deadlock: deadlock is a situation in which two or more processes are waiting for other to finish,and thus neither ever does.In operating system deadlock may occur because of two or more processes are waiting because a resource requested is held by another process,which in turn also waiting for another resources.

four necessary conditions of deadlock:

1. mutual exclusion
2. hold and wait
3. no preemption
4. circular waiting

Fragmentation: fragmentation is a process in which storage space is used unsufficiently.

that means as process are losded and removed from memory,the free memory space is broken into little spaces . after sometimes that process cannot be allocated to memory considring their small size and memory blocks are remains unused. this problrm is known as

fragmentation.

Types of fragmentation: it is basically two types

1. internal fragmentation
2. external fragmentation

internal fragmentation: due to fixed partition memory can only be provided in chunks which are divisible by 4,8, or 16.so if we need 23 bytes of memory ,24 is automatically assigned to

that particular process.that means memory block assigned to a process is bigger.some par-

tions of memory is unused as it cannot be used by another process.this is known as internal fragmentation.

external fragmentation: in this type of fragmentation total memory space is enough to satisfy

a request or to reside a process in it ,but it is not contiguous so it cannot be used.