Transcript Document

Chapter 1
The C++ Language
Objectives
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Describe various types of programs
Describe the role of the operating system
Describe how a computer gets instructions
Describe the role of the programming
language, high- and low-level languages,
interpreters, and compilers
Explain the structure of a C++ program
What is a computer program?
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Computers are just machines and must follow
directions.
Directions are grouped into logical sequences
to create programs.
Programs that perform specific tasks such as
word processing are called application
programs.
When a computer is first turned on, it must
follow the instructions embedded in ROM.
Operating Systems
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The operating system takes charge of
fundamental system operations
including:
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Managing hardware
Maintaining file systems
Controlling input and output
Loading and executing programs
The Computer’s Language
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The microprocessor is the device that actually
processes the instructions given to the
computer.
Each microprocessor has its own instruction
set that it can understand.
The instructions provided to the
microprocessor must be in machine language.
Machine language is a combination of circuits
that can be represented with the binary
number system.
Introduction to Programming Languages
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Programming languages can be
understood by people and computers.
Each language has its own set of rules
and vocabulary.
Some are very much like English, while
others are not.
Assembly Language
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Uses numbers and letters to represent
machine language instructions.
An assembler is needed to change the
programmer’s code into machine language.
Examples of statements might look like the
following:
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PUSH BP
MOV BP, SP
MOV SI, 0002
Low Level Languages
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It is necessary for the programmer to
know the instruction set of the
microprocessor.
Programs are specific to a
microprocessor.
Low level programs take up less
memory.
You can do anything that the hardware
will allow.
High-level Languages
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One command may represent many
microprocessor instructions.
You can write programs more quickly.
Instructions are usually more easy to
read.
Easier to move between computers.
Examples of Languages
High-level
 C++
 Java
 Basic
 Pascal
 Visual Basic
Low-level
 Machine language
 Assembly language
Interpreters
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Translate the source code of a high
level language into machine language
code known as object code.
Each instruction is interpreted as it is
needed.
The interpreter must be loaded into
memory first.
Object code is not saved.
Compilers
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Also translate high level source into
object code.
Makes the translation once and saves
an object file.
The object file is combined with other
machine language by the linker.
The linker generates the executable file.
C++ Program Structure
C++ has some major elements:
 Comments
 Compiler directives
 Main function
 Braces
 Statements
Comments
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Comments are ignored by the compiler.
They are used to explain the purpose of
the program, explain the source code,
identify the parts of the program or
store the names of the programmers.
Comments begin with a double forward
slash (//).
Compiler Directives
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Instructions to the compiler, not really
part of the C++ language.
A common directive is the #include
directive which inserts other prewritten
code into your program.
Includes are usually used to add
additional functionality such as
input/output to your program.
Main function
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A function is a block of code that carries
out a specific task.
Programs are usually divided into many
functions, but the main function always
runs first.
Functions are typically called from other
parts of the program and they might
return a value.
Braces
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Braces are used to mark the beginning
and end of a block of code.
Aligning the indention of opening and
closing braces can make it easier to
quickly identify blocks of code.
Statements
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Statements are instructions that make
the program work.
Each statement must end with a
semicolon.
Directives and function declarations do
not end with semicolons.
C++ is case sensitive so capitalization
in statements does matter.
From source code to finished product
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Type source code into text editor.
Compile the program into object code.
Link the object code with other machine
language to generate an executable file.
The executable file can be run.
Summary
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Computers follow instructions called
programs.
Application programs perform specific
tasks.
Operating systems manage
fundamental computer activities.
The microprocessor processes each
instruction.
Summary
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An interpreter or compiler must translate high
level languages into machine language.
Experience will teach you what language is
appropriate for a specific task.
Comments are ignored by the compiler.
Directives are commands for the compiler.
Summary
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All C++ programs have a main function. The
main function is where the program begins
running.
Braces mark the beginning and end of blocks
of code.
Statements are the lines of code the
computer executes.
Each statement ends with a semicolon.
C++ is case sensitive and it ignores extra
space.