Ed source code

while :;do read x;echo \?;done

plain text version

Here is the source code in x86 assembly (submitted by Nate):

[ORG 0x100]
top: mov ah,0x0a
 mov dx, buffer
 int 0x21
 mov ah, 0x09
 mov dl,message
 int 0x21
 jmp short top
message:
 db 10,'?',13,10,'$'
buffer:

Another variant, submitted by Hunter Turcin:

#include <iostream>
#include <string>
using namespace std;
int
main()
{
 string huh;
 for (;;)
 {
 getline(cin, huh);
 cout << "?\n";
 }
 return 0;
}