File Processing

File Processing

File and Streams

Streams => To keep key in data from keyboard need to be saved at secondary storage device as a data file.

           => A suquence of character.

           => All input and output data is a stream.

There are 3 standard streams :

1)   Standard Input Stream : Controlling input stream for keyboard

2)   Standard Output Stream : Controlling output stream for keyboard

3)   Standard Error Stream : Controlling the error messaging

File => A collection of record

     => Record is a collection of field

     => Field is a block of byte

     => Byte is collection of bit

• TEXT FILE saved in a text format or ASCII File

– Storage size depends on its data: 10000 needs 5 byte

– Can be open using standard text editor application

– or c:>TYPE file_name

• BINARY FILE storing numerical data in affixed format in line with micro-processor format definition

(example: format sign-magnitude 2’s complement)

Buffer Area

Part of memory used as a temporary space before data moved to a file.

Syntax :

     FILE *fp;

Open File

Opening a File using fopen() :

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

fopen() : return a pointer to the start of a buffer area. Null will be returned if file unable to open.

Possible mode Value :

“r”     => opening a file to be read.

"w”    => creating a file to be written.

“a”     => opening a File for data append.

“r+”   => opening a File for read/write.

“w+”  => creating file for read/write.

“a+”   => opening a File for read/append

“rb”    => opening a File (binary) to be read.

“wb”   => creating a file (binary) for write operation

Close File

Closing a File using fclose() :

     int fclose (FILE *stream);

fclose() : will release the buffer area and immediately send the remaining data to file.

Closing a File using fcloseall() :

   int fcloseall (void);

fcloseall() : will return the number of stream closed if successful and return EOF instead.

Input & Output File

~ fgetc <input>

   - Read one character from a file

   - fgetc(stdin) = getchar()

   - Syntax : int fgetc( FILE * stream );

   - Return the character when successful and EOF while error.

 

~ fputc <ouput>

   - Writing one character to a file

   - fputc('a', stdout) similiar with putchar( 'a' )

   - Syntax : int fputc( int c, FILE*stream );

   - Return a character when successful and EOF if error

 

~ fgets <input>

    – Syntax: char *fgets( char *string, int n, FILE *stream );

    – Read one line from a file that ended with new line, or at maximum of n-1 number of character

    – Return a string if successful and NULL while error

 

~ fputs <output>

    – Writing a line to a file

    – Syntax: int fputs( const char *string, FILE *stream );

    – Return non-negative value while successful and EOF if error.

 

~fscanf  <input>

   – Syntax:  int fscanf( FILE *stream, const char *format [, argument ]... );

   – Read data from file inline with the scanf formatting.

   – Return the number of field read while successful, and EOF if error

 

~fprintf <output>

   – Syntax:  int fprintf( FILE *stream, const char *format [, argument ]...);

   – Writing data to a file using the printf format.

   – Return number of byte written if successful and negative value if error.

 

~fwrite

   – syntax: size_t fwrite( const void *buffer, size_t size, size_t count, FILE *stream );

   – Writing a block of data in the buffer area to the file

   – Return number of byte data written, and error otherwise.

 

~fread

  – Syntax: size_t fread( void *buffer, size_t size, size_t count, FILE *stream );

  – Read a block size of data from a file

 

~feof

  – Syntax : int feof( FILE *stream );

  – Finding out if the pointer has reached end-of-file

  – Return 0 if not end-of-file