Understanding Operating System CH 2

True

A large job can have problems with a first-fit memory allocation scheme.

False

A single-user system supports multiprogramming.

null entry

A(n) ____ in the busy list occurs when a memory block between two other busy memory blocks is returned to the free list.

True

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

overhead

By compacting and relocating, the Memory Manager optimizes the use of memory and thus improves throughput. However, it also requires more ____ than the other memory allocation schemes discussed in this chapter.

False

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

static

Fixed partitions are also called ____ partitions.

False

For a fixed partition system, memory deallocation is relatively complex.

True

In a dynamic partition system, a null entry in the busy list occurs when a memory block between two other busy memory blocks is returned to the free list.

True

In a fixed partition scheme, large jobs will need to wait if the large partitions are already booked, and they will be rejected if they're too big to fit into the largest partition.

relocation register

In a relocatable dynamic partition scheme, the ____ contains a value that must be added to each address referenced in a program so that the system will be able to access the correct memory addresses after relocation.

bounds register

In a relocatable dynamic partition scheme, the ____ ensures that, during execution, a program won't try to access memory locations that don't belong to it.

sequentially

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

partition size, memory address, access, and status

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

True

In the relocatable dynamic partitions scheme, the Memory Manager relocates programs to gather together all of the empty blocks and compact them to make one block of memory large enough to accommodate some or all of the jobs waiting to get in.

random access memory

Main memory is also known as ____.

defragmentation

Memory compaction is also referred to as ____.

True

Memory defragmentation is performed by the operating system to reclaim fragmented space.

percentage

One approach to performing compaction is to do it when a certain ____ of memory becomes busy.

True

One of the problems with the best-fit algorithm is that the entire table must be searched before the allocation can be made because the memory blocks are physically stored in sequence according to their location in memory.

True

Research continues to focus on finding the optimum allocation scheme.

False

Single-user contiguous allocation schemes have the problem of partition intrusion.

True

Single-user systems in a non-networked environment allocate, to each user, access to all available main memory for each job, and jobs are processed sequentially, one after the other.

relocatable dynamic partitions

Single-user, fixed partition, and dynamic partition memory schemes share unacceptable fragmentation characteristics that were resolved with the development of ____.

first-fit memory allocation

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

True

The algorithm used to store jobs into memory in a fixed partition system requires a few more steps than the one used for a single-user system because the size of the job must be matched with the size of the partition to make sure it fits completely.

False

The best-fit allocation method keeps the free/busy lists organized by memory locations, low-order memory to high-order memory.

True

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

True

The first attempt to allow for multiprogramming used fixed partitions.

False

The first-fit algorithm assumes that the Memory Manager keeps only one list containing free memory blocks.

False

The fixed partition scheme does not require that the entire program be stored contiguously and in memory from the beginning to the end of its execution.

True

The fixed partition scheme works well if all of the jobs run on the system are of the same size or if the sizes are known ahead of time and don't vary between reconfigurations.

all jobs are of similar size

The fixed partition scheme works well when ____.

loaded into memory

The four memory management techniques presented in this chapter share the requirement that the entire program being executed must be ____.

best-fit

The goal of the ____ memory allocation algorithm is to find the smallest memory block into which a job will fit.

internal fragmentation

The phenomenon of less-than-complete use of memory space in a fixed partition is called ____.

deallocation

The release of memory space by the Memory Manager is called ____.

function

When reading an instruction, the operating system can tell the ____ of each group of digits by its location in the line and the operation code.

External fragmentation

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

Compaction

____ of memory is performed by the operating system to reclaim fragmented sections of the memory space.

the process of freeing an allocated resource, whether memory space, a device, a file, or a CPU.

deallocation

a situation in which the dynamic allocation of memory creates unusable fragments of free memory between blocks of busy, or allocated, memory.

external fragmentation

a situation in which a partition is only partially used by the program; the remaining space within the partition is unavailable to any other job and therefor wasted.

internal fragmentation

(1) the process of moving a program from one area of memory to another; or (2) the process of adjusting address references in a program, by either software or hardware means, to allow the program to execute correctly when loaded in different sections of memory.

relocation