Text Files

Files

• A collection of related data treated as a unit
• Files are store in secondary devices
• Read files - the data move from the external device to RAM
• Write files - the data move from RAM to external devices
• The data movement uses a special work area called buffer that act as a temporary storage area

Files and Streams

• A stream is a sequence of elements in time
• A file is define by using a standard FILE type
• The format for the file type is shown below
  • FILE *filename
• The asterisk is an address that pointed by the filename pointer

Standard Library Input/Output Functions

• The open/close functions, fopen and fclose, are used to open and close the association between external files and internal streams
• A file in C can be any of three basic modes:
  • reading, r
  • writing, w
  • appending, a
• Standard format
  • fopen ("filename", "mode");
• Example:

File *Infile;
Infile = fopen ("Data.dat", "w");

• When a file is opened in reading mode, the file marker is positioned at the beginning of the existing file
• When a file is opened in writing mode, the file marker is positioned at the beginning of the newly created empty file
• When a file is opened for appending, the file marker is positioned at the end of existing file, before the end-of-file marker
• fclose is used to closed and opened file
  • fclose(Infile);

Formatting Input/Output Functions

• Formatted input/output functions allow read data from and write data to file character by character while formatting to the desired data type
• scanf and fscanf are used for reading

File *fpInput;
fpInput = fopen("data.dat", "r");
fscanf(fpInput, "%d-%d-%d", &day, &month, &year);

• printf and fprintf are used for writing

File *fpOutput;
fpOutput = fopen("data.dat", "w");
fprintf(fpOutput, "The date is %d-%d-%d", day, month, year);

• Example

#include
void main () {
int num, sum = 0;
FILE *inptr, *outptr;


if ((inptr = fopen(“infile.txt”, “r”)) != NULL) {
     while(fscanf(inptr, “%d”, &num) != EOF)
        sum += num;
     fclose(inptr);
     if ((outptr = fopen(“outfile.txt”, “w”)) != NULL) {
        fprintf(outptr,“The sum of the numbers is %d\n”,sum);
     fclose(outptr);
     }
}
return ;

Character Input and Output

• Character input and output are used to read or write files character by character
• fgetc, getc, and getchar can be used for reading
• Example:
  • charatcter = getchar( ) //Get character from keyboard
  • character = getc(filepointer) //Get character from file
  • character = fgetc(file pointer) //Get character from file
• fputc, putc and putchar can be used for writing
• Example
  • putchar(character)
  • fputc (character, filepointer)
  • putc (character, filepointer