- Very important fact:
- Every thing stored inside a computer is stored as a binary number
- Note:
- Sometimes,
I will use decimal numbers
to depict the
data
stored inside
the computer
for convinience
(Because we (= humans) can interpret decimal numbers more easily than binary numbers)
- You must
always remember that
these decimal numbers are
actually
binary numbers inside
the computer
(I.e.: if you want to know what is stored inside the computer, you must convert the decimal number into a binary number !!!)
- Sometimes,
I will use decimal numbers
to depict the
data
stored inside
the computer
for convinience
- From CS170, you
know that a computer program consists of:
- Variables
- Variable = memory cells used to record (= store) values
- Statements
- Statements are
instructions (= commands)
to tell the
computer to
perform some
operation
- These instructions are stored in computer memory cells
- Statements are
instructions (= commands)
to tell the
computer to
perform some
operation
- Variables
- A program stored in
computer memory will
look like this:
Explanation:
- The computer (program) instructions are
stored at the start of
the computer memory (RAM)
- Some variables are
stored after the
program instructions
- Some variables are stored at the end of the computer memory
Note:
- Different kinds of
variables are
stored in
different ways in the
computer memory (RAM) for
management efficiency
reasons
- Class variables are stored after the program instructions
- Local and parameter variables are stored at the end of the memory (in a stack)
We will explain this in more details later in this course
- The computer (program) instructions are
stored at the start of
the computer memory (RAM)
- How is a
program stored
inside the computer (memory):
- A computer program stored
in computer memory consist of:
Content of the memory cells:
- Some memory cells contain
computer instructions
(and the computer instructions are encoded as a binary number)
- Some memory cells are used to
store
the values in a
variable
defined in the computer program
(and the value of the variable is encoded using the representation system of the variable's data type:
- The value is encoded in 2's complement code if the variable type is int, short or byte
- The value is encoded in IEEE 754 code if the variable type is double or float
- The value is encoded in ASCII code if the variable type is char
)
- Some memory cells are unused
- Some memory cells contain
computer instructions
- A computer program stored
in computer memory consist of:
- Very important:
- The computer system
knows:
- Which memory cells are used
- Which memory cells are unused !!!!
(So when the program creates a new variable, the computer system will use some unused memory cells to store the value of the new variable)
- The computer system
knows: