/in/foo.c: In function 'main':
/in/foo.c:5:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d",&m);
  ^~~~~
/in/foo.c:5:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:5:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:24:3: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
   printf("%5d ",a[i][j]) ;
   ^~~~~~
/in/foo.c:24:3: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:24:3: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:25:3: warning: incompatible implicit declaration of built-in function 'printf'
   printf("\n");
   ^~~~~~
/in/foo.c:25:3: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:7:12: warning: unused variable 't' [-Wunused-variable]
  int i,j,k,t=0; 
            ^
/in/foo.c:7:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k,t=0; 
          ^