

2. 
   putchar()
   

• 
  It prints one character on the screen at a time , which is read by the standard input.
  

3. 
   getch() and getche()
   

• 
  These functions read any alphanumeric characters from the standard input device.
  
• 
  Character entered is not displayed by getch() function
  

4. 
   putch()
   

• 
  It prints any alphanumericcharacter taken by the standard input device.
  

a) gets()

• 
  It is used for accepting any string through stdin keyboard until enter key is pressed.
  
• 
  stdio.h is needed for implementing the above function.
  

• 
  It prints the string or character array.
  

• 
  It reads strings from the console.
  
• 
  Syntax: cgets(char *st);
  

• 
  It displays string on the console.
  
• 
  Syntax : cputs(char *st);
  

fprintf() - write values to files.

fscanf() - read values from files.

getc() - reads a single character from operand file and moves the file pointer.

putc()- write a single character into a file.

fgetc() - reads a character and increase the file pointer position.

fputc() - writes character to file shown by the file pointer.

fgets() - reads the string.

fputs() - write the string to operand file.

putw() - write an integer value to file.

getw() - returns the integer value and increase the pointer.

Commonly used library functions:

1. 
   clrscr() - clear the screen -> conio.h
   
2. 
   exit () - terminates the program->process.h
   
3. 
   sleep() -pause the execution of program for a given number of seconds-dos.h
   
4. 
   system () - helpful in executing different dos.
   

• 
  Program is the execution of one or more instructions.
  
• 
  Based on the condition, the order of execution may change.
  
• 
  On the basis of applications it is essential to
  

• 
  Alter the flow of a program.
  
• 
  Test the logical conditions.
  
• 
  Control the flow of execution as per the selection.
  

• 
  C language supports the control statements as listed below.
  

• 
  if statement
  
• 
  if-else
  
• 
  if-else….if
  
• 
  switch() case
  

1. 
   if statement:
   

eg:

printf(“a is greater”);

2. 
   if-else:
   

Eg:

printf(“a is greater”);

else

printf(“b is greater”);

3. 
   Nested if-else:
   

• 
  Nested if else can be chained with one another.
  
• 
  If condition is false, control passes to else block.
  
• 
  If one of the ‘if’ statement satisfies the condition, other nested else if will not be executed.
  

#include

#include

main()

int a,b,c,big;

clrscr();

printf(“Enter three numbers”);

scanf(“%d %d %d”,&a,&b,&c);

if(a>b)

big=a;

big=c;

if(b>c)

else

printf(“\n Biggest number is %d “,big);

getch();

}

Output:

Biggest number is 18

4. 
   switch()
   

• 
  It is multiway branch statement.
  
• 
  It requires only one argument of any data type, which is checked with number of case options.
  
• 
  If value matches with case constant, particular case statement is executed.
  
• 
  If not matched, default is executed.
  
• 
  Every case terminates with ‘:’ symbol.
  
• 
  break is used to exit from current case.
  

switch (variable or expression)

{

case constant A:

break;

Statement;

break;

default:

}

Eg: Program to find value of y

#include

#include

main()

{

int n;

float x,y;

clrscr();

printf(“\n Enter values to x and n:”);

scanf(“%f %d”,&x,&n);

switch(n)

{

case 1: y=1+x;

break;

case 2: y=1-x;

break;

case 3: y=1+pow(x,n)

break;

default: y=1+n*x;

break;

}

printf(“\n value of y(x,n)=%f),y);

getch();

}

Output:

Enter value to x and n: 0.42 5

Value of y(x,n)=3.10

break statement:

• 
  It allows programmers to terminate the loop.
  
• 
  It skips from loop or block in which it is defined.
  

continue statement:

• 
  It is opposite to break.
  
• 
  Continuing next iteration of loop statements.
  
• 
  It does not terminate, bit it skips the statements.
  

goto statement:

• 
  It does not require any condition.
  
• 
  It passes control anywhere in the program
  
• 
  Syntax: goto label;
  

Eg: even or odd using goto.

#include

#include

#include

main()

{

int x;

clrscr();

printf(“\n Enter a number:”);

scanf(“ %d”,&x);

if( x%2==0)

goto even;

else

goto odd;

even:

printf(“\n %d is even number”);

return;

odd:

printf(“\n %d is odd number”);

}

Output:

Enter a number: 5

5 is odd number.

Difference between break and continue

break	continue
Exits from current block or loop	Loop takes next iteration
Control passes to nest statement	Control passes to the beginning of loop
Terminates the program	Never terminates the program

5. 
   BRANCHING AND LOOPING:
   

• 
  Branching and looping are used for repetitive tasks.
  
• 
  Loop:
  

A loop is defined as a block of statements which are repeatedly executed for certain number of times.

• 
  Terms in loop are
  

• 
  Loop variable
  
• 
  Initialization
  
• 
  Incrimination or decrimination
  

• 
  Loops in C language are
  

• 
  for()
  
• 
  while()
  
• 
  do while()
  

1. 
   for loop
   

• 
  It allows for executing a set of instructions until a certain condition is satisfied.
  

Syntax:

for (initialize;test condition;re-evaluation parameter)

{

Statement;

Statement;

}

Formats:

for (;;)	infinite loop	no arguments
for (a=0;a<=20;)	infinite loop	a is neither increased nor decreased
for( a=0;a<=10;a++) printf(“%d”,a);	displays value from 0 to 10	value of a is displayed from o to 10
for(a=10;a>=0;a--) printf(“%d”,a)	displays value from 10 to 0	a is decreased from 10 to 0

Eg: display numbers from 1 to 15 using for loop

#include

#include

main()

{

int i;

clrscr();

for( i=1;i<=15;i++)

printf(“%d”,i);

}

Output:

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Nested for loops:

Using loop within loop

Eg: finding perfect cubesof1,2,3,4

#include

main()

{

int i,j,k;

clrscr();

printf(“Enter a number”);

scanf(“%d”,&k);

for(i=1;i

{

for(j=1;j<=I;j++)

{

if(i==pow(j,3))

printf(“\n Number: %d & its cube :%d”j,i);

}

}

}

Output:

Enter a number: 1000

Number:1 & its cube :1

Number:2 & its cube :8

Number:3 & its cube :27

Number:4 & its cube :64

2. 
   While loop:
   

syntax:

while (test condition)

{

Body of the loop;

}

• 
  Loop statements will be executed till the condition is true.
  
• 
  Test condition is evaluated and if the condition is true, body of the loop is executed.
  
• 
  When condition becomes false the execution will be out of the loop.
  

Eg: add 10 consecutive numbers starting from 1

main()

{

int a=1;sum=0;

clrscr();

while(a<=10)

{

printf(“%d”,a);

sum=sum+a;

a++;

}

printf(“\n Sum of 10 numbers:%d”,sum);

}

Output:

1 2 3 4 5 6 7 8 9 10

Sum of 10 numbers: 55

3. 
   do-while loop:
   

syntax:

do

{

Statement;

}

while (condition);

• 
  condition is checked at the end of the loop.
  
• 
  do-while loop will execute atleast one time even if the condition is false initially.
  
• 
  do-while loop executes until the condition becomes false.
  

Eg:

main()

int i=1;

clrscr();

do

{

printf(“\n This is a program of do while loop”);

i++;

}

while(i<=5);

}

Output:

This is a program of do while loop

This is a program of do while loop

This is a program of do while loop

This is a program of do while loop

This is a program of do while loop

4. 
   do while statement with while loop
   

syntax:

do while(condition)

{

Statements;

}

while(condition);

Eg: Print values from 1 to 5 using while statement in do while loop

main ()

{

int x=0;

clrscr();

do while(x<5)

{

x++;

printf(“\t %d”,x);

}

while(x<1);

}

Output

1 2 3 4 5

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storage -> What do you love?
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storage -> Central allandale By Jackie Potts
storage -> Working Paper By
storage -> Td toronto jazz festival
storage -> Curriculum Vitae May 15, 2014 Bruno Golosio

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