want to learn files,then just use this ppt to learn

good ppt for files learning

1. FILES

2. Introduction to Files So far, the operations using C program are done on a prompt / terminal which is not stored anywhere. But in the software industry, most of the programs are written to store the information fetched from the program. One such way is to store the fetched information in a file. Different operations that can be performed on a file are: Creation of a new file Opening an existing file Reading from file Writing to a file Move the pointer to a specific location in a file Closing a file

3. What is a File? A file can be treated as external storage. It consists of a sequence of bytes residing on the disk. A program can create, read, and write into a file. Unlike an array, the data in the file is retained even after the program finishes its execution. It's a permanent storage medium. File handling in C programming uses FILE STREAM as a means of communication between programs and data files. The INPUT STREAM extracts the data from the files and supplies it to the program. The OUTPUT STREAM stores the data into the file supplied by the program. C uses a structure called FILE (defined in stdio.h ) to store the attributes of a file.

4. Declaring a File Pointer In C language, in order to declare a file, we use a file pointer. A file pointer is a pointer variable that specifies the next byte to be read or written to. Every time a file is opened, the file pointer points to the beginning of the file. A file is declared as follows: FILE * fp ; // fp is the name of the file pointer

5. The basic File operations Open a file Read data from a file Write data into a file Close a file

6. Library Functions for FILE handling No. Function Description 1 fopen() opens new or existing file 2 fprintf () write data into the file 3 fscanf() reads data from the file 4 fputc() writes a character into the file 5 fgetc() reads a character from file 6 fclose() closes the file 7 fseek() sets the file pointer to given position 8 fputw() writes an integer to file 9 fgetw() reads an integer from file 10 ftell() returns current position 11 rewind() sets the file pointer to the beginning of the file

7. Opening File: fopen () The fopen () function is used to open a file. The syntax of the fopen () is given below. fp = FILE * fopen ( const char *filename, const char *mode); fp is the file pointer that holds the reference to the file, the  filename  is the name of the file to be opened or created, and  mode  specifies the purpose of opening a file such as for reading or writing. FILE is an object type used for storing information about the file stream.

8. Opening File: fopen () A file can be opened in different modes. Below are some of the most commonly used modes for opening or creating a file. Mode Description r opens a text file in read mode w opens a text file in write mode a opens a text file in append mode r+ opens a text file in read and write mode w+ opens a text file in read and write mode a+ opens a text file in read and write mode rb opens a binary file in read mode wb opens a binary file in write mode ab opens a binary file in append mode rb + opens a binary file in read and write mode wb + opens a binary file in read and write mode ab+ opens a binary file in read and write mode

9. #include<stdio.h>   void  main( )   {   FILE  * fp  ;   char   ch  ;   fp  =  fopen (" file_handle.c","r ") ;   while  ( 1 )   {   ch  =  fgetc  (  fp  ) ;   if  (  ch  == EOF )   break  ;   printf ("%c", ch ) ;   }   fclose  ( fp  ) ;   } Opening File: fopen ()

10. A file needs to be closed after a read or write operation to release the memory allocated by the program. In C, a file is closed using the  fclose ()  function. This returns 0 on success and EOF in the case of a failure. An EOF is defined in the library called stdio.h . EOF is a constant defined as a negative integer value which denotes that the end of the file has reached. Syntax: fclose ( FILE * fp ); Closing File: fclose ()

11. Writing and Reading Functions getc (): Read a single character from the opened file putc (): Write a single character from the opened file fgetc (): Reads a character from the file with the help of the file pointer  fp . It returns EOF at the end of the file fputc (): W rites a character into the file with the help of the file pointer  fp . It returns EOF in the case of an error fgets (): Read a line of message from the file. fputs (): Write’s a line of message into the file. fprintf (): It sends formatted output to a stream. fscanf (): It reads formatted data from the stream. putw (): Write’s an integer data into a file. getw (): Read integer data from the file.

12. getc (): Read a single character getc (): This function reads a single character from the opened file and moves the file pointer. It returns EOF if end of file reached. Syntax: char ch = getc ( fp ); It is available in conio.h

13. #include<stdio.h> #include<conio.h> void main() { FILE *f; char c; f = fopen (“list.txt”, “r”); if(f == NULL) ptintf (“File not find”); else while(c = getc (f)) != EOF) printf (“% c”,c ); fclose (f); } getc (): Example

14. putc (): Write a single character putc (): This function is used to write a single character into a file. If an error occurs it returns EOF. Syntax: putc ( ch , Fp ); ‘ Fp ’ indicates File pointer.

15. #include<stdio.h> #include<conio.h> void main() { FILE *f; char c; ptintf (“Enter few words and ‘*’ to exit”); f = fopen (“words.txt”, “w”); while( (c = getchar ()) != ‘*’ ) putc (c , f); fclose (f); } put c (): Example

16. fputc (): Write a single character fputc (): This function writes a character c into the file with the help of the file pointer fp. It returns EOF in the case of an error. Syntax: int fputc ( int c, FILE * fp );

17. #include<stdio.h> #include<conio.h> void main() { FILE * fp ; fp = fopen ("file1.txt", "w");//opening file fputc ('a', fp );//writing single character into file fclose ( fp ); } fput c (): Example

18. fgetc (): Read a single character fgetc (): The fgetc () function returns a single character from the file. It gets a character from the stream. It returns EOF at the end of file. Syntax: int fgetc (FILE * fp )

19. #include<stdio.h> #include<conio.h> void main() { FILE * fp ; char c; fp = fopen (" myfile.txt","r "); while((c= fgetc ( fp ))!=EOF) printf ("% c",c ); fclose ( fp ); } fget c (): Example

20. fputs () and fgets () The fputs () and fgets () in C programming are used to write and read string from stream fputs (): The fputs () function writes a line of characters into file. It outputs string to a stream. Syntax: int fputs ( const char *s, FILE * fp ); This function writes string s to the file with the help of the reference pointer fp.

21. #include<stdio.h> #include<conio.h> void main() { FILE * fp ; fp = fopen ("myfile2.txt","w"); fputs ("hello c programming", fp ); fclose ( fp ); } fputs (): Example

22. fputs () and fgets () fgets (): The fgets () function reads a line of characters from file. It gets string from a stream. Syntax: char * fgets ( char *buffer, int n, FILE * fp ); fgets () reads up to n characters from the input stream referenced by fp. The string reads and copied into the character buffer and terminates when a null character is encountered.

23. #include<stdio.h> #include<conio.h> void main() { FILE * fp ; char text[300]; fp = fopen ("myfile2.txt","r"); printf ("%s", fgets (text,200,fp)); fclose ( fp ); } fgets (): Example

24. fprintf () and fscanf () fprintf (): The fprintf () function is used to write set of characters into file. It sends formatted output to a stream. Syntax: int fprintf (FILE * fp , const char *format)

25. #include<stdio.h> #include<conio.h> void main() { FILE * fp ; fp = fopen ("file.txt", "w");//opening file fprintf ( fp , "Hello file by fprintf ...\n");//writing data into file fclose ( fp ); } fprintf (): Example

26. fprintf () and fscanf () fscanf (): The fscanf () function is used to read set of characters from file. It reads a word from the file and returns EOF at the end of file. Syntax: int fscanf (FILE * fp , const char *format , ..)

27. #include<stdio.h> #include<conio.h> void main() { FILE * fp ; char buff[255];//creating char array to store data of file fp = fopen ("file.txt", "r"); while( fscanf ( fp , "%s", buff)!=EOF) printf ("%s ", buff ); fclose ( fp ); } fscanf (): Example

28. #include<stdio.h> #include<conio.h> void main() { FILE * fptr ; int id; char name[30]; float salary; fptr = fopen ("emp.txt", "w+"); if ( fptr == NULL) { printf ("File does not exists \n"); return 0; } fscanf (): Example

29. #include<stdio.h> #include<conio.h> void main() { FILE * fptr ; int id; char name[30]; float salary; fptr = fopen ("emp.txt", "w+"); if ( fptr == NULL) { printf ("File does not exists \n"); return 0; } Hold employee information in to a File printf ("Enter the id\n"); scanf ("%d", &id); fprintf ( fptr , "Id= %d\n", id); printf ("Enter the name \n"); scanf ("%s", name); fprintf ( fptr , "Name= %s\n", name); printf ("Enter the salary\n"); scanf ("%f", &salary); fprintf ( fptr , "Salary= %.2f\n", salary); fclose ( fptr ); }

30. getw () and putw () putw (): This function is used to write an integer value to file. This function deals with integer data only. Syntax: putw ( int v, FILE *FP); getw (): This function returns the integer value from a file and increments the file pointer. This function deals with only integers. Syntax: int getw ( FILE *FP );

31. Block Input and Output It is important to know how numerical data is stored on the disk by fprintf () function. Text and characters requires one byte for storing them with fprintf (). Similarly for storing numbers in memory two bytes and for floats four bytes. For example 3456 occupies two bytes in memory. But when it is transferred to the disk file using fprint () function it would occupies four bytes. For each character it requires one byte. Even for float also each digit including dot(.) requires one byte. Thus large amount of integers and float data requires large space on the disk. To overcome this problem files should be read and write in binary mode, for which we use fread () and fwrite () functions. fwrite (): This function is used for writing an entire structure block to a given file. fread (): This function is used for reading an entire block from a given file.

32. #include<stdio.h> #include<conio.h> void main() { struct { char name[20]; int age; }stud[50],s1[50]; FILE * fp ; int i , j=0, n; char str[15]; printf (“Enter File Name:”); scanf (“% s”,str ); fp = fopen (str, “ rb ”); if( fp == NULL) puts(“File does not exist”); Block Input and Output

33. else { puts(“How many records:”); scanf (“%d”, &n); for( i =0;i< n;i ++) { puts(“Name:” ); scanf (“%s”, &stud[ i ].name); puts(“Age:” ); scanf (“%s”, &stud[ i ].age); } j=n; while(n !=0 ) { fwrite (&stud, sizeof (stud), 1, fp ); n--; } Block Input and Output

34. for( i =0; i <j ; i ++ ) { fread (&s1, sizeof (s1), 1, fp ); printf (“Name %s \t Age %d \n”, s1[ i ].name, s1[ i ].age); } }//else close fclose ( fp ); }//main close Block Input and Output

35. fseek () function The fseek () function is used to set the file pointer to the specified offset. It is used to write data into file at desired location. Syntax: int   fseek ( FILE  *stream,  long   int  offset,  int  position)   Three are arguments are to be passed through this function. They are: File pointer Offset: offset may be positive (moving in forward from current position) or negative (moving backwards). The offset being a variable of type long. The current position of file pointer. There are 3 constants used in the fseek () function for position : SEEK_SET, SEEK_CUR and SEEK_END Integer value Constant Location in the File SEEK_SET Beginning of the file 1 SEEK_CUR Current position of the file pointer 2 SEEK_END End of the file

36. #include < stdio.h >   void  main(){       FILE  * fp ;         fp  =  fopen (" myfile.txt","w +");       fputs ("This is a C program",  fp );            fseek (  fp , 7, SEEK_SET );       fputs ("File handling in C",  fp );       fclose ( fp );   }   fseek () Example myfile.txt This is File handling in C

37. rewind() function The rewind() function sets the file pointer at the beginning of the stream. It is useful if you have to use stream many times. Syntax: void  rewind( FILE  *stream)   Example: File: file.txt this is a simple text  

38. File Name: rewind.c #include<stdio.h> void main(){ FILE * fp ; char c; fp = fopen (" file.txt","r "); while((c= fgetc ( fp ))!=EOF) printf ("% c",c ); rewind( fp );//moves the file pointer at beginning of the file while((c= fgetc ( fp ))!=EOF) printf ("% c",c ); fclose ( fp ); } rewind() Example File: file.txt this is a simple text Output: this is a simple textthis is a simple text

39. ftell () function The ftell () function returns the current file position of the specified stream. We can use ftell () function to get the total size of a file after moving file pointer at the end of file. We can use SEEK_END constant to move the file pointer at the end of file. Syntax: long int ftell (FILE *stream)

40. File Name: ftell.c #include < stdio.h > void main (){ FILE * fp ; int length; fp = fopen ("file.txt", "r"); fseek ( fp , 0, SEEK_END); length = ftell ( fp ); fclose ( fp ); printf ("Size of file: %d bytes", length); } ftell () Example File: file.txt this is a simple text Output: Size of file: 21 bytes

41. Thank you