A file is a collection of bytes stored on a secondary storage device, which is generally a disk of some kind. The collection of bytes may be interpreted, for example, as characters, words, lines, paragraphs and pages from a textual document; fields and records belonging to a database; or pixels from a graphical image. There are two kinds of files that programmers deal with text files and binary files.
C Text Files
A text file can be a stream of characters that a computer can process sequentially. It is not only processed sequentially but only in forward direction. For this reason a text file is usually opened for only one kind of operation (reading, writing, or appending) at any given time.
C Binary Files
A binary file is no different to a text file. It is a collection of bytes. In C Programming Language a byte and a character are equivalent. No special processing of the data occurs and each byte of data is transferred to or from the disk unprocessed. C Programming Language places no constructs on the file, and it may be read from, or written to, in any manner chosen by the programmer.
Opening a File in C
The general format of the function used for opening a file is
The first statement declares the variable fp as a pointer to the data type FILE. As stated earlier, File is a structure that is defined in the I/O Library. The second statement opens the file named filename and assigns an identifier to the FILE type pointer fp. fopen() contain the file name and mode (the purpose of opening the file).
- r is used to open the file for read only.
- w is used to open the file for writing only.
- a is used to open the file for appending data to it.
Closing a File in C
A file must be closed as soon as all operations on it have been completed. This would close the file associated with the file pointer. The input output library supports the function to close a file.
myfile = fopen(“firstfile.txt”, “r”);
if (myfile == NULL)
printf(“File doesn’t exist\n”);
c = getc(myfile);
} while (c != EOF);
C File Operation Functions
|fopen()||Creates a new file. Opens an existing file.|
|fclose||Closes a file which has been opened for use|
|getc()||Reads a character from a file|
|putc()||Writes a character to a file|
|fprintf()||Writes a set of data values to a file|
|fscanf()||Reads a set of data values from a file|
|getw()||Reads a integer from a file|
|putw()||Writes an integer to the file|
|fseek()||Sets the position to a desired point in the file|
|ftell()||Gives the current position in the file|
|rewind()||Sets the position to the beginning of the file|