CONTIGUOUS MEMORY ALLOCATION

CONTIGUOUS MEMORY ALLOCATION

This means that each program is loaded or placed in memory locations with consecutive addresses. Such memory partitions may be defined statically or dynamically. 

The contiguous memory allocation is divided into 3 types:-

1. Fixed partition memory allocation OR Static partition memory allocation
2. Variable partition memory allocation OR Dynamic partition memory allocation
3. Relocation memory allocation

1.  Fixed partition memory allocation 

OR

 Static partition memory allocation

• In fixed partition memory allocation or static partition memory allocation, the main memory is divided into a partition. Each partition accommodates a separate job.

OR 

• This plan divides the memory into several separate fixed areas, each of which can hold one process.

The partition may be:-

• Equal sized
• Unequal sized

• The size of each partition once fixed cannot be changed during the program execution.
• Thus, the number of programs that is the degree of multiprogramming residing in memory will be bound by the number of partitions.

ADVANTAGE OF FIXED PARTITION MEMORY ALLOCATION OR STATIC PARTITION MEMORY ALLOCATION

• Suitable for the batch operating system.
• Simple and easy to implement.

DISADVANTAGE OF FIXED PARTITION MEMORY ALLOCATION OR STATIC PARTITION MEMORY ALLOCATION

• Inefficient use of memory space.
• Internet fragmentation.
• Unfitness.

2.  Variable partition memory allocation 

OR 

Dynamic partition memory allocation

• This technique is more able/efficient than the fixed portion technique.
• In Variable partition memory allocation OR Dynamic partition memory allocation technique partition are created at the time of job loading.
• Portions are created dynamically to meet the requirement of each requesting process/job.
• In this technique neither the size nor the number of partition is limited.

ADVANTAGE OF VARIABLE PARTITION MEMORY ALLOCATION OR DYNAMIC PARTITION MEMORY ALLOCATION

• Inefficient use of memory

This memory management technique starts well but after some time a large number of non-continuous holes are created in memory resulting in wastage of memory space.

In fig (i) Job 1, Job 2, Job 3, Job 4 are live in memory. Suppose Job 1 is completed and Job 5 is requesting 114 K is loaded in this partitions.

This leaves a blank space called 'hole' of size 98 K.

• Complex

This technique requires complex memory management algorithms and bookkeeping operations.

• External fragmentation

3.  Relocation memory allocation

• This management technique solves the problem of wasted free space, which is generated in the form of non-continuous holes in dynamic partition memory allocation or variable partition memory allocation.
• This method deals with the problem of external fragmentation. In this technique, the programs in the memory are reallocated in a such a way that all the holes or free spaces are moved to one end of the memory space.