processing is still an active area of artificial intelligence research. Natural languages, as they are used
by most humans, are inherently ambiguous. To understand properly all but a very limited subset of a
natural language, a human (or artificially intelligent computer system) requires a vast amount of background
knowledge that is beyond the capabilities of today’s software. Fortunately, programming languages provide
a relatively simple structure with very strict rules for forming statements that can express a solution to any
problem that can be solved by a computer.
Consider the following program fragment written in the C++ programming language:
subtotal = 25;
tax = 3;
total = subtotal + tax;
These three lines do not make up a complete C++ program; they are merely a piece of a program. The
statements in this program fragment look similar to expressions in algebra. We see no sequence of bi-
nary digits. Three words, subtotal, tax, and total, called variables, are used to hold information.
Mathematicians have used variables for hundreds of years before the first digital computer was built. In
programming, a variable represents a value stored in the computer’s memory. Familiar operators (= and +)
are used instead of some cryptic binary digit sequence that instructs the processor to perform the operation.
Since this program is expressed in the C++ language, not machine language, it cannot be executed directly
on any processor. A C++ compiler is used to translate the C++ code into machine code.
The higher-level language code is called source code. The compiled machine language code is called
the target code. The compiler translates the source code into the target machine language.
The beauty of higher-level languages is this: the same C++ source code can be compiled to different
target platforms. The target platform must have a C++ compiler available. Minor changes in the source code
may be required because of architectural differences in the platforms, but the work to move the program
from one platform to another is far less than would be necessary if the program for the new platform had
to be rewritten by hand in the new machine language. Just as importantly, when writing the program the
human programmer is free to think about writing the solution to the problem in C++, not in a specific
machine language.
Programmers have a variety of tools available to enhance the software development process. Some
common tools include:
• Editors. An editor allows the user to enter the program source code and save it to files. Most pro-
gramming editors increase programmer productivity by using colors to highlight language features.
The syntax of a language refers to the way pieces of the language are arranged to make well-formed
sentences. To illustrate, the sentence
The tall boy runs quickly to the door.
uses proper English syntax. By comparison, the sentence
Boy the tall runs door to quickly the.
is not correct syntactically. It uses the same words as the original sentence, but their arrangement
does not follow the rules of English.
Similarly, programmers must follow strict syntax rules to create well-formed computer programs.
Only well-formed programs are acceptable and can be compiled and executed. Some syntax-aware
editors can use colors or other special annotations to alert programmers of syntax errors before the
program is compiled.
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by most humans, are inherently ambiguous. To understand properly all but a very limited subset of a
natural language, a human (or artificially intelligent computer system) requires a vast amount of background
knowledge that is beyond the capabilities of today’s software. Fortunately, programming languages provide
a relatively simple structure with very strict rules for forming statements that can express a solution to any
problem that can be solved by a computer.
Consider the following program fragment written in the C++ programming language:
subtotal = 25;
tax = 3;
total = subtotal + tax;
These three lines do not make up a complete C++ program; they are merely a piece of a program. The
statements in this program fragment look similar to expressions in algebra. We see no sequence of bi-
nary digits. Three words, subtotal, tax, and total, called variables, are used to hold information.
Mathematicians have used variables for hundreds of years before the first digital computer was built. In
programming, a variable represents a value stored in the computer’s memory. Familiar operators (= and +)
are used instead of some cryptic binary digit sequence that instructs the processor to perform the operation.
Since this program is expressed in the C++ language, not machine language, it cannot be executed directly
on any processor. A C++ compiler is used to translate the C++ code into machine code.
The higher-level language code is called source code. The compiled machine language code is called
the target code. The compiler translates the source code into the target machine language.
The beauty of higher-level languages is this: the same C++ source code can be compiled to different
target platforms. The target platform must have a C++ compiler available. Minor changes in the source code
may be required because of architectural differences in the platforms, but the work to move the program
from one platform to another is far less than would be necessary if the program for the new platform had
to be rewritten by hand in the new machine language. Just as importantly, when writing the program the
human programmer is free to think about writing the solution to the problem in C++, not in a specific
machine language.
Programmers have a variety of tools available to enhance the software development process. Some
common tools include:
• Editors. An editor allows the user to enter the program source code and save it to files. Most pro-
gramming editors increase programmer productivity by using colors to highlight language features.
The syntax of a language refers to the way pieces of the language are arranged to make well-formed
sentences. To illustrate, the sentence
The tall boy runs quickly to the door.
uses proper English syntax. By comparison, the sentence
Boy the tall runs door to quickly the.
is not correct syntactically. It uses the same words as the original sentence, but their arrangement
does not follow the rules of English.
Similarly, programmers must follow strict syntax rules to create well-formed computer programs.
Only well-formed programs are acceptable and can be compiled and executed. Some syntax-aware
editors can use colors or other special annotations to alert programmers of syntax errors before the
program is compiled.
Source: freecomputerbooks.com
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