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CSCI261
Lecture 27: Events, Interrupts & Event Handling Memory, Stack, Stack Frames, The Heap
Attribution: http://123rf.com
CSCI261 Lecture 27: Events, Interrupts & Event Handling Memory, - - PowerPoint PPT Presentation
CSCI261 Lecture 27: Events, Interrupts & Event Handling Memory, - - PowerPoint PPT Presentation
CSCI261 Lecture 27: Events, Interrupts & Event Handling Memory, Stack, Stack Frames, The Heap Attribution: http://123rf.com keypress Keyboard Interface (Serial USB) Bus CPU Operating System Application keypress Keyboard Interface
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Keyboard Interface (Serial USB) Bus CPU Operating System Application
keypress
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Keyboard Interface (Serial USB) Bus CPU Operating System Application
keypress electrical signal hardware “interrupt”
“oooh, a keypress event” event handler
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Event Loop
Modern graphical programs wait in an infinite “event loop,” waiting for some events to happen. update(); draw(); update(); draw(); update(); draw();
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Event Handling
When an event occurs, call a function. an “event handler”
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OF Event Handlers
- keyPressed
- keyReleased
- mouseMoved
- mouseDragged
- mousePressed
- mouseReleased
- windowResized
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Memory & Functions
- Stack
- Stack Frames
- The Heap
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The Stack
LIFO
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int main() { int x = 2; int y = 5; int z = sum(x, y); }
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?
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int main() { int x = 2; int y = 5; int z = sum(x, y); }
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int sum(int x, int y) { return x + y; }
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local variables
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int main() { int x = 2; int y = 5; int z = sum(x, y); }
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int sum(int x, int y) { return x + y; }
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stack frame
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int main() { int x = 2; int y = 5; int z = sum(x, y); }
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int sum(int x, int y) { return x + y; }
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Stack Frames
One aspect of where “scope” comes from. Contains parameter values, local variable values, and “bookkeeping” information. Function call? New stack frame. Function return? Pop the entire stack frame.
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Problem
Things created within functions “go away” after the function returns... ... and sometimes, we want those “things” to stick around after the function returns.
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Problem
Storing too much on the stack can cause “stack overflow” http://stackoverflow.com
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Problem
In many cases, we do not know how much memory to allocate at compile time. We must allocate memory dynamically, during run-time.
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Is there another place we can store stuff?
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The Heap
A pool of unused memory, for your programs to use.
aka “the free store”
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Stack vs. Heap
- rganized
efficient accessed “directly” storage of “things” known in advance and more... unorganized less efficient (but we don’t care) dynamic storage and more...
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Heap
The exact location of things on the heap is not known in advance. How can your code access data whose locations are not known in advance?
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How can your code access data whose locations are not known in advance?
Pointers
(to be continued)
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Homework
Choose final project partners and send your instructor an email.