computer
Tuesday, November 16, 2010
Computer history
The first computers were people! That is, electronic computers (and the earlier mechanical computers) were given this name because they performed the work that had previously been assigned to people. "Computer" was originally a job title: it was used to describe those human beings (predominantly women) whose job it was to perform the repetitive calculations required to compute such things as navigational tables, tide charts, and planetary positions for astronomical almanacs. Imagine you had a job where hour after hour, day after day, you were to do nothing but compute multiplications. Boredom would quickly set in, leading to carelessness, leading to mistakes. And even on your best days you wouldn't be producing answers very fast. Therefore, inventors have been searching for hundreds of years for a way to mechanize (that is, find a mechanism that can perform) this task.
fundamental data types
Fundamental data types
When programming, we store the variables in our computer's memory, but the computer has to know what kind of data we want to store in them, since it is not going to occupy the same amount of memory to store a simple number than to store a single letter or a large number, and they are not going to be interpreted the same way.The memory in our computers is organized in bytes. A byte is the minimum amount of memory that we can manage in C++. A byte can store a relatively small amount of data: one single character or a small integer (generally an integer between 0 and 255). In addition, the computer can manipulate more complex data types that come from grouping several bytes, such as long numbers or non-integer numbers.
Next you have a summary of the basic fundamental data types in C++, as well as the range of values that can be represented with each one:
Name | Description | Size* | Range* |
---|---|---|---|
char | Character or small integer. | 1byte | signed: -128 to 127 unsigned: 0 to 255 |
short int ( short ) | Short Integer. | 2bytes | signed: -32768 to 32767 unsigned: 0 to 65535 |
int | Integer. | 4bytes | signed: -2147483648 to 2147483647 unsigned: 0 to 4294967295 |
long int ( long ) | Long integer. | 4bytes | signed: -2147483648 to 2147483647 unsigned: 0 to 4294967295 |
bool | Boolean value. It can take one of two values: true or false. | 1byte | true or false |
float | Floating point number. | 4bytes | +/- 3.4e +/- 38 (~7 digits) |
double | Double precision floating point number. | 8bytes | +/- 1.7e +/- 308 (~15 digits) |
long double | Long double precision floating point number. | 8bytes | +/- 1.7e +/- 308 (~15 digits) |
wchar_t | Wide character. | 2 or 4 bytes | 1 wide character |
* The values of the columns Size and Range depend on the system the program is compiled for. The values shown above are those found on most 32-bit systems. But for other systems, the general specification is that
int
has the natural size suggested by the system architecture (one "word") and the four integer types char
, short
, int
and long
must each one be at least as large as the one preceding it, with char
being always one byte in size. The same applies to the floating point types float
, double
and long double
, where each one must provide at least as much precision as the preceding one.
identifiers
Identifiers
A valid identifier is a sequence of one or more letters, digits or underscore characters (_
). Neither spaces nor punctuation marks or symbols can be part of an identifier. Only letters, digits and single underscore characters are valid. In addition, variable identifiers always have to begin with a letter. They can also begin with an underline character (_
), but in some cases these may be reserved for compiler specific keywords or external identifiers, as well as identifiers containing two successive underscore characters anywhere. In no case can they begin with a digit.Another rule that you have to consider when inventing your own identifiers is that they cannot match any keyword of the C++ language nor your compiler's specific ones, which are reserved keywords. The standard reserved keywords are:
asm, auto, bool, break, case, catch, char, class, const, const_cast, continue, default, delete, do, double, dynamic_cast, else, enum, explicit, export, extern, false, float, for, friend, goto, if, inline, int, long, mutable, namespace, new, operator, private, protected, public, register, reinterpret_cast, return, short, signed, sizeof, static, static_cast, struct, switch, template, this, throw, true, try, typedef, typeid, typename, union, unsigned, using, virtual, void, volatile, wchar_t, while
Additionally, alternative representations for some operators cannot be used as identifiers since they are reserved words under some circumstances:
and, and_eq, bitand, bitor, compl, not, not_eq, or, or_eq, xor, xor_eq
Your compiler may also include some additional specific reserved keywords.
Very important: The C++ language is a "case sensitive" language. That means that an identifier written in capital letters is not equivalent to another one with the same name but written in small letters. Thus, for example, the
RESULT
variable is not the same as the result
variable or the Result
variable. These are three different variable identifiers.
c++ progamming
These tutorials explain the C++ language from its basics up to the newest features of ANSI-C++, including basic concepts such as arrays or classes and advanced concepts such as polymorphism or templates. The tutorial is oriented in a practical way, with working example programs in all sections to start practicing each lesson right away.
intoduction:
1. Instructions for use:- This tutorial is for those people who want to learn programming in C++ and do not necessarily have any previous knowledge of other programming languages. Of course any knowledge of other programming languages or any general computer skill can be useful to better understand this tutorial, although it is not essential.
2. Basic of C++:-
c. Variables,data types:
The whole process that you have just done with your mental memory is a simile of what a computer can do with two variables. The same process can be expressed in C++ with the following instruction set:
Obviously, this is a very simple example since we have only used two small integer values, but consider that your computer can store millions of numbers like these at the same time and conduct sophisticated mathematical operations with them.
Therefore, we can define a variable as a portion of memory to store a determined value.
Each variable needs an identifier that distinguishes it from the others. For example, in the previous code the variable identifiers were
intoduction:
1. Instructions for use:- This tutorial is for those people who want to learn programming in C++ and do not necessarily have any previous knowledge of other programming languages. Of course any knowledge of other programming languages or any general computer skill can be useful to better understand this tutorial, although it is not essential.
2. Basic of C++:-
a. Structure of a program:
// my first program in C++
#include<stdio.h>
#include<conio.h>
void main{
printf("hello! everycody ....");
}
this is the basic structure of printing sentence.
eg; hello! everybody....
b.header files:
#include<stdio.h>
#include<conio.h>
#include <iostream> etc,.
c. Variables,data types:
The whole process that you have just done with your mental memory is a simile of what a computer can do with two variables. The same process can be expressed in C++ with the following instruction set:
1 2 3 4 |
|
Obviously, this is a very simple example since we have only used two small integer values, but consider that your computer can store millions of numbers like these at the same time and conduct sophisticated mathematical operations with them.
Therefore, we can define a variable as a portion of memory to store a determined value.
Each variable needs an identifier that distinguishes it from the others. For example, in the previous code the variable identifiers were
a
, b
and result
, but we could have called the variables any names we wanted to invent, as long as they were valid identifiers.web page and web page designing
Web design is a broad term used to encompass the way that content (usually hypertext or hypermedia) that are delivered to an end-user through the World Wide Web, using a Web browser or other Web-enabled software is displayed. The intent of web design is to create a website—a collection of online content including documents and applications that reside on a Web server/servers. The website may include text, images, sounds and other content, and may be interactive.
Web design involves the structure of the website including the information architecture (navigation schemes and naming conventions), the layout or the pages (wireframes or page schematics are created to show consistent placement of items including functional features), and the conceptual design with branding.
All websites should begin with a clear strategy so that it is apparent what they are trying to achieve. The strategy then enables the design to fullfill defined goals.
Web design involves the structure of the website including the information architecture (navigation schemes and naming conventions), the layout or the pages (wireframes or page schematics are created to show consistent placement of items including functional features), and the conceptual design with branding.
All websites should begin with a clear strategy so that it is apparent what they are trying to achieve. The strategy then enables the design to fullfill defined goals.
progamming languages
A programming language is an artificial language designed to express computations that can be performed by a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine, to express algorithms precisely, or as a mode of human communication.
Many programming languages have some form of written specification of their syntax (form) and semantics (meaning). Some languages are defined by a specification document. For example, the C programming language is specified by an ISO Standard. Other languages, such as Perl, have a dominant implementation that is used as a reference.
The earliest programming languages predate the invention of the computer, and were used to direct the behavior of machines such as Jacquard looms and player pianos. Thousands of different programming languages have been created, mainly in the computer field, with many more being created every year. Most programming languages describe computation in an imperative style, i.e., as a sequence of commands, although some languages, such as those that support functional programming or logic programming, use alternative forms of description.
Many programming languages have some form of written specification of their syntax (form) and semantics (meaning). Some languages are defined by a specification document. For example, the C programming language is specified by an ISO Standard. Other languages, such as Perl, have a dominant implementation that is used as a reference.
The earliest programming languages predate the invention of the computer, and were used to direct the behavior of machines such as Jacquard looms and player pianos. Thousands of different programming languages have been created, mainly in the computer field, with many more being created every year. Most programming languages describe computation in an imperative style, i.e., as a sequence of commands, although some languages, such as those that support functional programming or logic programming, use alternative forms of description.
progamming
Computer programming (often shortened to programming or coding) is the process of designing, writing, testing, debugging / troubleshooting, and maintaining the source code of computer programs. This source code is written in a programming language. The purpose of programming is to create a program that exhibits a certain desired behaviour. The process of writing source code often requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms and formal logic.
There is an ongoing debate on the extent to which the writing of programs is an art, a craft or an engineering discipline.[1] In general, good programming is considered to be the measured application of all three, with the goal of producing an efficient and evolvable software solution (the criteria for "efficient" and "evolvable" vary considerably). The discipline differs from many other technical professions in that programmers, in general, do not need to be licensed or pass any standardized (or governmentally regulated) certification tests in order to call themselves "programmers" or even "software engineers." However, representing oneself as a "Professional Software Engineer" without a license from an accredited institution is illegal in many parts of the world.However, because the discipline covers many areas, which may or may not include critical applications, it is debatable whether licensing is required for the profession as a whole. In most cases, the discipline is self-governed by the entities which require the programming, and sometimes very strict environments are defined (e.g. United States Air Force use of AdaCore and security clearance).
There is an ongoing debate on the extent to which the writing of programs is an art, a craft or an engineering discipline.[1] In general, good programming is considered to be the measured application of all three, with the goal of producing an efficient and evolvable software solution (the criteria for "efficient" and "evolvable" vary considerably). The discipline differs from many other technical professions in that programmers, in general, do not need to be licensed or pass any standardized (or governmentally regulated) certification tests in order to call themselves "programmers" or even "software engineers." However, representing oneself as a "Professional Software Engineer" without a license from an accredited institution is illegal in many parts of the world.However, because the discipline covers many areas, which may or may not include critical applications, it is debatable whether licensing is required for the profession as a whole. In most cases, the discipline is self-governed by the entities which require the programming, and sometimes very strict environments are defined (e.g. United States Air Force use of AdaCore and security clearance).
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