5 DIM A(10,11),V(10)
10 PRINT "ENTER N":INPUT N
15 PRINT "ENTER MATRIX" 
20 FOR S=1 TO N 
25 INPUT A(S,1),A(S,2),A(S,3),A(S,4),A(S,5),A(S,6),A(S,7),A(S,8),           A(S,9),A(S,10),A(S,11)
30 NEXT S 
35 FOR S=1 TO N 
40 FOR T=S TO N:IF A(T,S)<>0 THEN 50:NEXT T 
45 PRINT "MATRIX SINGULAR":GOTO 999  
50 GOSUB 500 
55 A(S,S)=1/A(S,S):GOSUB 600 
60 FOR T=1 TO N:IF T=S THEN 70 
65 B=-A(T,S): A(T,S)=0:GOSUB 700
70 NEXT T:NEXT S 
100 FOR S=N TO 1 STEP -1:IF V(S)=S THEN 140 
110 FOR J=1 TO N  
120 B=A(J,S): A(J,S)=A(J,V(S)): A(J,V(S))=B
130 NEXT J  
140 NEXT S:GOTO 800  
500 FOR J=1 TO N  
510 B=A(S,J): A(S,J)=A(T,J): A(T,J)=B
520 NEXT J: V(S)=T:RETURN 
600 FOR J=1 TO N:IF J=S THEN 620 
610 A(S,J)=A(S,S)*A(S,J)  
620 NEXT J:RETURN 
700 FOR J=1 TO N  
710 A(T,J)=A(T,J)+B*A(S,J) 
720 NEXT J:RETURN 
800 FOR I=1 TO N:PRINT :FOR J=1 TO N:PRINT A(I,J), 
810 NEXT J:PRINT :NEXT I 
999 END 

