fread() Can Read More Than 64K at a Time

MS-DOS                 | WINDOWS

The information in this article applies to:

• The C Run-time (CRT), included with:

      - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, and 6.0ax
      - Microsoft C/C++ for MS-DOS, versions 7.0
      - Microsoft Visual C++ for Windows, versions 1.0, 1.51, and 1.52
  

SUMMARY

In Microsoft C it is possible to read more than 64K at a time with the fread() function by specifying an item size greater than 1 and a count from 1 to 64K. The resulting number of bytes read will be the product of size and count.

MORE INFORMATION

The follow code demonstrates how to read a file 200K in length:

Sample Code

/* Compile options needed: /AL
*/

#include <stdio.h>

char huge buffer[205000];

void main(void)

     FILE *fp;

     fp=fopen("testfile.dat","r");

     fread(buffer,4,51200,fp);     /* 51200*4=204,800 */

    /* The value returned from the line above will be the number of
       items read. This number is limited to 64K because it is of
       type size_t. But remember, the total number of bytes read is
       equal to the number of items times the size of each item, which
       is 4 bytes in this case. Therefore, the total bytes read
       is 4 times 51200 or 204,800 bytes. */