March 19, 2003
Slashdot: US May Nerf Non-Military GPS During War

Following a Space Daily story, Slashdot is reporting that the U.S. government may be degrading GPS satellite signals to hamper Iraqi forces' ability to use those systems during the war. This could potentially reduce accuracy from 3 meters to over 100 meters. The U.S. will do this by increasing the inaccuracies on the civilian C/A code, turning back on S/A (Selective Availability), by having the satellites deliberately and randomly return inaccurate information on where they are. S/A degrades GPS accuracy to only 100 meters 95 percent of the time and 300 meters the other 5 percent of the time.

People depending on GPS systems may want to do sanity checks on any data returned by those systems during the war.

Posted by Darren Wershler-Henry at March 19, 2003 11:32 AM
Comments

Note the new asterisks whenever we reference favoriteNumber, except for that new line right before the return.

Posted by: Joyce on January 19, 2004 03:41 AM

To address this issue, we turn to the second place to put variables, which is called the Heap. If you think of the Stack as a high-rise apartment building somewhere, variables as tenets and each level building atop the one before it, then the Heap is the suburban sprawl, every citizen finding a space for herself, each lot a different size and locations that can't be readily predictable. For all the simplicity offered by the Stack, the Heap seems positively chaotic, but the reality is that each just obeys its own rules.

Posted by: Susanna on January 19, 2004 03:42 AM

The Stack is just what it sounds like: a tower of things that starts at the bottom and builds upward as it goes. In our case, the things in the stack are called "Stack Frames" or just "frames". We start with one stack frame at the very bottom, and we build up from there.

Posted by: Isaac on January 19, 2004 03:43 AM

This code should compile and run just fine, and you should see no changes in how the program works. So why did we do all of that?

Posted by: Gerrard on January 19, 2004 03:44 AM

When a variable is finished with it's work, it does not go into retirement, and it is never mentioned again. Variables simply cease to exist, and the thirty-two bits of data that they held is released, so that some other variable may later use them.

Posted by: Christopher on January 19, 2004 03:44 AM
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