Data commit

Task/Four-bit-adder/FreeBASIC/four-bit-adder.basic

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+sub half_add( byval a as ubyte, byval b as ubyte,_
+              byref s as ubyte, byref c as ubyte)
+    s = a xor b
+    c = a and b
+end sub
+
+sub full_add( byval a as ubyte, byval b as ubyte, byval c as ubyte,_
+              byref s as ubyte, byref g as ubyte )
+    dim as ubyte x, y, z
+    half_add( a, c, x, y )
+    half_add( x, b, s, z )
+    g = y or z
+end sub
+
+sub fourbit_add( byval a3 as ubyte, byval a2 as ubyte, byval a1 as ubyte, byval a0 as ubyte,_
+                 byval b3 as ubyte, byval b2 as ubyte, byval b1 as ubyte, byval b0 as ubyte,_
+                 byref s3 as ubyte, byref s2 as ubyte, byref s1 as ubyte, byref s0 as ubyte,_
+                 byref carry as ubyte )
+    dim as ubyte c2, c1, c0
+    full_add(a0, b0,  0, s0, c0)
+    full_add(a1, b1, c0, s1, c1)
+    full_add(a2, b2, c1, s2, c2)
+    full_add(a3, b3, c2, s3, carry )
+end sub
+
+dim as ubyte s3, s2, s1, s0, carry
+
+print "1100 + 0011 = ";
+fourbit_add( 1, 1, 0, 0,  0, 0, 1, 1,  s3, s2, s1, s0, carry )
+print carry;s3;s2;s1;s0
+
+print "1111 + 0001 = ";
+fourbit_add( 1, 1, 1, 1,  0, 0, 0, 1,  s3, s2, s1, s0, carry )
+print carry;s3;s2;s1;s0
+
+print "1111 + 1111 = ";
+fourbit_add( 1, 1, 1, 1,  1, 1, 1, 1,  s3, s2, s1, s0, carry )
+print carry;s3;s2;s1;s0