getw, putw, fprintf and fscanf C Programming functions

THE getw AND putw FUNCTIONS

These are integer‒oriented functions. They are similar to getc and putc functions and are used to read and write integer values. These functions would be useful when we deal with only integer data.

Syntax:

putw(integer,fp);

getw(fp);

/*Example program for using getw and putw functions*/

#include <stdio.h>

#include <conio.h>

main()

{

FILE *fl, *f2, *f3;

int n, i;

clrscr();

printf("Contents of the data file\n\n");

fl=fopen("DATA", "w");

for(i=1;i < = 10;i++)

{

         scanf("%d", &n);

         if(n ==‒1)  break;

         putw (n,fl);

}

fclose(fl);

fl=fopen("DATA", "r");

f2=fopen("ODD", "w");

f3=fopen("EVEN", "w");

while((n=getw (f1))!= EOF) * Read from data file*!

{

         if(n%2==0) putw(n,f3); /*Write to even file*/

         else putw (n,f2);  /*write to odd File*/

}

fclose(fl);

fclose(f2);

fclose(f3);

f2=fopen("ODD", "r");

f3=fopen("EVEN", "r");

printf("\n\n Contents of the odd file\n\n");

while((n=getw (f2))!= EOF) printf("%d\t",n);

printf("\n\nContents of the even file\n");

while((n=getw (f3))!= EOF) printf("%d\t",n);

fclose(f2);

fclose(f3);

}

OUTPUT

Contents of the data file

1 2 3 4 5 6 7 8 9 10

Contents of the odd file

1 3 5 7 9

Contents of the even file

2 4 6 8 10

THE fprintf & fscanf FUNCTIONS

The fprintf and fscanf functions are similar to printf and scanf functions except that they work on files. The first argument of theses functions is a file pointer which specifies the file to be used.

Syntax :

fprintf(fp, "control string", list);

Description:

Fp is a file pointer associated with a file that has been opened for writing.

control string is file output specifications list may include variable, constant and string.

Example:

fprintf(fl,"%s %d", name, &age);

Where name is an array variable of type char and age is an int variable.

Syntax:

fscanf(fp, "control string", list);

Description:

fp is a file pointer associated with a file that has been opened for writing.

control string is file output specifications list may include variable, constant and string.

Example:

fscanf(f2,"%d %d", &item, & qty");

Where item is an int variable and qty is an int variable

This statement would cause the reading of data items from the file in the control string. Like scanf, fscanf also returns the number of items that are successfully read.

/*Program to handle mixed data types */

#include <stdio.h>

#include <conio.h>

main()

{

FILE *fp;

int num, qty, i;

float price, value;

char filename [10];

printf("Input filename....");

scanf("%s", filename);

fp=fopen(filename, "w");

printf("\nInput inventory data");

printf("Item number price quantity \n");

for(i=1;i<= 2;i++)

{

        fscanf(stdin, "%d %f%d", &num, & price, &qty);

        fprintf(fp, "%d %f%d", num, price, qty);

}

fclose (fp);

fp=fopen(filename, "r");

printf("\nItem number price quantity value\n");

fflush(stdin);

fflush(stdout);

for(i=1;i<= 2;i++)

{

        fscanf(fp, "%d %f%d", &num, & price, & qty);

        value=price*qty;

        fprintf(stdout, "%d\t%f\t%d\t%f\t\n", num, price, qty, value);

}

fclose(fp);

}

OUTPUT

Input filename...: vrb

Input inventory data Item number price quantity

1 10 10

2 20 20

Item number price quantity value

1                  10      10          100

2                  20      20          200