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C Programming Basics

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Structure of C Language

1. Documetation Section [optional]

/*------------*/

2. Link Section

#include

3. Definition of constants [optional]#define variable value

4. Global variable declaration [optional] datatype variable

5. main()

{ declaration;executable statements; }

6. Sub functions

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Data types

The following are the datatypes available in c-Language.

* Primary Datatypes

* Derived Datatypes

* User defined Datatypes

Derived Datatypes - Arrays, stringsUser defined Datatypes - structures, unions

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Primary Datatypes

Type Size in bits Range

char 8[1 byte] -128 to 127

Unsigned char 8[1 byte] 0 to 255

signed char 8[1 byte] -128 to 127

int 16[2 bytes] -32,768 to 32,767Unsigned short int 8[1byte] 0 to 65,535

signed short int 8[1 byte] 0 to 65,535

long int 32[4 bytes] -2,147,483,647 to 2,147,483,646

signed long int 32[4 bytes] -2,147,483,647 to 2,147,483,646

unsigned long int 32[4 bytes] 0 to 4,294,967,295

float 32[4 bytes] 6 digits of precisiondouble 64[8 bytes] 10 digits of precision

long double 128[16 bytes] 10 digits of precision

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# include

# include

Void main(){

Int a=32769;

Printf(%d,a);----------------- -32767}

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# include

# include

Void main(){

Unsigned Int a=32769;

Printf(%d,a);}

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Derived Datatypes - Arrays,

strings

User defined Datatypes structures,

unions

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printf()

* Used to display the output by using

conversion specifiers

* Returns no.of characters printed on the

screen.

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prints the simple message on the

screen

#include

main()

{ printf("Welcome to c world"); }

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#include

main()

{int i;

i=printf("welcome%d",i);

printf(%d",i);}

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Output

Welcome 7

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B

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scanf() used to read the data from the input

device (keyboard).

scanf() Returns no.of inputs taken from the

keyboard

syntax: scanf("conversion specifier",variable);

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main()

{

int i,a,b;i=scanf(%d%d,&a,&b);

printf(%d",i);

}

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output

2

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D

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Operators in C

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Arithmetic Operators+,-,*,/,%

Logical operators

&&,||,! Relational Operators

>,=,

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Operator Precedence

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#define square(x) x*x

main()

{

int i;

i = 64/square(4);

printf("%d",i);

}

Answer --------------- 4

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1. D

2. A

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A

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B

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D

6 will be printed

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Increment Operator(++)

Pre increment

Post increment

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Decrement Operator(--)

Pre decrement

Post decrement

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B

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#include

int main()

{

int i=2;

int j=++i + ++i + i++;

printf("%d\n",i); ------------------- 5

printf("%d\n",j); ------------------ 11

}

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C

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Bitwise Operators

>> --------------- RIGHT SHIFT

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x = y / 4; same as x = y >> 2;

x = y / 32; same as x = y >> 5;

x = y * 8; x = y

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How to swap two numbers using

http://www.gamedev.net/index.php?app=core&module=attach&section=attach&attach_rel_module=ccs&attach_id=3637

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How to swap two numbers using

bitwise operators?

Program:#include

main() {

int i = 65;

int k = 120;

printf("\n value of i=%d k=%d before swapping", i, k);

i = i ^ k;

k = i ^ k;

i = i ^ k;

printf("\n value of i=%d k=%d after swapping", i, k);}

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Explanation:

i = 65; binary equivalent of 65 is 0100 0001

k = 120; binary equivalent of 120 is 0111 1000

i = i^k;

i...0100 0001

k...0111 1000

---------

val of i = 0011 1001

---------

k = i^k

i...0011 1001k...0111 1000

---------

val of k = 0100 0001 binary equivalent of this is 65

---------(that is the initial value of i)

i = i^k

i...0011 1001

k...0100 0001

---------

val of i = 0111 1000 binary equivalent of this is 120

---------(that is the initial value of k)

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Write a program to swap two

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Write a program to swap twonumbers without using a temporary

variable. Program:

#include

main() {

int a, b;

printf("Enter values of a and b: \n"); scanf("%d %d", &a, &b);

printf("Before swapping a=%d, b=%d", a,b n);

/*Swapping logic */

a = a + b;

b = a - b; a = a - b;

printf("After swapping a=%d b=%d", a, b);

}

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Int k= printf("Hello World"))

Printf(%d,k);

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Answer : 11

Length of the hello world is 11.

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Eg1: 14

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Program: Program to illustrate left shift and rightshift operations.

#include

int main(void)

{

int x=10,y=10;

printf("left shift of 10 is %d \n",x1); return 0;

}

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Output:

left shift of 10 is 20

right shift of 10 is 5

Explanation:

Left shift (by 1 position) multiplies a number

by two. Right shift divides a number by 2.

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A

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Control Structures

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No Error

Case statements

accepts expressions

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D

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D

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A

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NO ERROR

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D

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Arrays

Variables

Arrays

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C

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D

Val[0][3]

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A

C

B

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12345678901234567890123456789012345678901234567890

--------------------------------------------------hello ####### %10s

hello ####### %-10s

00064 ####### %05d

64 ####### %5d

64 ####### %-5d

100 ####### %5o

64.00 ####### %5.2f

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A

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c

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B

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Functions

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C

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B

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C

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USER DEFINED FUNCTION

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Pointers

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C

B

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B

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1200 10

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1

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B

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NO

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NO. SINCE ARITHMATIC OPERATION IS NOT ALLOWED ON VOID POINTER

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D

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A

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D

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A

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C

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A

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C

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A,B

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C

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A

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A,C

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A,B,C

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D

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A,C,D

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C

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C

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FILES

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FILE IS A DATA TYPE

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FILE *fopen(const char *filename, const char*mode);

Used to open a file and returns the starting

address Returns NULL if file cant be opened

int fclose(FILE *stream); Used to close the file

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int fprintf(FILE *stream, const char *format,...);

This acts exactly like printfexcept that the data is

written to stream, rather than stdout. It normallyreturns the number of characters written, or a

negative value for an error. Int

Used to store the data.

fprintf(fp,formatspecifiers,variables);

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http://personal.ee.surrey.ac.uk/Personal/R.Bowden/C/printf.htmlhttp://personal.ee.surrey.ac.uk/Personal/R.Bowden/C/printf.html

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fscanf(FILE *stream, const char *format, ...);

This acts exactly like scanfexcept that the data

is read from stream, rather than stdin. It

normally returns the number of input itemsconverted and assigned, or EOF for an error.

Used to get the data.

fscantf(fp,formatspecifiers,variables with &symbol);

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To read the character by character

http://personal.ee.surrey.ac.uk/Personal/R.Bowden/C/scanf.htmlhttp://personal.ee.surrey.ac.uk/Personal/R.Bowden/C/scanf.html

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To read the character by character

Char Getc(filepointer)

Char fgetc(filepointer);

Used to read the character from the file

Returns EOF at the end.

Both are same, but fgetc returns EOF when any

error or EOF is reached.

Putc(filepointer,char); Used to store the character into file.

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Fgets()

Used to read the string by string from file

Fgets(variable, length,filepointer)

It also returns EOF when reached to end

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How can we read/write structures from/todata files?

By using fread() and fwrite() functions one

can read or write data to data files.

Fread(&emp,sizeof(emp),1,filepointer)

Fwrite(&emp,sizeof(emp),1,filepointer)

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Fseek()

Used to position the file pointer

Fseek(fp,negitive/positivenumber,location);

Location may be 0 if it is beginning of the file(SEEK_SET)

1 if it is from the current position ( SEEK_CUR)

2 if it is from the current position ( SEEK_END)

Negitive number indicates backward direction and

positive indicates forward direction

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B,C

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B,C,D

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B,D

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A,B

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A,B,C

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A

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C