2. Computer is an electronic device for storing and
processing data, typically in binary form, which is
programmed to do such a wide variety of things .
The physical devices that a computer is made of are
named as computer’s hardware and the programs that are
programmed by programmers are called as software .
A program stores in main memory which is called as RAM
as long as it is running. And by turning the computer off ,
the content of RAM is erased.
Secondary storage is a type of memory that can hold data
for long periods of time ,even when no power is connected
to the computer.
3. What is a Program?
A program is a set of instructions which is related to software
of a computer that a follows it to perform a task.
5. Programming helps you understand computers. The
computer is only a tool. If you learn how to write simple
programs, you will gain more knowledge about how a
computer works.
Writing a few simple programs increases your confidence
level. Many people find great personal satisfaction in
creating a set of instructions that solve a problem.
Learning programming lets you find out quickly whether
you like programming and whether you have the analytical
turn of mind programmers need. Even if you decide that
programming is not for you, understanding the process
certainly will increase your appreciation of what
programmers and computers can do.
6. A computer’s memory is divided into tiny storage locations
known as bytes which each byte includes eight smaller
parts named bits. Each byte is only enough to store a
letter of the alphabet or a small number.
Each character or number in a byte is shown by a
computer structure , including 0 and 1, like 10011100. If
the number is more longer than the capacity of a byte we
use 2 bytes (18bits) for it .
8. As I mentioned before a computer is programmed to run a
task .
There are different languages for programming a
computer , and choosing one of these languages depends
on demand like C, C++ , Java . . .
Programing is a bunch of codes which are written in a
specific programming language by a programmer .
The statements that are written by a programmer in a
high-level language are called source code or simply
code.
Structured programming requires that programmers break
program structure into small pieces of code that are easily
understood.
10. Low-Level
Low-Level ( Machine Language)
Computer understand only a language that is known as
“machine language”.
It consists of set of instructions in form of 1 and 0.
It is difficult for human to read and write machine
language.
11. High-Level language
High level computer languages give formats close to
English language and the purpose of developing .
It helps people to write a program easily .
High level languages are basically symbolic languages
that use English words and mathematical symbols rather
than mnemonic codes.
12. Compilers and Interpreters
Because the CPU understands only machine language
instructions, programs that are written in a language
depends on human language ( high-level language ) must
be translated into machine language.
Depending on the language that a program has been
written in , the programmer will use a complier or
interpreter to make the translation .
A compiler is a program that translate a high-level
language program into a separate machine language
program.
13. How a program works?
Scientists mention CPU as “computer’s brain” because they
think CPU is smart. But CPU is an electronic device that is
designed to do specific things. In particular ,the CPU is
designed to perform operations . Such as ,
- Reading a piece of data from main memory
- Adding two numbers
- Moving a piece of data from one memory location to
another
- Determining whether one value is equal to another value
The CPU performs simple operations on pieces of data. The
CPU does nothing on its own. It has to be told what to do and
that’s the purpose of a program.
14. Fetch-Decode-Execute
cycle
When a CPU executes the instructions in a program, it is
engaged in a process that is known as the fetch-decode-
execute cycle . This cycle, Which consists of three steps, is
repeated for each instruction in the program.
Fetch: a program is a long sequence of machine language
instructions. The first step of the cycle is to fetch, or read
the next instruction from memory into the CPU.
Decode: a machine language instruction is a binary
number that represents a command that tells the CPU to
perform an operation .
Execute: the last step in the cycle is to execute , or
perform, the operation.
