unit 1for civil

8/3/2019 UNIT 1for Civil

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C FUNDAMENTALSPrepared by

S.Gunasekaran B.E,7/1/2011

This unit is explained about the fundamentals of C language such as C character set-Identifiers and

keywords-Data types-Constants-Variables-Declaration-Expressions-Statements-Symbolic constants-

Operators-Data input and output-control statements-Unconditional statements, nested loop.


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HISTORY OF C LANGUAGE

C is one of the most popular programming languages. It was developed by Dennis

Ritchie at AT & Ts Bell Laboratories at USA in the early 1970s. It is an upgraded version of

two earlier languages, called Basic Combined Programming Language (BCPL) and B, which

were also developed at Bell laboratories. The following table illustrates the history of C

language.

Language Year Founder

ALGOL 1960 International group

BCPL 1967 Martin Richards

B 1970 Ken Thompson

C 1972 Dennis Ritche

K&RC 1978 Kernighan and Ritche

ANSI C 1989 ANSI Committee

ANSI/ISO C 1990 ISO Committee

C IS A MIDDLE LEVEL LANGUAGE

a)

Low level language: Low level language is in terms of 0s and 1s (bits). Clanguage has the certain features of Low-level Language, that allow the

programmer to carry out operations on bits that are normally available in Assembly

language or Machine language.

b) High level language: High level language looks like normal English, whoseinstruction set is more compatible with human languages. These languages are easily

understandable and designed to provide a better program efficiency. These are

machine independent. Examples are FORTAN, PASCAL, COBOL, BASIC, C++

etc.

c) Middle level language: C lies in between these two categories it is neither a lowlevel language nor a high level language, it is a middle level language. i.e., performs

the task of Low level language as well as high level language. We can write the code

for Operating System, Application Programs, and Assembly language programs in

C language. Unix Operating System is written in C language.


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STRUCTURE OF A C PROGRAM

There are some sections in C program given below:

i) Documentation SectionIt consists of set of comment lines used to specify the name of program,

author and other details etc.,

Comments: It is helpful in identifying the program features and

underlying logic of the program. The line begins with /* and ending with */.

These are not executable, the compiler is ignored anything between /* and */.The

new style is //

ii) Preprocessor Section

Definition sectionIt is used to link system library files, for defining the macros and

for defining the conditional inclusion.

Eg: #include, #define A 10, #if def, #endif etc.

iii) Global Declaration SectionThe variables that are used in more than one function throughout the

program are called global variables and declared outside of all the function i.e.,

before main(). It has two parts:

Declaration part to declare all the variables used in the program

Execution part Contains at least one valid C statement. It begins with

opening braces {and ends with closing braces }. The

closing brace of main function is the logical end of theprogram.

iv) Sub Program Section It contains the function definitions included.

The following tables are explained the programming structure.


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STRUCTURE SAMPLE

documentation section

preprocessor section

definition section

global declaration section

main()

{

declaration part;

execution part;

}

sub program section

{

Body of the subprogram;

}

/* finding area of circle */

#include

#define PI 3.14

main()

{

int r=5;

float area;

area = PI * r * r;

printf(Area of circle: %f, area);

}

OUTPUT:

Area of circle: 78.5

CHARACTER SET

Character set is the fundamental raw material of any language and they are used to

represent information. C language consists of two character set namely,

a) Source character setb) Execution character set

Source Character Set

These are useful to construct the statements in the source program Alphabets Upper

case AZ,Lower case az ,Digits 0,19 ,Special character , + - * / $ _ { [ ] < > \ |

~ @ # % ^ & : ; ?

Execution Character Set

These are employed at the time of execution. This set of characters are also called as non

graphic characters because, these characters are invisible and cannot be printed or displayed

directly. This will be effect when program is being executed. Execution characters set are always

represented by a backslash (\) followed by a character. We simply call it as escape sequences.


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CHARACTER ESCAPE SEQUENCE

Bell (alert) \a

Backspace \b

Horizontal tab \t

Vertical tab \v

Newline (Line feed) \n

Form feed \f

Carriage return \r

Quotation Mark \

Apostrophe \

Question Mark \?

Back Slash \\

Null \0 (indicate end of string)

C TOKENS

The individual units of C programming language are called C tokens. It is usually

referred as individual text and punctuation in a passage of text and has the following types

C Tokens

Identifiers Keywords Constants Strings OperatorsSpecial

Symbols

Total,

Age

int,

double,

39,

39.77

Guna

Vikram

+, -, *, / #, $, %


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IDENTIFIERS

Identifiers are referring to the names of variable, functions and arrays.

RULE FOR NAMING AN IDENTIFIERS

First character must be an alphabet Must consist of only letters, digits or underscore Only first 31 characters are significant Must not contain white space

The following are valid

Salary, aug99_sales, I, index

The following are not valid

2001_sales, aug99+sales, my age, printf

KEYWORDS

There are certain reserved words called keywords that have standard and predefinedmeaning in C language, which cant be changed.

All keywords are fixed meanings and these meanings are cant be changed Keywords serve as basic building blocks for program statementsExample:

Auto, double, int, struct, break, else, case, char, float, for

DATA TYPES

Data type is the type of the data, which are going to access within the program. C

supports different data types. Each data type may have predefined memory requirement and

storage representations in program.


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6 # 55They are four data types:

Primary C

Data TypeUser defined Derived Empty

Charint

float

double

typedefenum

arrayspointers

structures

union

void

Basic data types:

Type Keyword

Character char

Integer int

Floating point float

Doublefloating point

double

Valueless void

Several of the basic types can be modified using one or more of these type modifiers:

signed

unsigned

short

long

The type modifiers precede the type name that they modify. The basic arithmetic types,

including modifiers, allowed by C are shown in the following table along with their guaranteed

minimum ranges. Most compilers will exceed the minimums for one or more types. Also, if your

computer uses twos complement arithmetic (as most do), then the smallest negative value that

can be stored by a signed integer will be one more than the minimums shown. For example, the

range of an int for most computers is 32,768 to 32,767. Whether type char is signed or

unsigned is implementation dependent.


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Type Byte Minimum Range

CHARACTER TYPE

char 127 to 127 or 0 to 255

unsigned char 1 bytes 0 to 255

signed char 127 to 127

INTEGER TYPE

Int 2 bytes 32,767 to 32,767

unsigned int 2 bytes 0 to 65,535

signed int 2 bytes same as int

short int 1 bytes same as int

unsigned short

int

1 bytes 0 to 65,535

signed short int 1 bytes same as short int

long int 4 bytes 2,147,483,647 to 2,147,483,647

signed long int 4 bytes same as long int

unsigned longint

4 bytes 0 to 4,294,967,295

FLOAT TYPE

float 4 bytes 3.4E-38 to 3.4E+38 (6 digits of precision)

double 8 bytes 1.7E-308 to 1.7E+308 (10 digits ofprecision)

long double 10 bytes 3.4E-4932 to 1.1E+4932 (10 digits of

precision)

EMPTY DATA TYPE

void

When a type modifier is used by itself, int is assumed. For example, you can specify an unsigned

integer by simply using the keyword unsigned. Thus, these declarations are equivalent.

unsigned int i; // here, int is specified

unsigned i; // here, int is implied

VARIABLES

A variable is an identifier that is used to represent some type of information within a

designated portion of the program.

Example

int a,b,c;

Here a,b,c is a variable


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RULES FOR NAMING THE VARIABLE:

Variable name can be any combination of 1 to 18 alphabets, digits or underscore First character must be an alphabet Length of the variable cant exceed upto 8 characters long, and some C compilers

can be recognizing upto 31 characters long.

No commas or blank spaces are allowed within a variable name. No special symbol, an underscore can be used in a variable name.

Syntax:

datatype v1, v2, v3,., vn;

Where

datatype is the type of the datav1, v2, v3... vn are the list of variables

Example:

main()

{

int i,j; //These 3 lines declare 4 variable

char c;

float x;

//rest of program follows

}

USER DEFINED VARIABLES:

a) Type declaration: C Language provides a feature to declare a variable of the typeof user defined type declaration, which allows users to define an identifier that would

represents an existing data type and this can be used to declare variables.

Syntax:

Where

typedef user defined type declaration

datatype existing data type

typedef datatype identifier;


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identifier refers to the new name given to the data

type

Eg: typedef int marks;

marks m1, m2, m3;

b) Enumerated data type: C language provides another user defined data type iscalled enumerated data type.

Syntax:

where

enum

user defined enumerated data type.identifier refers to the new name given to the datatype

value1, value2, , value nenumeration constants

Eg:

enum day {mon, tue, wed,,sun};

enum day w_st, w_end;

w_st = mon;

w_end=sun;

CONSTANTS

The items whose values cant be changed during the execution of program are called

constants. C constants can be classified as follows:

enum identifier {value 1, value2, ., value n};


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INTEGER CONSTANTS

An integer constant formed with the sequence of digits. There are three types of integer

constants which are different number system.

Decimal number 0 to 9

Octal number 0 to 7

Hexadecimal 0 to 9, A, B, C, D, E, F

Eg:

marks = 90;

per = 75;

discount = 15;

These are basically three types of integer namely,

Decimal Eg: 10, 153, -342, 089, etc.Octal Eg: 037, 0,0567, etc.Hexadecimal Eg: 0x4, 0x8F, 0xBCF etc.

Constants

Numeric

Integer Real

Character

Character String


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REAL CONSTANTS

It is made up of a sequence of numeric digits with presence of decimal point.

Eg:

weight = 56.8;

height = 5.6;speed = 3.11;

CHARACTER CONSTANTS

The character constant contains is a character with enclosed quotes

Eg: p N 4 +

STRING CONSTANTS

A string constant is a sequence of characters enclosed in double quotes ( ), the

characters may be letters, numbers, special characters and blank spaces etc. At the end of

string \0 is automatically placed.

Eg: String, HI39.56,

22

i) Declaring a variable as constant:When the value of some of the variables may remain constantly during the

execution of the program, in such a situation, this can be done by using the

keyword const.

Syntax:

Where

const keyword to declare constant

variable name of the variable

datatype type of the data

constant constant

Eg:

const int rate = 397;

const datatype variable =


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STRING:

String is a collection of character

Eg:India, Tamilnadu

OPERATORS:

An operator is a symbol that tells the computer to perform the certain mathematical or

logical manipulations C operators can be classified into a number of categories. They include

1. ARITHMETIC OPERATOR

C provides the entire basic arithmetic operator+ Addition operator

- Subtraction operator

/ Division operator

% modulo division

Modulo operator cant used to floating point data

Operators

Arithmetic operator

Relational operator

Logical operator

Assignment operator

Increment and decrement operator

Conditional operator

Bitwise operator

Special operator


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Example:

a=10, b=5

a+b=15

a-b=5

a/b=2

a%b=2

2. RELATIONAL OPERATOR

Relational operator which is used to compare two quantities and depending on their

relation take certain decisions

Relational expressions are used in decision statements such as if and while

They operator are

< less than

> greater than

= greater than or equal to

== is equal to

!= not equal to

Example:

a=10, b=5

ab true

a=b true

a==b false

a!=b true

3. LOGICAL OPERATOR

Logical operator which is used to test more than one condition and make decisions


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&& ->Logical AND

||->Logical OR

!->Logical NOT

Example:

if((ad))

{

printf( This is true);

}

The variable a must be less than b and, at the same time, c must be greater than d .if both

condition is true then if block statement execute, either one or false statement not execute

If((ad))

{

printf( This is true);

}

The variable a must be less than b and, at the same time, c must be greater than d .if both

condition either one or true or both true then if statement block execute

If(!(aassignment operator

Example:

Variable operator = expression

a=10, b=5

a=a+b ->a=15 is equal to a+=b ->a=15

5. INCREMENT AND DECREMENT OPERATOR

The operator ++ add 1 to operand while subtract 1.

Increment and decrement statements in for and while loops extensively


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15 # 55Two types

Prefix:A prefix operator first adds 1 or subtract to the operand and then the result is assigned to

the variable on left

Example:

Assume a=5;

b=++a;

a=6,b=6

b=--a;

a=5,b=5;

Postfix: A postfix operator first operator first assigns the value to the variable on left and then

increment or decrement the operand

Example:

Assume a=5;

b=a++

b=5,a=6

b=a- -

b=5,a=4

6. CONDITIONAL OPERATOR

Conditional operator also called as ternary operator. This conditional operator is used to

replace ifelse logic in some situation

The conditional operators are

Conditional exp? expression1: expression 2;

If the condition exp is true is expression 1 is execute .if the condition exp is false then

expression 2 is execute

a>b?(ans=10);(ans=25);

is equal to

if(a>b)

{

ans=10;

}

else


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16 # 55{

ans=25;

}

7. BITWISE OPERATOR

Bitwise operator for manipulation of data at bit level. These operator are used for testing

the bits or shifting them right or left .bitwise operator not be applied to float or double

The bitwise operators are

& Bitwise AND

| Bitwise OR

^ Bitwise Exclusive OR

> Shift right

Eg:

24 >> 2 is 6

24 0001 1000

After shifting right by 2 position,

0000 0110 6

8. SPECIAL OPERATOR

Comma operator:

The comma operator can be used to link the related expressions together .the comma

linked list of expressions are evaluated left to right and the value of right most expression is the

value combined

Example:

Value=(x=10,y=5,x+y);

Sizeof() operator:

The sizeof is compile time operator and when used with an operand it returns the number

of bytes the operand occupies. The operand may be variable, a constant or a data type qualifier

a=sizeof(sum);

b=sizeof(long int);

c=sizeof(234);


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SPECIAL SYMBOLS:

These are the symbols, which has some syntactic meaning and has got significance.

These will not specify any operation. In C language call it as Delimiters as given below:

SYMBOLS NAME MEANING

# Hash Pre-Processor directive

, comma Variable delimiters to separatelist of variables

: Colon Label Delimiters

; Semicolon Statement Delimiters

() Paranthesis Used in expressions or infunctions

{ } Curly braces using for blocking Cstructure

[] Square braces used along with arrays

EXPRESSIONS

An expression consists of a sequence of constants, identifiers, and operators that the

program evaluates by performing the operations indicated. The expression's purpose in the

program may be to obtain the resulting value, or to produce side effects of the evaluation, or

both.

Single constant, a string literal, or the identifier of an object or function is in itself an

expression. Such a simple expression, or a more complex expression enclosed in parentheses, is

called a primary expression.

Every expression has a type. An expression's type is the type of the value that results

when the expression is evaluated. If the expression yields no value, it has the type void. Some

simple examples of expressions are listed below:

Variable = Expression;

Eg:

y = (a/b) +c;

k = ((2 * x * x)/b) c;


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OPERATOR PRECEDENCE AND ASSOCIATIVITY

An expression may contain several operators. In this case, the precedence of the

operators determines which part of the expression is treated as the operand of each operator. For

example, in keeping with the customary rules of arithmetic, the operators *, /, and % have higher

precedence in an expression than the operators + and -. For example, the following expression:

a - b * c

is equivalent to a - (b * c). If you intend the operands to be grouped differently, you must use

parentheses, thus:

(a - b) * c

If two operators in an expression have the same precedence, then their associativity

determines whether they are grouped with operands in order from left to right, or from right to

left. For example, arithmetic operators are associated with operands from left to right, and

assignment operators from right to left, as shown below lists the precedence and associativity of

all the C operators.

OPERATOR GROUPING

EXPRESSION ASSOCIATIVITY EFFECTIVE GROUPING

a / b % c Left to right (a / b) % c

a = b = c Right to left a = (b = c)


PRECEDENCE OPERATORS ASSOCIATIVITY

1. Postfix operators :

[ ] ( ) . -> ++ --

(type name){list}

Left to right

2. Unary operators:

++ --

! ~ + - * & sizeof

Right to left

3. The cast operator: (type name) Right to left

4. Multiplicative operators: * / % Left to right

5. Additive operators: + - Left to right

6. Shift operators: > Left to right


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PRECEDENCE OPERATORS ASSOCIATIVITY

7. Relational operators: < >= Left to right

8. Equality operators: == != Left to right

9. Bitwise AND: & Left to right

10. Bitwise exclusive OR: ^ Left to right

11. Bitwise OR: | Left to right

12. Logical AND: && Left to right

13. Logical OR: || Left to right

14. The conditional operator: ? : Right to left

15. Assignment operators:

= += -= *= /= %= &= ^= |= =

Right to left

16. The comma operator: , Left to right

DATA INPUT AND OUTPUT

Standard devices

C always assumes that input comes from stdin or the standard input device .this is

usually the keyboard. C assumes that all output goes to stdout or the standard output device

Standard I/O devise in C

I/O DEVICE C NAME

Screen Stdout

Keyboard Stdin

Printer Stdprn

Serial port Stdaux

Error messages Stderr

Disk files None


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SIMPLE INPUT AND OUTPUT STATEMENT

scanf

The scanf () functions is used to read the formatted data items from the keyboard the

format is user defined data items .it can be read or written as defined by a programmer

The general format

scanf(control string ,argument list);

The control string is a specified format code to read from the keyboard and the

argument list is a user defined variable list .usually, the argument list of the user defined

variables must include the address operator(&) as a prefix to the variable

For example

int x,y;

scanf(%d%d,&x,&y);

char c,i;

scanf(%f%f,&c,&i);

The complete format code used in the scanf() function for the various data variables shown

below

Code Meaning

%c Read a single character

%d Read a decimal integer

%i Read a decimal integer

%e Read a floating point number

%f Read a floating point number

%h Read a short integer

%o Read a octal number

%s Read a string

%x Read a hexadecimal number

All the variables used to receive values through scanf() must be passed by their addresses .this

means that all arguments must be pointed to the variables used as arguments


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21 # 55printf()

The printf() function is one of the most important and useful function to display the

formatted output data items on the standard output device normally the video screen

The general form ofprintf() function is as

printf(control strings,argument list);

Where the control strings are user defined format code and the argument list is a set of data itemsto be displayed in a proper format as defined by the control stings

The complete format code used in the printf() function for the various data variables shown

below

Code Meaning

%c Read a single character

%d Read a decimal integer

%i Read a decimal integer

%e Read a floating point number

%f Read a floating point number

%h Read a short integer

%o Read a octal number

%s Read a string

%x Read a hexadecimal number

%% Print a percent sign

THE get() AND putc() FUNCTIONS

The most fundamental character I/O functions are getc() and putc().

getc()

The getc() function inputs a single character form the standard input device which is

keyboard ,unless you redirect it

The format for getc( ) follows

intvar=getc(device);


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22 # 55Dont let the integer intvar confuse you. Even though getc() is a character function, you use a

integer variable to store the getc() input value. getc() returns a 1 when an end-of-file condition

occurs. If you are using getc() to read information from a disk file, the 1 is read when the end of

the file is reached

The getc() device can be any c standard input device .if you are getting character input from the

keyboard ,use stdin as the device

putc()

The putc() functions writes a single character to the standard output device ,which is the

screen, unless you redirect it from your operating system.

The format ofputc() follows:

putc(intval,device);

The intval can be integer variable, expression, or constant. You output character data with

putc().the device can be any standard output c device.to write a character to your printer, use

stdprn for the device.

Example program

/*Introduces getc() and putc()*/

#include

#include

void main()

{

int inchar; //Holds incomming initial

char first,last; //Holds converted first and last intial

clrscr();

printf("what is your first name initial?");

inchar=getc(stdin); //Wait for first initial

first=inchar;

inchar=getc(stdin); // ignore newline

printf("what is your last name initial?");

inchar=getc(stdin); //Wait for last initial

last=inchar;

inchar=getc(stdin); // ignore newline


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23 # 55printf("\nHere they are!!!\n");

putc(first,stdout);

putc('\n',stdout); // A newline is output

putc(last,stdout);

getch();

}

OUTPUT

The getchar() and putchar() functions

When you perform character I/O ,the getchar() functions are easier to use than getc() and

putc(). The getchar() and putchar() functions are identical to getc() and putc(),except you do

not specify a because they assume that the standard input and output devices are stdin andstdout (typically ,the screen and the keybord).in the following

inchar=getc(stdin);

Is identical to

inchar=getchar();

And


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is identical to

putchar(var);

The getchar() and the getc() functions are both buffered input functions. That is as you

type characters, the data goes to a buffer rather than immediately to your program. The buffer is

a section of memory managed by C

When your program gets to a getc() or a getchar(),the program temporarily waits as you type the

input. The program does not seethe characters because they are going to the buffer in memory

there is no limit to the size of the buffer; it keeps filling up with you press enter. Pressing the

enter key signals the computer to release the buffer to your program

/*Illustrates simple getchar() and putchar()*/

#include

#include

void main()

{

int mychar; // Must be integer

clrscr();

mychar=getchar(); // Get the character

printf("You Typed This!!!\n");

putchar(mychar);

getch();

}


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OUTPUT

getch() and putch() funtoins

The getch() and putch() functions are slightly different than the previous character I/O

functions. Their formats are similar to getchar() and putchar() ; they both assume that stdin and

stdout are the standard input and output devices, and you cant specify other devices(unless you

redirect them with your operating system)

The format ofgetch()

intvar=getch();

The format ofputch()

putch(intvar);

The getch() and putch() functions are not ANSI C standard functions, but they are

available on a large number of compilers and well worth mentioning, getch() and putch() are

non-buffered functions

Both getch() and putch() assume that stdin and stdout are the standard input and output devices.When you want your program to respond immediately to keyboard input use getch().some

programmers want to make users press enter after answering a prompt or selecting from a menu.

They feel that buffered input gives users more time to decide if they really want to give that

answer: users can press Backspace and correct the input before pressing Enter

Example program

/*uses getch() and putch() input and output */

#include

#include


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26 # 55void main()

{

int ctr; // The for loop counter

char letters[5]; // Holds five input characters

clrscr();

printf("Please Type Five Letters....\n");

for(ctr=0;ctr


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OUTPUT

STRING I/O FUNCTIONS

The input and output functions are listed fellow

gets(s):stores input from stdin(usually directed to the keyboard)into the string named s

puts(s):output the s string to stdout(usually directed to the screen by the operating system)

Therefore when you enter stings with gets(), C places a string-terminating character in

the string at the point where you press Enter. This creates the input sting. (Without the null zero,

the input would not be a string).when you output a string, the null zero at the end of the sting

becomes a newline character. This is good because you typically prefer a newline at the end of a

line of output (to put the cursor on the next line)

Example Program

/*using gets() and puts()*/

#include

#include

void main()

{

char book[30]; // Holds the string

clrscr();

printf("What is the Book Tittle?\n");


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28 # 55gets(book); // Get an input String

printf("You Typed the Book Tittles are!\n");

puts(book); // Display the String

printf("Thanks for the Book!!!\n");

getch();

}

OUTPUT


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DECISION MAKING AND BRANCH STATEMENTS

Simple if statements:

Syntax:

if(test expression)

{

Statementblock one or more;

}

Statement x;

If the test expression is true then the statement is executes otherwise it goes to out of branch

Decision Makingand Branching

Statements

Simple ifstatements

The if elsestatements

Nesting of if elsestatements

The else if Ladder

Condition

True Statements

False

True


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30 # 55Example:

//simple if program

#include

#include

void main()

{

int age=21; //declare and assign age as 21

clrscr();

printf(\n What is student age? );

scanf(%d,&age);

if(age


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31 # 55Simple if else statements:

Syntax:

if(condition)

{

Block of one or more statements

}

else

{

Block of one or more statements

}

The if condition is true then execute entire if block statement other wise else statement is execute

Condition

True Statements False Statements

FalseTrue


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32 # 55Example:

//simple if else program

#include

#include

void main()

{

int num;

clrscr();

printf("What is your number?");

scanf("%d",&num);

if(num>=10)

{

printf("More than 10\n");

}

else

{

printf("Less or equal to 10\n");

}

getch();

}


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OUTPUT

Nested if else statements:

When a series of decisions are involved. We may have to use more than one if.else

statements

Syntax:

if(test condition-1)

{

if(test condition-2)

{

Statements -1;

}

else

{

statements -2;

}

}

else


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34 # 55{

Statements-3;

}

Statementsx;

If the condition-1 is false, the statement-3 will be executed, otherwise to perform the

second test. if the condition -2 is true, the statement-1 will be evaluated, otherwise the statement-

2 will be evaluated and then the control is transferred to the statement-x


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35 # 55

Example:

//nested if else program

#include

#include

void main()

{

int a,b,c;

clrscr();

printf("\nEnter the three valus:");

scanf("%d%d%d",&a,&b,&c);

prtinf(\n***OUTPUT***\n);

printf("The Largest values are:");

if(a>b)

{

if(a>c)

{

printf("%d",a);

}

else

{

printf("%d",c);

}

}

else

{

if(c>b)

{

printf("%d",c);

}

else

{


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36 # 55printf("%d",b);

}

}

getch();

}

OUTPUT

The else if ladder statements:

A multiple decision is a chain of if is which statement associated with each else is an if

Syntax:

If(condition)

Statement -1;

else if (condition 2)

statement-2;

else if(condition-3)

statement-3;

else if(conditionn)

statementn;

else

default statements;


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37 # 55statementx;

The conditions are evaluated from the top to downwards. As soon as a true condition is

found, the statement associated with it is executed and the control is transferred to the statement-

x. When all the condition is false then the final else containing the default statement will be

executed

Example:

//else if ladder

#include

#include

void main()

{

int num;

clrscr();

printf("Enter the Number(1-5)");

scanf("%d",&num);

printf(\n***OUTPUT***\n);

if(num==1)

printf("color=RED");

else if(num==2)

printf("color=GREEN");

else if(num==3)

printf("color=WHITE");

else if(num==4)

printf("color=YELLOW");

else if(num==5)

printf("color=BLUE");

else

printf("color=BLOCK");

getch();

}


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38 # 55

OUTPUT

switch case statement:

The switch statement is sometimes called the multiple choice statement

Syntax:

switch (expression)

{

case value1:

block-1;

break;

case value2:

block-2;

break;

.

.

.

default:

default-block;

break;

case 2

Statements

case 1

Statements

default

Statements

switch


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39 # 55

The expression can be an integer expression, a character, a constant or a variable. The sub

expression (value1, value 2 and so on)

If the expression matches value1 the statement execute and so on. None of the value is

not match then default statement is executes

Example:

//simple switch program

#include

#include

void main()

{

int num;

clrscr();

printf("Enter the number(1-7)");

scanf("%d",&num);

switch(num)

{

case 1:

{

printf("This is Sunday");

break;

}

case 2:

{

printf("This is Monday");

break;

}

case 3:

{

printf("This is Tuesday");

break;

}


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40 # 55case 4:

{

printf("This is Wendsday");

break;

}

case 5:

{

printf("This is Thursday");

break;

}

case 6:

{

printf("This is Friday");

break;

}

case 7:

{

printf("This is Saturday");

break;

}

default:

printf("You Enter the Wrong Number try again");

}

getch();

}


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41 # 55

OUTPUT

UNCONDITIONAL STATEMENTS

break

The for loop was designed to execute for a specified number of times, sometimes, though

rarely the for loop should quit before the counting variable has reached its final value, as withwhile loops, you use the break statements to quite a for loop early.

The break statement goes in the body of the for loop. Programmers rarely put break on a line byitself, and it almost comes after an if test.if the break were on a line by itself the loop would

always quit early defeating the purpose of the for loop

The format of break is

break;

Example

for(ctr=0;ctr


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42 # 55Example

/*a for loop running at the user's request*/

#include

#include

void main()

{

int num,ans; // loop counter variable

clrscr();

printf(" Here are the numbers from 1 to 20\n");

for(num=1;num


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44 # 55continue; // Causes body to end early

printf("C Programming\n");

}

getch();

}

OUTPUT

GOTO STATEMENT:

C supports the goto statement to branch unconditionally from one point to another in the

program. The goto requires a label to identify the place where the branch is to be made. A label

is any valid variable name, must be followed by a colon. The label is placed immediately before

the statement where the control is to be transferred.

General forms:

Forward jump Backward jump

Syntax:

goto begin;

goto label;

..

..

label:

statement;

label:

statement;

..

..

goto label;


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45 # 55goto breaks the normal sequential execution of the program. If the label: is before the

statement goto label; a loop will be formed and some statements will be executed repeatedly.

such a jump is called backward jump. If the label: is placed after the goto label; some statements

will be skipped and the jump is known as forward jump. A goto is used at the end of a program

to direct the control to go to the input statement, to read further data.

Example

/* This is Program demonstrates the overuse of goto */

#include

#include

void main()

{

clrscr();

goto Here;

First:printf("A\n");

goto Final;

There:

printf("B\n");

goto First;

Here:

printf("C\n");

goto There;

Final:

getch();

}


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46 # 55OUTPUT

DECISION MAKING AND LOOP STATEMENTS

while

The while statement is one of several C construct statement. Looping statements cause

parts of a program to execute repeatedly as long as a certain condition is being met. While is an

entry-controlled loop statement.

Syntax:

while(test-condition)

{

Body of the loop

}

The test condition is evaluated and if the condition is true(non zero),the block of one or

more C statements execute repeatedly until the test condition becomes false(evaluates to zero)

DECISIONMAKING AND

LOOPSTATEMENTS

while do-while for


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47 # 55

Example:

//simple while program

#include

#include

void main()

{

char name[15];

int count=0;

clrscr();

printf("What is Your First Name?");

scanf("%s",name);

while(name[count])

{

count++;

}

printf(\n***OUTPUT***\n);

printf("Your Name has %d Characters",count);

getch();

}

Condition

Body of the loop

False

True


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50 # 55

Example:

//simple for program

#include

#include

void main()

{

int total,ctr;

total=0;

clrscr();

for(ctr=100;ctr


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51 # 55

OUTPUT

NESTED LOOPS:

One for loop statement within another for loop statement called nested for loop.

Syntax:

for ()

{

.

for (..)

{

.

}

}

Example:

#include

#include

void main()

{

int i,j;

clrscr();for(i=1;i


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52 # 55{

for(j=1;j


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53 # 55

Example:

a) while () b) do{ {

if (condition) .

break; .

Exit if (condition

From Exit break;

loop } from }while (.);

loop

c) for () d) for ()

{ {

. .

. for (..)

if (error) {

break; ..

Exit .. if (condition)

from .. break;

loop Exit from .

} Inner loop }

.............. .

}

Skipping a part of loop:During the loop operations, to skip a body of loop under some conditions we may

use continue statement. It tells the compile to skip the following statement and then continues

with the next iteration.


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54 # 55Example:

a) while (test-condition) b) do{ {

-------------- ---------------

if (-----------) if (-----------)

continue; continue;

----------- -----------

----------- -----------

} }while(test-condition);

c) for (initialization; test condition; increment/decrement operator)

{

------------

if -----------)

continue;

--------------

--------------

}

THE STANDARD HEADERS

Each standard library function is declared in one or more of the standard headers. These

headers also contain all the macro and type definitions that the C standard provides. This chapter

describes the contents and use of the standard headers.

Each of the standard headers contains a set of related function declarations, macros, and type

definitions. The standard headers are also called header files, as the contents of each header are

Usually stored in a file. Strictly speaking, however, the standard does not require the headers to

be organized in files.


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unit 1for civil

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