Source code in the xpl0 programming language

code ChOut=8, CrLf=9;
def  N=4;                       \number of objects (letters)
char S0, S1(N);

proc Permute(D);                \Display all permutations of letters in S0
int D;                          \depth of recursion
int I, J;
[if D=N then
        [for I:= 0 to N-1 do ChOut(0, S1(I));
        CrLf(0);
        return;
        ];
for I:= 0 to N-1 do
        [for J:= 0 to D-1 do    \check if object (letter) already used
                if S1(J) = S0(I) then J:=100;
        if J<100 then
                [S1(D):= S0(I); \object (letter) not used so append it
                Permute(D+1);   \recurse next level deeper
                ];
        ];
];

[S0:= "rose ";                  \N different objects (letters)
Permute(0);                     \(space char avoids MSb termination)
]