C- Programming

Sujan Karki
Email: sujan@ioepc.edu.np
Contact No.: 9819387234
Master’s in Information System Engineering (MscIne) *Ongoing
Bachelor in Computer Engineering – Purwanchal Campus,IOE
 UNIT 10

Files and File Handling in C

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 File Handling
⚫ File is a collection of related data placed on the disk.
C support the concept of files through which data can
be stored on the disk or secondary storage device. The
stored data can be read whenever required.

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Opening a File
A file must be opened before any I/O operations performed on
that file. The process of establishing a connection between the
program and file is called opening the file.
A structure named FILE is defined in the file stdio.h that contains
all information about the file like name, status, buffer size,
current position, end of file status etc.

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 …
Closing of file:
The file that was opened using fopen ( ) function must be closed
when no more operations are to be performed
on it. After closing the file, connection between file and program
is broken.
Although all the files are closed automatically when the program
terminates, but sometimes it may be necessary
to close the file by using fclose( ) function.

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 Text mode
· In text mode every digit or text are stored as a character
and while reading the content back, the conversion is
required from character to appropriate format and takes lots
of space.
· Character I/O, string I/O, and formatted I/O use text mode.
· If 3.14159 is stored in character mode file size would be 8
bytes (counts each character including decimal and EOF).
Binary mode
· In binary mode every digit or text is stored in binary format
and while reading the content no conversion
is necessary and takes little space.
· fread ( ) and fwrite ( ) are used in binary mode.
· If 3.14159 is stored in character mode file size would be 4
bytes.
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 ⚫ Input/Output Functions
The functions used for file input/output are
1. Character I/O
a. fputc( )
This function writes a character to the specified file at the current
file position and then increments the file position pointer.
Syntax: fputc(character or char_variable , file_ptr_variable);
b. fgetc( )
This function reads a single character from a given file and
increments the file pointer.
Syntax: char_variable = fgetc(file_ptr_variable);
c. getc( ) and putc( )
The operation of getc( ) and putc( ) are exactly similar to that of
fgetc( ) and fputc( ) , the only difference is that the former two are
defined as macros while the latter two are functions.

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⚫ Input/Output Functions
2. Integer I/O
a. putw( )
This function writes an integer value to the file pointed to by
file_pointer.
b. getw( )
This function returns the integer value from the file associated with
file_pointer.
3. String I/O
a. fputs( ) Note: String is value written in a file represented by ptr_variable
This function writes the null terminated string pointed by given
character pointer to a file.
Syntax: fputs( string, file_ptr_variable);
Note: int_value is no of character of string read from a file
b. fgets()
represented by ptr_variable and stored in string_variable
This function is used to read characters from a file and these
characters are stored in the string pointed by a character pointer.
Syntax: fgets( string_variable ,int_value, file_ptr_variable);
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 ⚫ Input/Output Functions
4. Formatted I/O
a. fprintf( )
This function is same as the printf( ) function but it writes formatted
data into the file instead of the standard output(screen). This function
has same parameters as in printf( ) but it has one additional
parameter which is a pointer of FILE type, that points to the file to
which the output is to be written.
Syntax: fprintf(file_ptr_variable, “control_string”, list_varaibales);
b. fscanf( )
This function is similar to the scanf( ) function but it reads data from
file instead of standard input, so it has one more parameter which is
a pointer of FILE type and it points to the file from which data will be
read.
Syntax: fscanf(file_ptr_variable, “control_string”, &list_varaibales);

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 ⚫ Input/Output Functions
5. Block Read/Write
a. fwrite( )
This function is used for writing an entire block to a given file.
Syntax: fwrite(&ptr, size_of_array_or_structure,
number_of_array_or_structure, fptr);

b. fread( )
This function is used to read an entire block from a given file.
Syntax: fread(&ptr, size_of_array_or_structure,
number_of_array_or_structure, fptr);

Ptr is the address of array or structure to be written or read.

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 ⚫ Random file processing/accessing
In this technique the content are stored sequentially and read back
the content from any position of the file. And it can be performed
using some function like rewind( ), fseek( ) and ftell( ).
1. rewind( )
The rewind( ) function places the file pointer to the beginning of the
file.
rewind(file_pointer);
2. fseek( )
This function is used for setting the file position pointer at the
specified byte.
fseek(file_pointer, offset, mode);
3. ftell( )
This function returns the current position of the file position pointer.
The value is counted from beginning of the file.
position=ftell(fp); where position is long int.
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 ⚫ Random file processing/accessing
fseek(file_pointer, offset, mode);

a. fseek(ptr, 0, SEEK_SET); moves file pointer to the beginning of

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 . . . to be continued !!!

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