How
a computer stores programs in memory
§A
computer keeps data and programs in storage as follows:
§Primary
storage—Otherwise known as random access memory (RAM), it is made of memory
chips. In common usage, it refers only to a computer’s main memory, the fast
semiconductor storage (RAM) directly connected to the processor.
§Secondary
storage—Otherwise known as a hard drive, it consists of a read/write head that
floats above rotating platters coated with a magnetic material.
Memory–Stacks
and Heaps
§Variables
are stored in either a stack or heapbased on their type:
§Value
types (e.g.: int,
double,
float)
go on the stack.
§Reference
types (String,
Object)
go on the heap.
* Value types in classes are stored with the
instance of the class on the heap.
The
stack
§Values
in the stack are managed without garbage collection because items are added and
removed from the stack as last in, first out (LIFO) every time you enter or
exit a scope, like a method or statement
A
StackOverFlowException
occurs because you have used up all the available space in the stack.
Memory–Stacks
and Heaps (continued)
§The
heap
§A
heap-based memory allocation occurs when
we create a new object, at which point the compiler figures out how much memory
is needed and allocates an appropriate amount of memory space and returns a
reference representing the memory address.
§A
heap is used for dynamic allocation of memory.
§The
Microsoft .NET Framework uses garbage collection to free up space during run
time.
§Garbage
collection
is an automatic process for recovery of heap memory. Blocks of memory that had been allocated but
are no longer in use are freed, and blocks of memory still in use may be moved
to consolidate the free memory into larger blocks.
Data
Types
§Numeric
data types
§Integral
types (e.g.: byte, char, int)
§Floating-point
types (float,
double)
§Decimal
Boolean
§Example: bool done
= false;
Integral
Types
Floating-Point
Types
Decimal
Type
Using
the Numeric Data Types
byte numKids
= 15;
char letter = ‘p’;
int
worldPopulation
= 6692030277;
float money = 201.00f;
double lotsaMoney
= 2.4E+12;
decimal testGrade
= 89.5m;
Lesson
Review
§Describe
how the program statement below is stored in memory:
int
tennisPoints
= 30;
§Identify
the appropriate data types for each of the following values.
§4233423.93
§100
§-2323
§true
