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ICP

Lab -1 & 2


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Simplest C Program

Hash

#includemain()

{

printf( Programming in C is Interesting);

return 0;

}


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Preprocessor Directive

# include: Is a preprocessor directive whichdirects to include the designated file whichcontains the declaration of library functions(pre defined).

stdio.h (standard input output) : A header filewhich contains declaration for standard input

and output functions of the program.Like printf,scanf


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When to use preprocessor directive

When one or more library functions are used,the corresponding header file where the

information about these functions will bepresent are to be included.

When you want to make use of thefunctions(user-defined) present in a differentprogram in your new program the sourceprogram of previous function has to be

included.


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Defining main( )

When a C program is executed, system firstcalls the main( ) function, thus a C programmust always contain the function main( )somewhere.

A function definition has:

heading

{declarations ;

statements;

}


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Basic Structure of a C program

preprocessor directiveint main( )

{

declarations;

_________________;

______body_______;

_________________;

return 0;}


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Concept of Comment

Comments are inserted in program to maintainthe clarity and for future references. They helpin easy debugging.

Comments are NOT compiled, they are just forthe programmer to maintain the readability ofthe source code.

Comments are included as

/* ..

*/


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PRE DEFINED

DATA TYPES


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Data Types

Every program specifies a set of operations tobe done on some data in a particular sequence.

However, the data can be of many types suchas a number, real, character, string etc.

C supports many data types out of which the

basic types are:

int, float , double and char.


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Four Basic Data Types In C, there are 4 basic data types:

1. char,

2. int,

3. Float and

4. Double

Each one has its own properties.For

instance,they all have different sizes.

The size of a variable can be pictures as thenumber of memory slots that are required to

store it.


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Char Data type A variable of type charcan store a single

character.

All character have a numeric code associated with

them, so in reality while storing a charactervariable its numeric value gets stored.

The set of numeric code is called as ASCII,American Standard Code for Information

Interchange.


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Reading a character

Simplest of all operations is reading character

from stdin and writing to stdout

Single character can be read from getchar()

Writing a character to terminal can be done byputchar()

var_name = getchar();


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char name; //name is of character data

type

name = getchar(); // single character is read &

assignedto variable name

putchar(name); //displays character typed by

you onscreen


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Fundamental Data Types

Data type Size in bits

integer (int) 16

character (char) 8

floating point (float) 32

double 64


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Size of data types

Size of data types is compilerand processortypes dependent.

The size of data type can be determined by

using sizeof keyword specified in betweenparenthesis

For Turbo 3.0 compiler, usually in bytes

char -> 1 bytes int -> 2 bytes

float -> 4 bytes

double -> 8 bytes


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Integer Data Type

Variables of the int data type represent wholenumbers.

If at run time you try to assign a fraction to an int

variable,the decimal part is ignored and thevalue assigned is rounded down from the actual

value.

Also assigning a character constant to an int

variable at compile time assigns the ASCII value.


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Float data type

Forstoring decimal numbers float data type isused.

Floats are relatively easy to use but problemstend to occur when performing division

In general:

An int divided by an int returns an int.

An int divided by a float returns a float.A float divided by an int returns a float.

A float divided by a float returns a float.


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Char data type

Characters (char) To store a character intoa char variable,you must enclose it withSINGLE QUOTE marks i.e. by .

The double quotes are reserved for string(a

collection of character). The character that you assign are called ascharacter constants.

You can assign a char variable an integer.i.e.

its integer value.a, z , A , Z , ?, @, 0, 9

- Special Characters: preceded by\

\n, \t , \0, \, \\ etc.


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ASCII codes


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Format specifiers There are several format specifiers-The one you

use should depend on the type of the variable youwish to print out.The common ones are as follows:

Format Specifier Type

%d int%c char

%f float

%lf double%s string

To display a number in scientific notation,use %e.

To display a percentage sign,use %%


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Declaration of Variable To Declare a variable means to reserve memory

space for it.

In the declaration variable is provided a namewhich is used through out the program to refer tothat character.

Example:

char c;

OR

char c, k, l;

Declaring the characterdoes not initialize thevariable with the desired value.


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Memory view

i

c

char type

integer

Each variable has an

unique address of

memory location

associated with it


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Important about Variable

Always remember in C , a variable must always be

declared before it used.

Declaration must specify the data type of the value of

the variable.

Name of the variable should match with itsfunctionality /purpose.

Example int count ; for counting the iterations.

float per_centage ; for percentage ofstudent


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Initialization

Initializing a variable involves assigning(puttingin) a value for the first time.This is done byusing the ASSIGNMENT OPERATOR, denotedby the equals sign,=.

Declaration and initializing can be done onseparate lines, or on one line.

char c=x; or

char c;

c=x


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Printing value of char variable

printf( %c, a);

This causes the %c to be replaced by

value of character variable a.

printf(\n %c, a);

\n is a new line character which will printthe value of variable on newline.


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Identifiers and Variables Identifier: A name has to be devised for program

elements such as variables or functions.

Variable:

Variables are memory regions you can use to hold data

while your program is running.

Thus variable has an unique address in memory region.

For your convenience, you give them names (instead of

having to know the address)

Because different types of data are different sizes, thecomputer needs to know what type each variable is so it

can reserve the memory you need


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Rules for Identifiers Contains only letters, digits and under score

characters,

example amount, hit_count

Must begin with either a letter of the alphabet or anunderscore character.

Can not be same as the keywords, example it cannot be void, int.

Uppercase letters are different than lowercase,example amount, Amount and AMOUNT all threeare different identifiers.

Maximum length can be 31 characters.

Should not be the same as one already defined inthe library, example it can not be printf/scanf.

No special characters are permitted. e.g. blanks ace eriod semicolon comma etc.


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Naming Variables


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INPUT & OUTPUT

Input and Output form an important part of anyprogram.

To do anything useful your program needs to be ableto accept input data and report back your results.

In C, the standard library provides routines for inputand output. The standard library has functions for i/othat handle

input, output, and character and string manipulation.

Presently we consider, all the input functionsdescribed read from standard input and all theoutput functions described write to standard output.Standard input is usually the keyboard. Standard

output is usually the monitor.


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Display data using printf()

#include

main()

{

int age = 25;printf( %d,age);

}

output:

25


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Display data using printf()

#include

main()

{

int age = 25;printf( The age of student: %d,age);

}

output:

The age of student: 25


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printf( )

1. It is used to print message or result on the output screen.It is

define in stdio.h header file.

2. Returns the number of characters it outputs on the screen.

Example:printf( Enter the number whose multiplication table you want to

generate);

printf( Balance in your account is %d, bal); /* where bal is int

type*/

printf(Balance =%d,Total tax is %f ,bal, tax); /* where tax is

float type */


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scanf( ) scanf( ) : It is used to read data from keyboard that can be

numerical values, characters or strings.It is defined instdio.h

The function returns the number of data items that havebeen entered successfully.

Example:int num1,num2,num3;

char var;

printf( enter the numbers );

scanf(%d%d%d, &num1,&num2,&num3);printf(enter a character);

scanf(%c, &var);


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