Overflow Flag - Revision history

Mr z: Protected "Overflow Flag" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2010-12-04T09:01:12Z

Protected "Overflow Flag" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

Mr z at 00:42, 12 January 2005

2005-01-12T00:42:46Z

Mr z: /* a little more info to make it clearer */

2005-01-12T00:40:45Z

‎a little more info to make it clearer

Mr z: /* Overflow's complicated! */

2005-01-12T00:36:13Z

‎Overflow's complicated!

Pingaso at 00:14, 12 January 2005

2005-01-12T00:14:39Z

New page

The Overflow Flag indicates that the previous operation resulted in a signed number that was too large or too small to be contained in a single register.

← Older revision		Revision as of 00:42, 12 January 2005
Line 1:		Line 1:
−	The Overflow Flag indicates that the previous operation resulted in a signed number whose sign was inconsistent with the signs of the operands that produced it. For instance, the Overflow Flag gets set when adding two positive numbers produces a negative result, or adding two negative numbers produces a positive result.	+	The Overflow Flag indicates that the previous operation resulted in a signed number whose sign was inconsistent with the signs of the operands that produced it—signed integer overflow. For instance, the Overflow Flag gets set when adding two positive numbers produces a negative result, or adding two negative numbers produces a positive result.

	The truth table below indicates when the CPU sets or clears the Overflow Flag:		The truth table below indicates when the CPU sets or clears the Overflow Flag:

@@ Line 4: / Line 4: @@
 <center>
 <table border=1>
-<tr><th COLSPAN=4>Addition</TH></tr>
+<tr><th COLSPAN=5>Addition</TH></tr>
-<tr><th>Sign of first operand</th><th>Sign of second operand</th><th>Sign of result</th><th>Resulting value of Overflow Flag</th></tr>
+<tr><th>Sign of first operand</th><th>Sign of second operand</th><th>Sign of result</th><th>Resulting value of Overflow Flag</th><th>Notes</th></tr>
 <tr><td>0</td><td>0</td><td>0</td><td>0</td></tr>
-<tr><td>0</td><td>0</td><td>1</td><td>1</td></tr>
+<tr><td>0</td><td>0</td><td>1</td><td>1</td><td>Adding two positive numbers produced a negative result</td></tr>
 <tr><td>0</td><td>1</td><td>0</td><td>0</td></tr>
 <tr><td>0</td><td>1</td><td>1</td><td>0</td></tr>
 <tr><td>1</td><td>0</td><td>0</td><td>0</td></tr>
 <tr><td>1</td><td>0</td><td>1</td><td>0</td></tr>
-<tr><td>1</td><td>1</td><td>0</td><td>1</td></tr>
+<tr><td>1</td><td>1</td><td>0</td><td>1</td><td>Adding two negative numbers produced a positive result</td></tr>
 <tr><td>1</td><td>1</td><td>1</td><td>0</td></tr>
-<tr><th COLSPAN=4>Subtraction</TH></tr>
+<tr><th COLSPAN=5>Subtraction</TH></tr>
-<tr><th>Sign of value being subtracted (subtrahend)</th><th>Sign of value being subtracted from (minuend)</th><th>Sign of result</th><th>Resulting value of Overflow Flag</th></tr>
+<tr><th>Sign of value<br/>being subtracted<br/>(subtrahend)</th><th>Sign of value<br/>being subtracted from<br/>(minuend)</th><th>Sign of result</th><th>Resulting value of Overflow Flag</th></tr>
 <tr><td>0</td><td>0</td><td>0</td><td>0</td></tr>
 <tr><td>0</td><td>0</td><td>1</td><td>0</td></tr>
-<tr><td>0</td><td>1</td><td>0</td><td>1</td></tr>
+<tr><td>0</td><td>1</td><td>0</td><td>1</td><td>Subtracting a positive number from a negative number gave a positive result.</td></tr>
 <tr><td>0</td><td>1</td><td>1</td><td>0</td></tr>
 <tr><td>1</td><td>0</td><td>0</td><td>0</td></tr>
-<tr><td>1</td><td>0</td><td>1</td><td>1</td></tr>
+<tr><td>1</td><td>0</td><td>1</td><td>1</td><td>Subtracting a negative number from a positive number gave a negative result.</td></tr>
 <tr><td>1</td><td>1</td><td>0</td><td>0</td></tr>
 <tr><td>1</td><td>1</td><td>1</td><td>0</td></tr>
 </table></center>

← Older revision		Revision as of 00:36, 12 January 2005
Line 1:		Line 1:
−	The Overflow Flag indicates that the previous operation resulted in a signed number that ~~was too large~~ or ~~too small to be contained in~~ a ~~single register~~.	+	The Overflow Flag indicates that the previous operation resulted in a signed number whose sign was inconsistent with the signs of the operands that produced it. For instance, the Overflow Flag gets set when adding two positive numbers produces a negative result, or adding two negative numbers produces a positive result.
		+
		+	The truth table below indicates when the CPU sets or clears the Overflow Flag:
		+	<center>
		+	<table border=1>
		+	<tr><th COLSPAN=4>Addition</TH></tr>
		+	<tr><th>Sign of first operand</th><th>Sign of second operand</th><th>Sign of result</th><th>Resulting value of Overflow Flag</th></tr>
		+	<tr><td>0</td><td>0</td><td>0</td><td>0</td></tr>
		+	<tr><td>0</td><td>0</td><td>1</td><td>1</td></tr>
		+	<tr><td>0</td><td>1</td><td>0</td><td>0</td></tr>
		+	<tr><td>0</td><td>1</td><td>1</td><td>0</td></tr>
		+	<tr><td>1</td><td>0</td><td>0</td><td>0</td></tr>
		+	<tr><td>1</td><td>0</td><td>1</td><td>0</td></tr>
		+	<tr><td>1</td><td>1</td><td>0</td><td>1</td></tr>
		+	<tr><td>1</td><td>1</td><td>1</td><td>0</td></tr>
		+	<tr><th COLSPAN=4>Subtraction</TH></tr>
		+	<tr><th>Sign of value being subtracted (subtrahend)</th><th>Sign of value being subtracted from (minuend)</th><th>Sign of result</th><th>Resulting value of Overflow Flag</th></tr>
		+	<tr><td>0</td><td>0</td><td>0</td><td>0</td></tr>
		+	<tr><td>0</td><td>0</td><td>1</td><td>0</td></tr>
		+	<tr><td>0</td><td>1</td><td>0</td><td>1</td></tr>
		+	<tr><td>0</td><td>1</td><td>1</td><td>0</td></tr>
		+	<tr><td>1</td><td>0</td><td>0</td><td>0</td></tr>
		+	<tr><td>1</td><td>0</td><td>1</td><td>1</td></tr>
		+	<tr><td>1</td><td>1</td><td>0</td><td>0</td></tr>
		+	<tr><td>1</td><td>1</td><td>1</td><td>0</td></tr>
		+	</table></center>

← Older revision	Revision as of 09:01, 4 December 2010
(No difference)