Activation records and call stack in Compiler Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the part of the call stack that stores information about a single function call.

Compiler Design

An activation record is also known as a [1].

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Aregister

Bheap block

Cstack frame

Dinstruction pointer

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing activation record with heap memory.

Thinking it is a CPU register.

An activation record is commonly called a stack frame. It holds data like local variables and return addresses for one function call.

2fill in blank

medium

Complete the code to describe what the call stack keeps track of during program execution.

Compiler Design

The call stack keeps track of [1] during program execution.

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Afunction calls and their activation records

Bhardware interrupts

Conly the main function

Dall global variables

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming it tracks global variables.

Confusing it with interrupt handling.

The call stack tracks function calls and their activation records to manage execution flow and local data.

3fill in blank

hard

Fix the error in the statement about the call stack's behavior.

Compiler Design

When a function finishes, its activation record is [1] from the call stack.

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Apushed

Bcopied

Cignored

Dpopped

Attempts:

3 left

💡 Hint

Common Mistakes

Saying the record is pushed instead of popped.

Thinking the record is copied or ignored.

When a function finishes, its activation record is popped off the call stack to free space and return control.

4fill in blank

hard

Fill both blanks to complete the description of what an activation record contains.

Compiler Design

An activation record contains [1] and [2] needed for function execution.

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Alocal variables

Breturn address

Cglobal constants

DCPU registers

Attempts:

3 left

💡 Hint

Common Mistakes

Including global constants which are not stored here.

Confusing CPU registers with activation record contents.

Activation records store local variables and the return address to resume execution after the function call.

5fill in blank

hard

Fill all three blanks to complete the explanation of the call stack's role in recursion.

Compiler Design

In recursion, each call creates a [1] on the call stack, storing [2] and [3].

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Astack frame

Bparameters

Creturn address

Dglobal variable

Attempts:

3 left

💡 Hint

Common Mistakes

Including global variables which are not stored per call.

Confusing parameters with global data.

Each recursive call creates a stack frame that stores parameters and the return address to manage multiple active calls.

Practice

1. What is the main purpose of an activation record in a program's execution?

easy

A. To store information about a function call such as parameters and local variables

B. To manage the computer's memory allocation for the entire program

C. To compile the source code into machine code

D. To display output on the screen

Solution

1. Step 1: Understand what an activation record stores

   An activation record holds details about a specific function call, including parameters, local variables, and return address.

2. Step 2: Identify the main purpose

   This helps the program keep track of function calls and return correctly after execution.

3. Final Answer:

   To store information about a function call such as parameters and local variables -> Option A

4. Quick Check:

   Activation record = function call info [OK]

Hint: Activation record = function call details stored [OK]

Common Mistakes:

• Confusing activation record with overall memory management
• Thinking activation record compiles code
• Assuming activation record handles output display

2. Which of the following correctly describes the call stack's behavior during function calls?

easy

A. It executes functions in parallel without stacking

B. It removes the activation record before the function starts

C. It stores all activation records in a queue structure

D. It adds a new activation record on top when a function is called

Solution

1. Step 1: Recall how the call stack works

   The call stack adds (pushes) a new activation record on top each time a function is called.

2. Step 2: Confirm the correct description

   This stacking ensures the program knows which function is currently running and where to return after completion.

3. Final Answer:

   It adds a new activation record on top when a function is called -> Option D

4. Quick Check:

   Call stack pushes activation records [OK]

Hint: Call stack pushes new records on function call [OK]

Common Mistakes:

• Thinking activation records are removed before function starts
• Confusing stack with queue behavior
• Assuming functions run in parallel without stacking

3. Consider this sequence of function calls: main() calls funcA(), which calls funcB(). What is the order of activation records on the call stack just before funcB() finishes?

medium

A. funcB at bottom, funcA in middle, main on top

B. funcA at bottom, main in middle, funcB on top

C. main at bottom, funcA in middle, funcB on top

D. funcB at bottom, main in middle, funcA on top

Solution

1. Step 1: Understand call stack order

   The call stack adds activation records in order of calls: main first, then funcA, then funcB on top.

2. Step 2: Determine stack order before funcB finishes

   Since funcB is currently running, its record is on top, with funcA below it, and main at the bottom.

3. Final Answer:

   main at bottom, funcA in middle, funcB on top -> Option C

4. Quick Check:

   Call stack order = main, funcA, funcB [OK]

Hint: Last called function's record is on top [OK]

Common Mistakes:

• Reversing the order of activation records
• Confusing bottom and top of the stack
• Assuming parallel execution changes stack order

4. A programmer notices that after a function returns, the call stack still contains its activation record. What is the most likely cause?

medium

A. The function was never called

B. The activation record was not properly removed (popped) from the stack

C. The call stack is implemented as a queue

D. The program has no functions

Solution

1. Step 1: Understand normal call stack behavior on return

   When a function finishes, its activation record should be removed (popped) from the call stack.

2. Step 2: Identify cause of leftover activation record

   If the record remains, it means the stack pop operation did not happen correctly.

3. Final Answer:

   The activation record was not properly removed (popped) from the stack -> Option B

4. Quick Check:

   Activation record must be popped after return [OK]

Hint: Function return must pop activation record [OK]

Common Mistakes:

• Assuming function was never called
• Confusing stack with queue behavior
• Ignoring that program has functions

5. In a recursive function that calls itself 4 times before returning, how many activation records will be on the call stack at the deepest point of recursion?

hard

A. 5

B. 2

C. 1

D. 4

Solution

1. Step 1: Understand recursion and activation records

   Each recursive call adds a new activation record to the call stack.

2. Step 2: Count total activation records

   If the function calls itself 4 times, there are 4 new calls plus the original call, totaling 5 activation records on the stack.

3. Final Answer:

   5 -> Option A

4. Quick Check:

   Recursive calls + original = 5 activation records [OK]

Hint: Count original call plus recursive calls [OK]

Common Mistakes:

• Counting only recursive calls, ignoring original
• Assuming recursion does not add activation records
• Confusing number of calls with return points