--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/abcddim.m	Fri Aug 13 21:03:40 1993 +0000
@@ -0,0 +1,55 @@
+function [n, m, p] = abcdchk (a, b, c, d)
+
+# Usage: [n, m, p] = abcdchk (a, b, c, d)
+#
+# Check for compatibility of the dimensions of the matrices defining
+# the linear system (a, b, c, d).
+#
+# returns n = number of system states, 
+#         m = number of system inputs
+#         p = number of system outputs
+#
+# returns n = m = p = -1 if system is not compatible
+
+  if (nargin != 4)
+    error ("abcdchk: illegal number of arguments.  Need four.")
+  endif
+
+  n = -1;
+  m = -1;
+  p = -1;
+
+  [an, am] = size (a);
+  if (an != am)
+    disp ("abcdchk: a is not square");
+    return;
+  endif
+
+  [bn, bm] = size (b);
+  if (bn != am)
+    disp ("abcdchk: a, b are not compatible");
+    return;
+  endif
+
+  [cn, cm] = size (c);
+  if (cm != an)
+    disp ("abcdchk: a, c are not compatible");
+    return;
+  endif
+
+  [dn, dm] = size (d);
+  if (cn != dn)
+    disp ("abcdchk: c, d are not compatible");
+    return;
+  endif
+
+  if (bm != dm)
+    disp ("abcdchk: b, d are not compatible");
+    return;
+  endif
+
+  n = an;
+  m = bm;
+  p = cn;
+
+endfunction