Помогите разобрать код

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#define ENC(c) ((c) ? ((c) & 077) + ' ': '`')
static void uuencode (FILE *f,char *nom) 
{
    int ch, n,idx,count;
    register char *p;
    char buf[80],outbuf[250];
    FILE *in;
    in = fopen(nom,"rb");
    if (in == NULL) return;
    p = strrchr(nom,'\\');
    if (p) p++;
    else p = nom;
    fprintf(f,"\r\nbegin 0666 %s\r\n",p); 
    while ((n = fread (buf, 1, 45, in)) != 0)
    {
        idx = 0;
        ch = ENC (n);
        outbuf[idx++] = ch;
        for (p = buf; n > 0; n -= 3, p += 3)
        {
            ch = *p >> 2;
            ch = ENC (ch);
            outbuf[idx++] = ch;
            ch = ((*p << 4) & 060) | ((p[1] >> 4) & 017); 
            ch = ENC (ch);
            outbuf[idx++] = ch;
            ch = ((p[1] << 2) & 074) | ((p[2] >> 6) & 03); 
            ch = ENC (ch);
            outbuf[idx++] = ch;
            ch = p[2] & 077;
            ch = ENC (ch);
            outbuf[idx++] = ch;
        }
        outbuf[idx++] = '\r';
        outbuf[idx++] = '\n';
        outbuf[idx] = 0;
        count =  fwrite(outbuf, 1,idx,f);
        if (count != idx) break;
    }
    fprintf(f,"%c\r\nend\r\n",ENC(0));
    fclose(in);
}
int _tmain(int argc, _TCHAR* argv[])
{
    FILE *f;
    if (argc <= 2) {
        printf("Usage %s <input file> <encoded output file>\n",argv[0]); 
        return(1);
    }
    f = fopen((const char*)argv[2],"wb");
    if (f == NULL) {
        printf("Impossible to open %s\n",argv[2]); 
        return(1);
    }
    uuencode(f,(char*)argv[1]);
    fclose(f);
    printf("Result encoded in %s\n",argv[2]); 
    return(0);
}