FILE Open Read Write Seek

A compact demonstration of the C runtime file functions on Windows: fopen in binary mode ("rb"/"wb"), reading and writing one character at a time with fscanf/fprintf, rewinding with fseek, and then copying the same file much faster using fread/fwrite in 512-byte blocks. It is a good reference for when you want to see the classic open-copy-seek-close pattern without any Win32 CreateFile ceremony - the buffered loop's while(BufferSize == MaxBuffer) idiom is the standard way to detect the final partial block.

#include <windows.h>
#include <stdio.h>

#define MaxBuffer 512

int main()
{
    FILE *LocalSource;
    FILE *LocalTarget;

    char *SourceName = "C:/Windows/Desktop/Source.Txt";
    char *TargetName = "C:/Windows/Desktop/Target.Txt";

    char Buffer[MaxBuffer+1];

    char CharBuffer = '\0';

    int End_Of_File = 0;
    int BufferSize = 0;

    /* Open File For Binary Read */
    if((LocalSource = fopen(SourceName,"rb")) == NULL)
    {
        printf("Could Not Open %s For Read.",SourceName);
        return 0;
    }

    /* Open File For Binary Write */
    if((LocalTarget = fopen(TargetName,"wb")) == NULL)
    {
        printf("Could Not Open %s For Write.",TargetName);
        return 0;
    }

    /* Write Source File To Target File One Character At A Time */
    while (End_Of_File != EOF)
    {
        End_Of_File = fscanf(LocalSource, "%c", &CharBuffer);
        if (End_Of_File != EOF)
        {
            fprintf(LocalTarget, "%c", CharBuffer);
        }
    }

    // SEEK_SET 0   File beginning
    // SEEK_CUR 1   Current file pointer position
    // SEEK_END 2   End-of-file

    /* Seek To Beginning Of File */
    fseek(LocalSource, 0L, SEEK_SET);

    /* Write Source File To Target File One Buffer At A Time */
    do
    {
        BufferSize = fread(Buffer, sizeof(char), MaxBuffer, LocalSource);
        fwrite(Buffer, sizeof(char), BufferSize, LocalTarget);
    }
    while(BufferSize == MaxBuffer);

    if(LocalSource) fclose(LocalSource);
    if(LocalTarget) fclose(LocalTarget);

    return 0;
}

The comment block before the fseek call doubles as a quick reference for the three seek origins: SEEK_SET (beginning), SEEK_CUR (current position), and SEEK_END (end of file).