C Programming Week 4
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Questions and Answers

What is primarily tracked by the stack pointer in memory management?

  • The last used memory address
  • The number of function calls
  • The next free location on the stack (correct)
  • The total memory allocated

What happens when data overruns its allocated chunk in C?

  • The program will terminate immediately
  • Adjacent data may become corrupted (correct)
  • Memory is freed automatically
  • An automatic error message is displayed

Which of the following is a consequence of fragmentation in heap memory?

  • Heap memory becomes automatically cleared
  • Memory leaks are eliminated
  • Adjacent free memory may not be available despite total free space being adequate (correct)
  • Memory allocation requests always succeed

Which of the following best describes stack memory?

<p>Memory may be reused by subsequent function calls (B)</p> Signup and view all the answers

What role does the compiler play in stack management?

<p>It generates code for pushing and popping data onto/from the stack (A)</p> Signup and view all the answers

Which of the following is a potential problem when using heap memory?

<p>Difficulty in keeping track of allocated memory leading to leaks (A)</p> Signup and view all the answers

What happens to the memory allocated on the stack after a function call has completed?

<p>It is available for reuse by the next function call (A)</p> Signup and view all the answers

What is a major risk associated with heap memory allocation?

<p>Memory leaks if not properly freed (D)</p> Signup and view all the answers

What does the Last-In, First-Out (LIFO) principle indicate about the function-call stack?

<p>The last item added is the first one to be removed. (B)</p> Signup and view all the answers

What is stored in a stack frame when a function is called?

<p>Return address and local variables. (A)</p> Signup and view all the answers

What happens when the maximum stack size is exceeded during function calls?

<p>A stack overflow error occurs. (B)</p> Signup and view all the answers

How does control return to the calling function after a function execution is complete?

<p>By using the return address stored in the stack frame. (C)</p> Signup and view all the answers

Why is it necessary to know argument values before calling a function like printf?

<p>To correctly push the function's stack frame onto the stack. (D)</p> Signup and view all the answers

Which statement about stack frames is correct?

<p>Each stack frame is popped off when the function completes. (B)</p> Signup and view all the answers

In the context of memory organization, what characterizes the stack compared to the heap?

<p>Memory allocation on the stack is generally faster. (C)</p> Signup and view all the answers

When does the main function terminate during a program execution?

<p>After all function calls have completed and their frames are popped off. (A)</p> Signup and view all the answers

What is a key feature of the heap compared to the stack?

<p>Heap memory allows for the allocation of different sizes of memory blocks during execution. (C)</p> Signup and view all the answers

What happens when memory is allocated on the heap and the requested size does not match an existing free chunk?

<p>A portion of an existing free chunk is split off, creating a new chunk. (D)</p> Signup and view all the answers

Which statement about freeing memory in the heap is accurate?

<p>Freeing memory allows adjacent free chunks to be merged into a larger free chunk. (C)</p> Signup and view all the answers

What is a major drawback of using heap memory for allocation?

<p>It requires more CPU overhead, making it slower to access than stack memory. (C)</p> Signup and view all the answers

Which of the following statements is true about memory fragmentation in the heap?

<p>Frequent allocation and deallocation leads to small, scattered free blocks, making larger allocations difficult. (C)</p> Signup and view all the answers

Which memory structure is primarily used for storing global variables and dynamically allocated data during runtime?

<p>Heap (B)</p> Signup and view all the answers

What must be explicitly done when memory allocated on the heap is no longer needed?

<p>The programmer must manually free the memory. (D)</p> Signup and view all the answers

How does stack memory compare to heap memory in terms of data storage?

<p>Stack memory is faster but has less flexibility in terms of size. (D)</p> Signup and view all the answers

What mechanism allows for the addition and removal of stack frames in the function-call stack?

<p>Last-In, First-Out (LIFO) (B)</p> Signup and view all the answers

What occurs when a function completes its execution in relation to the stack?

<p>The function's stack frame is popped off the stack. (B)</p> Signup and view all the answers

What is a potential consequence of exceeding the maximum stack size during function calls?

<p>Stack overflow error (A)</p> Signup and view all the answers

In the context of a function calling process, what must happen before calling a function like printf?

<p>All argument values for the function must be known. (A)</p> Signup and view all the answers

What structure is used to maintain the return address and local variables for function calls?

<p>Call stack (B)</p> Signup and view all the answers

What is a key benefit of using heap memory over stack memory?

<p>It allows allocation of varying sizes of memory blocks during execution. (D)</p> Signup and view all the answers

When a chunk of memory is freed in the heap, what occurs if it is adjacent to another free chunk?

<p>The chunks are merged into a larger free chunk. (C)</p> Signup and view all the answers

What is a consequence of frequent memory allocation and freeing on the heap?

<p>Fragmentation leading to difficulty in allocating larger blocks. (C)</p> Signup and view all the answers

What must be done explicitly to keep memory allocated on the heap from persisting indefinitely?

<p>It must be manually freed when no longer needed. (B)</p> Signup and view all the answers

What happens when a request for memory on the heap exactly matches an existing free chunk?

<p>The existing chunk is returned and marked as allocated. (A)</p> Signup and view all the answers

Flashcards

Heap Pitfalls

Memory management issues can arise when allocating and freeing memory on the heap.

Memory Leaks (Heap)

Failing to free allocated memory leads to wasted resources.

Heap Fragmentation

Free memory chunks scattered across the heap make it hard to allocate contiguous memory.

Stack

Dynamic memory for local variables, function parameters, and return addresses.

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Stack Pointer

CPU register tracking available memory on the stack.

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Stack Ephemerality

Memory on the stack is temporary; reused for new function calls.

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Stack Usage

Local variables, function arguments, current execution context are temporarily stored in the stack.

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Data Overruns (Heap)

Writing beyond allocated memory boundaries corrupts data in adjacent memory regions.

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Heap Memory

A large memory area used for dynamic memory allocation during program execution.

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Heap Allocation

The process of requesting and receiving a block of memory from the heap.

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Heap Memory Persistence

Allocated memory remains in the heap until explicitly deallocated.

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Heap Memory Allocation (Matching)

If you need memory, the system looks for a matching free block; if found, it's used.

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Heap Memory Allocation (Splitting)

If no exact match is found, a larger block is split into a needed smaller block, and a remainder part.

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Heap Memory Freeing (Merging)

When freeing memory, adjacent free blocks can be combined, creating a larger continuous block.

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Stack Memory

A different memory area used to store local variables and function calls in a LIFO fashion.

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Stack Overflow

An error that occurs when the stack runs out of space due to too many nested function calls.

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Function Call Stack

Mechanism for managing function calls, returns, and tracking execution control flow.

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Return Address

The memory address where the program should return after a function call finishes.

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Local Variables

Variables defined within a particular function.

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LIFO (Last-In, First-Out)

A fundamental principle of the stack data structure where the last item added is the first one removed.

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Stack frame contains

A stack frame includes return address and local variables crucial for function-call management.

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Stack Data Structure

A memory area where data is added and removed in a "Last-In, First-Out" (LIFO) manner, like a stack of dishes.

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Stack Overflow Error

An error that occurs when the stack runs out of space, typically due to too many nested function calls.

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What data is stored in the heap?

The heap stores global variables, memory explicitly or implicitly allocated by the programmer, and some literals. This memory remains persistent until explicitly freed.

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Heap - Memory Fragmentation

Over time, the heap might become fragmented with small, scattered free memory blocks. This can make it difficult to allocate large contiguous blocks.

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Heap - How is memory freed?

When you free allocated memory, the corresponding chunk in the heap table is marked as free. If the freed memory is adjacent to another free chunk, they are merged.

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Heap - How is memory allocated?

The system searches for the best-fitting free chunk in the heap. Either the exact size is found and used, or a larger chunk is split to accommodate the requested size.

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Study Notes

C Programming - Stack vs Heap

  • The stack and heap are memory locations used to store data in C programs
  • The stack is a continuously changing block of memory used to store local variables, function arguments
  • Variables declared within a function or statement block are stored on the stack
  • The stack pointer tracks the next free location in the stack
  • The stack pointer decrements when data is pushed onto the stack
  • The compiler handles pushing onto and pulling data from the stack
  • Stack values are not permanent; they are overwritten by subsequent function calls
  • Data overruns can occur when data is written beyond the end of an array
  • Risks a stack overflow if too many functions call each other
  • A stack overflow can corrupt information or cause the stack and heap to collide
  • A stack overflow can happen with endless recursion

Heap Memory

  • A block of memory used to store global variables, variables that are explicitly/implicitly allocated at runtime, and some literals
  • Programs can allocate memory on the heap at runtime
  • Memory allocated is persistent until explicitly freed by the program.
  • Data whose size may change during execution is suitable for the heap
  • Heap memory access can be slower than stack memory, requiring more overhead to find free blocks
  • Repeated allocating and freeing memory over time can lead to fragmentation, where free memory may not be contiguous and is often in smaller blocks
  • When allocating memory on the heap, the address of the best-matching chunk is returned to the program
  • If no matching chunk is found, part of an existing free block can be split to allocate the requested memory size

Stack Frame

  • A stack frame is created whenever a function is called, and it is pushed onto the stack
  • A stack frame consists of the return address and local variables for the function
  • When a function completes, its stack frame is popped off the stack
  • Control then transfers to the return address in the stack frame

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Stack vs Heap in C Programming (PDF)

Description

This quiz explores the differences between stack and heap memory in C programming. Learn about how data is stored, the role of the stack pointer, and the potential risks like stack overflow. Test your understanding of memory management concepts in C languages.

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