A factorial is a function in mathematics that multiplies a number by every number that precedes it.

int main(){
    int x = 7;
    printf("The factorial of the number is %d", fac(x));
    return 0;
}

int fac(int y)
{
    if (y == 0)
        return 1;
    return y * fac(y - 1);
}

Uxntal

@on-reset ( -> )
	#0007 fac
	#010e DEO
	BRK

@fac ( n* -: res* )
	ORAk ?{ POP2 #0001 JMP2r }
	DUP2 #0001 SUB2 fac MUL2
	JMP2r

Titan

using std.manip
using std.cond
using std.out

fac == [: [/ 1] [: 1 - fac ×] ⍉ 0 = ?]

7 fac .nl

Modal

<> (?0 ?1 `?:) (Int ?:)

<> (?n factorial) (Int ?n Int 1 fact)
<> (Int 0 Int ?a fact) (?a)
<> (Int ?n Int ?a fact) (?n 1 `- ?n ?a `* fact)

6 factorial