Four bit adder: Difference between revisions

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@@ Line 984: / Line 984: @@
 =={{header|PL/I}}==
 <lang PL/I>
+/* 4-BIT ADDER */       /* 14 August 2010 */
-/* A 4-bit adder. */
 TEST: PROCEDURE OPTIONS (MAIN);
-   DECLARE CARRY BIT (1) ALIGNED;
    DECLARE CARRY_IN BIT (1) STATIC INITIAL ('0'B) ALIGNED;
    declare (m, n, sum)(4) bit(1) aligned;
@@ Line 992: / Line 992: @@
    get edit (m, n) (b(1));
-   put edit (m, ' + ', n, ' = ') (4 b, a, 4 b, a);
+   put edit (m, ' + ', n, ' = ') (4 b, a);
    do i = 4 to 1 by -1;
-      call full_adder (carry_in, m(i), n(i), sum(i), carry);
+      call full_adder ((carry_in), m(i), n(i), sum(i), carry_in);
-      carry_in = carry;
    end;
    put edit (sum) (b);
@@ Line 1,003: / Line 1,002: @@
    DECLARE (IN1, IN2, SUM, CARRY) BIT (1) ALIGNED;
-   SUM = ^( (IN1 & IN2) | ( ^IN1 & ^IN2) );
+   SUM = ( ^IN1 & IN2) | ( IN1 & ^IN2);
+         /* Exclusive OR using only AND, NOT, OR. */
    CARRY = IN1 & IN2;