Question 1

In a single-user system, jobs are processed ____.

Accepted Answer

In a single-user system, there is only one user and the system processes the jobs one after the other in a sequential manner. It means that the next job would not start until the previous job has finished executing. Therefore, option A is the correct choice.

Question 2

The following algorithm can be described as ____. 1 Initialize memory_block(0) = 99999
2 Compute initial_memory_waste = memory_block(0) - job_size
3 Initialize subscript = 0
4 Set counter to 1
5 Do while counter <= number of blocks in memory
If job_size > memory_size(counter)
Then counter = counter + 1
Else
Memory_waste = memory_size(counter) - job_size
If initial_memory_waste > memory_waste
Then subscript = counter
Initial_memory_waste = memory_waste
Counter = counter + 1
End do
6 If subscript = 0
Then put job in waiting queue
Else
Load job into memory_size(subscript)
Adjust free/busy memory lists
7 Go fetch next job

Accepted Answer

The algorithm described is best-fit memory allocation, as it searches for the block with the smallest size that can accommodate the job, minimizing memory waste.

Question 3

In the algorithm to load a job in a single-user system, the program counter is initially set to ____.

Accepted Answer

The program counter is a register that holds the address of the next instruction to be executed. Therefore, in order to start executing a job, the program counter must be set to the address of the first memory location where the job is loaded. Hence, the initial value of the program counter is the address of the first memory location.

Question 4

The fixed partition scheme works well ____.

Accepted Answer

The fixed partition scheme works well when jobs have the same size. This is because in the fixed partition scheme, the memory is divided into fixed-size partitions, and when a job is allocated, it is assigned to a particular partition that can accommodate its size. If the jobs have different sizes, it may lead to fragmentation, which can result in inefficient use of memory. Therefore, the fixed partition scheme is best suited for situations where jobs have identical sizes.

Question 5

During compaction, the operating system must distinguish between addresses and data values, and the distinctions are not obvious once the program has been loaded into memory.

Accepted Answer

During compaction, the addresses and data values are merged and hence the operating system must distinguish between the two, which might not be obvious once the program has been loaded into memory.

Question 6

Compaction should always be performed only when there are jobs waiting to get in.

Accepted Answer

Compaction should not be performed constantly, but instead should be triggered when the storage capacity is reaching its limit or when there are fragmentation issues. Compaction takes time and resources, so it shouldn't be performed unnecessarily.

Question 7

Consider the following space requirements for jobs 1-4 and memory blocks. Assuming a best-fit scheme is used, the job,____, is placed in the last block. Jobs:
J1 10K
J2 20K
J3 30K
J4 10K
Blocks:
B1 30K
B2 15K
B3 50K
B4 20K

Accepted Answer

The best fit scheme places a job into the smallest block that it can fit into. J2 is the largest job, and B2 is the smallest block that can accommodate it, so J2 must be placed in B2. Then, the next largest job is J3, which can fit into B3, leaving only J1 and J4 to be placed in the remaining blocks. Since J1 is smaller than J4, it makes sense to place J1 in the smaller available block, B1, and then place J4 in the remaining block, B4.

Question 8

In the partition scheme, the table that the Memory Manager uses to keep track of jobs is composed of the ____.

Accepted Answer

The Memory Manager's table in a partition scheme keeps track of the partition size, memory address, access, and status of each job. These details help the Memory Manager to efficiently allocate and manage system resources. Therefore, option D is the correct answer.

Question 9

Assume the Memory Manager receives a request for a block of 200. When the best-fit algorithm is used, ____ is the beginning address of the block granted by the Memory Manager. Beginning Address Memory Block Size
4075 105
5225 5
6785 600
7560 20
7600 205
10250 4050
15125 230
24500 1000

Accepted Answer

The best-fit algorithm chooses the smallest block that is large enough to fit the requested size. 
When looking at the options, the block at beginning address 7600 is the smallest block that can accommodate 200 units. Therefore, the Memory Manager would grant the block starting at memory address 7600.

Question 10

The bounds register is used to store the highest (or lowest, depending on the specific system) location in memory accessible by each program.

Accepted Answer

The bounds register is used to store the highest memory location accessible by each program.

Question 11

Memory is allocated during garbage collection.

Accepted Answer

Garbage collection is the process of automatically freeing memory that is no longer in use, not allocating it. Memory allocation occurs when a program requests memory for new objects or data.

Question 12

The following algorithm can be described as ____. 1 Set counter to 1
2 Do while counter <= number of blocks in memory
If job_size > memory_size(counter)
Then counter = counter + 1
Else
Load job into memory_size(counter)
Adjust free/busy memory lists
Go to step 4
End do
3 Put job in waiting queue
4 Go fetch next job

Accepted Answer

This algorithm is describing the first-fit memory allocation method, where the first available block of memory that is large enough to hold a job is allocated.

Question 13

Fixed partitions are also called ____ partitions.

Accepted Answer

Fixed partitions are also known as static partitions, as the size of each partition is predetermined and does not change during runtime. The other options, complete, direct, and sized, are not commonly used terms to refer to fixed partitions.

Question 14

Consider the following space requirements for jobs 1-4 and memory blocks. Assuming a first-fit scheme is used, the job,____, is not able to run. Jobs:
J1 10K
J2 20K
J3 30K
J4 10K
Blocks:
B1 30K
B2 15K
B3 50K
B4 20K

Accepted Answer

J3 requires 30K of memory, but the largest block available is only 50K, which is enough to accommodate J3. All other jobs can fit into at least one of the available memory blocks using a first-fit scheme.

Question 15

____ consists of fragments of free memory between blocks of allocated memory.

Accepted Answer

External fragmentation occurs when there are small blocks of unused memory spaces between chunks of allocated memory, making it difficult to utilize these spaces efficiently for new allocations.

Question 16

____ has the least wasted space and the smallest partition fitting the requirements.

Accepted Answer

Best-fit memory allocation is the technique that searches for the smallest partition that meets the process's requirements. This technique typically results in the least wasted space compared to the other memory allocation techniques. Therefore, D is the best choice.

Question 17

After relocation and compaction, both the free list and the busy list are updated.

Accepted Answer

After relocation and compaction, the free list and busy list are updated as the memory addresses of the objects have changed. The objects that were originally in the free list may have been moved to a different location after compaction, therefore, the free list needs to be updated. Similarly, objects that were originally in the busy list may have been moved to a different location, hence the busy list also needs to be updated with their new memory addresses.

Question 18

The ____ keeps the free/busy lists organized by memory locations, low-order memory to high-order memory.

Accepted Answer

The first-fit memory allocation algorithm searches for the first available block of memory that is large enough to accommodate the requested size, starting from the beginning of the memory space. As it searches from low-order memory to high-order memory, it is required to keep the free/busy lists organized by memory locations. Therefore, option B is the correct answer.

Question 19

____ is the first step in the algorithm to load a job in a fixed partition.

Accepted Answer

The first step in the algorithm to load a job in a fixed partition is to determine the job's requested memory size. This is necessary to determine if the job can be loaded into an available partition. Only after this step can the algorithm proceed with comparing the job size to the size of the largest partition, setting a counter or placing the job in a waiting queue.

Question 20

The following,____, describes the first memory allocation scheme.

Accepted Answer

The description given in the question matches the characteristics of the first memory allocation scheme, where each program is loaded entirely into memory and is given as much contiguous space as it needs. This approach is known as a static allocation scheme. Choice A describes a swapping or paging scheme, B describes a dynamic allocation scheme, and C describes a hybrid scheme that incorporates elements of dynamic allocation and negotiation.

Quiz 2: Memory Management: Early Systems