Here you can see a rough decompilation of DeHex from Fred's Fish Disks

#include <stdio.h>

main ()
{
	auto char buf[128];
	register int ch;
	register int packed;
	register char *scan;

	while (gets (buf)) {
		for (scan = buf; *scan != '\000'; ) {
			ch = *scan++;
			if (ch > '9') {
				packed = (ch - '7') << 4;
			} else {
				packed = (ch - '0') << 4;
			}
			ch = *scan++;
			if (ch > '9') {
				packed |= (ch - '7');
			} else {
				packed |= (ch - '0');
			}
			putchar (packed);
		}
	}
}

Private Sub usub_1500() {
if (sp != Global_468) {
        goto Label_16384;
}//EndIF; 240
do {
        usub_1536();
        if (usub_1536 == 0)
                goto Label_0;
        do {
                do {
                } while ((*  var_80(a6)) == 0);//LoopEndWh 260
                if ((*  var_80(a6)) > 57) {
                        BLocal1 = (((*  var_80(a6)) - 55) << 4);
                } else {
                        BLocal1 = (((*  var_80(a6)) - 48) << 4);
                }//EndIF; 28A
                if ((*  (var_80(a6) + 1)) > 57) {
                        BLocal1 = (BLocal1 | ((*  (var_80(a6) + 1)) - 55));
                } else {
                        BLocal1 = (BLocal1 | ((*  (var_80(a6) + 1)) - 48));
                }//EndIF; 2B0
                Global_7392 = (Global_7392 - 1);
                if ((Global_7392 - 1) == 0)
                        goto Label_1;
                Global_7384 = (Global_7384 + 1);
        }//LoopEnd 2D8
        Label_1:;
        usub_4928();
}//LoopEnd 2EC
Label_0:;
return(eax);
};