/in/foo.c: In function 'main':
/in/foo.c:4:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d%d",&m,&n);
  ^~~~~
/in/foo.c:4:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:4:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:7:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for (i=0;i<m;i++)
  ^~~
/in/foo.c:10:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   int k;
   ^~~
/in/foo.c:25:4: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    printf("%7d ",a[i][j]);
    ^~~~~~
/in/foo.c:25:4: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:25:4: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:26:3: warning: incompatible implicit declaration of built-in function 'printf'
   printf("%7d",a[i][j]);
   ^~~~~~
/in/foo.c:26:3: note: include '<stdio.h>' or provide a declaration of 'printf'