BCS2122DCS2192 Data Structure and Algorithm

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BCS2122/DCS2192Data Structure and Algorithm

• Module 4 Dynamic Allocation
• Muhammed Ramiza Ramli

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Introduction

• All of the program up to this point have used
  static variables as we are concerned.
• Fixed number and size.
• It is possible, using this techniques, to create
  as many variables as needed, use them, and
  deallocate their space so that it can be used by
  other dynamic variables.

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Example

• Refer to dynalist.c file source.

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Observation

• We defining a structure car with a few
  fields.
• We do not define any variables of this type, only
  pointers.
• We work with these three pointer which point to
  the defined structure.
• In order to do anything we need some variables,
  so we will create some dynamically

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The malloc function

• car1 (CAR )malloc(sizeof(CAR))
• malloc simply ask the system for a block of
  memory of the size specified, and gets the block
  with the pointer pointing to the first element of
  the block.

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Casting

• The malloc function returns a block with the
  pointer pointing to it being a pointer of type
  char by default.
• We can define the pointer type with a construct
  to match our pointer.
• Even if we omit the cast, most compiler will
  return a pointer correctly, give a warning.

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free

• Any dynamically memory block allocated by malloc
  can be deallocated by using free function.