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16 Cards in this Set
- Front
- Back
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What are the 3 parts of run-time memory ? |
Code area ( main program, subprograms ) , Data area ( run time stack, the heap ) , Control Information ( current IP indicates the instruction about to be executed , current EP shows the activation record of the current block, giving access to local and non-local data ) |
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How every subprogram is represented ? |
Represented as an activation record (AR) on the activation stack. The AR of the callee is placed at the top of the stack, directly above the AR of the caller |
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What are some important characteristics about the caller ? |
It has a pointer to the caller's activation record, a return address, and if this is a function, the addess where its value should be stored |
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What are some important characteristics about the callee ? |
It has scoping information ( a pointer to the AR of the enclosing block ), local variables, formal parameters, and temporary storage |
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What are the elements of an Activation Record ? |
A dynamic link DL ( pointer to caller's AR ), a static link SL ( pointer to enclosing block ), a return address, and local data |
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What is the subprogram call sequence ? |
First, the compiler generates prologue for entering the subprogram, then the compiler generates code to execute the subprogram body, finally the compiler generates epilogue for exiting the subprogram |
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What is the prologue ? |
The prologue is made of a segment of free stack storage ( stack frame ). Then it puts in the new stack frame all data about the caller and the callee. |
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What is the epilogue ? |
It stores the returned value ( if subprogram is a function ) , move the top-of-stack pointer down ( same as removing the AR from the stack ), it jumps to the return address, and continues executing statements in the caller's body |
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What are the 6 attributes that characterize a variable ? |
Name, Address ( storage ), Value, Type, Lifetime, Scope |
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What is a binding ? |
It is an association between two entities |
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What is the binding time ? |
Time at which a binding takes place |
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When do a a binding is static ? |
If it occurs before runtime and remains unchanged during the program execution |
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When do a binding is dynamic ? |
If it first occurs at runtime and/or can change during program execution |
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For the name, value, address, type, and score of a variable, when are the attributes defined ? |
Name : generally at compile-time, the value at run-time, the address at load-time and run-time, and the type and the scope at compile-time and run-time |
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What is the lifetime of a global/static variable ? |
It is the load-time through end of program execution |
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What is the lifetime of a local/parameter variable ? |
Subprogram execution |
