4.1. Choice of Programming Language

By relieving the brain of all unnecessary work, a good notation sets it free to concentrate on more advanced problems, and in effect increases the mental power of the race. Before the introduction of the Arabic notation, multiplication was difficult, and the division even of integers called into play the highest mathematical faculties. Probably nothing in the modern world would have more astonished a Greek mathematician than to learn that … a huge proportion of the population of Western Europe could perform the operation of division for the largest numbers. This fact would have seemed to him a sheer impossibility…. Our modern power of easy reckoning with decimal fractions is the almost miraculous result of the gradual discovery of a perfect notation.

Alfred North Whitehead

The programming language in which the system will be implemented should be of great interest to you since you will be immersed in it from the beginning of construction to the end.

Studies have shown that the programming-language choice affects productivity and code quality in several ways.

Programmers are more productive using a familiar language than an unfamiliar one. Data from the Cocomo II estimation model shows that programmers working in a language they've used for three years or more are about 30 percent more productive than programmers with equivalent experience who are new to a language (Boehm et al. 2000). An earlier study at IBM found that programmers who had extensive experience with a programming language were more than three times as productive as those with minimal experience (Walston and Felix 1977). (Cocomo II is more careful to isolate effects of individual factors, which accounts for the different results of the two studies.)

Programmers working with high-level languages achieve better productivity and quality than those working with lower-level languages. Languages such as C++, Java, Smalltalk, and Visual Basic have been credited with improving productivity, reliability, simplicity, and comprehensibility by factors of 5 to 15 over low-level languages such as assembly and C (Brooks 1987, Jones 1998, Boehm 2000). You save time when you don't need to have an awards ceremony every time a C statement does what it's supposed to. Moreover, higher-level languages are more expressive than lower-level languages. Each line of code says more. Table 4-1 shows typical ratios of source statements in several high-level languages to the equivalent code in C. A higher ratio means that each line of code in the language listed accomplishes more than does each line of code in C.

Table 4-1. Ratio of High-Level-Language Statements to Equivalent C Code

Language	Level Relative to C
C	1
C++	2.5
Fortran 95	2
Java	2.5
Perl	6
Python	6
Smalltalk	6
Microsoft Visual Basic	4.5
Source: Adapted from Estimating Software Costs (Jones 1998), Software Cost Estimation with Cocomo II (Boehm 2000), and "An Empirical Comparison of Seven Programming Languages" (Prechelt 2000).

Some languages are better at expressing programming concepts than others. You can draw a parallel between natural languages such as English and programming languages such as Java and C++. In the case of natural languages, the linguists Sapir and Whorf hypothesize a relationship between the expressive power of a language and the ability to think certain thoughts. The Sapir-Whorf hypothesis says that your ability to think a thought depends on knowing words capable of expressing the thought. If you don't know the words, you can't express the thought and you might not even be able to formulate it (Whorf 1956).

Programmers may be similarly influenced by their languages. The words available in a programming language for expressing your programming thoughts certainly determine how you express your thoughts and might even determine what thoughts you can express.

Evidence of the effect of programming languages on programmers' thinking is common. A typical story goes like this: "We were writing a new system in C++, but most of our programmers didn't have much experience in C++. They came from Fortran backgrounds. They wrote code that compiled in C++, but they were really writing disguised Fortran. They stretched C++ to emulate Fortran's bad features (such as gotos and global data) and ignored C++'s rich set of object-oriented capabilities." This phenomenon has been reported throughout the industry for many years (Hanson 1984, Yourdon 1986a).

Language Descriptions

The development histories of some languages are interesting, as are their general capabilities. Here are descriptions of the most common languages in use today.

Ada

Ada is a general-purpose, high-level programming language based on Pascal. It was developed under the aegis of the Department of Defense and is especially well suited to real-time and embedded systems. Ada emphasizes data abstraction and information hiding and forces you to differentiate between the public and private parts of each class and package. "Ada" was chosen as the name of the language in honor of Ada Lovelace, a mathematician who is considered to have been the world's first programmer. Today, Ada is used primarily in military, space, and avionics systems.

Assembly Language

Assembly language, or "assembler," is a kind of low-level language in which each statement corresponds to a single machine instruction. Because the statements use specific machine instructions, an assembly language is specific to a particular processor for example, specific Intel or Motorola CPUs. Assembler is regarded as the second-generation language. Most programmers avoid it unless they're pushing the limits in execution speed or code size.

C

C is a general-purpose, mid-level language that was originally associated with the UNIX operating system. C has some high-level language features, such as structured data, structured control flow, machine independence, and a rich set of operators. It has also been called a "portable assembly language" because it makes extensive use of pointers and addresses, has some low-level constructs such as bit manipulation, and is weakly typed.

C was developed in the 1970s at Bell Labs. It was originally designed for and used on the DEC PDP-11 whose operating system, C compiler, and UNIX application programs were all written in C. In 1988, an ANSI standard was issued to codify C, which was revised in 1999. C was the de facto standard for microcomputer and workstation programming in the 1980s and 1990s.

C++

C++, an object-oriented language founded on C, was developed at Bell Laboratories in the 1980s. In addition to being compatible with C, C++ provides classes, polymorphism, exception handling, templates, and it provides more robust type checking than C does. It also provides an extensive and powerful standard library.

C#

C# is a general-purpose, object-oriented language and programming environment developed by Microsoft with syntax similar to C, C++, and Java, and it provides extensive tools that aid development on Microsoft platforms.

Cobol

Cobol is an English-like programming language that was originally developed in 1959 1961 for use by the Department of Defense. Cobol is used primarily for business applications and is still one of the most widely used languages today, second only to Visual Basic in popularity (Feiman and Driver 2002). Cobol has been updated over the years to include mathematical functions and object-oriented capabilities. The acronym "Cobol" stands for COmmon Business-Oriented Language.

Fortran

Fortran was the first high-level computer language, introducing the ideas of variables and high-level loops. "Fortran" stands for FORmula TRANslation. Fortran was originally developed in the 1950s and has seen several significant revisions, including Fortran 77 in 1977, which added block-structured if-then-else statements and character-string manipulations. Fortran 90 added user-defined data types, pointers, classes, and a rich set of operations on arrays. Fortran is used mainly in scientific and engineering applications.

Java

Java is an object-oriented language with syntax similar to C and C++ that was developed by Sun Microsystems, Inc. Java was designed to run on any platform by converting Java source code to byte code, which is then run in each platform within an environment known as a virtual machine. Java is in widespread use for programming Web applications.

JavaScript

JavaScript is an interpreted scripting language that is loosely related to Java. It is used primarily for client-side programming such as adding simple functions and online applications to Web pages.

Perl

Perl is a string-handling language that is based on C and several UNIX utilities. Perl is often used for system administration tasks, such as creating build scripts, as well as for report generation and processing. It's also used to create Web applications such as Slashdot. The acronym "Perl" stands for Practical Extraction and Report Language.

PHP

PHP is an open-source scripting language with a simple syntax similar to Perl, Bourne Shell, JavaScript, and C. PHP runs on all major operating systems to execute server-side interactive functions. It can be embedded in Web pages to access and present database information. The acronym "PHP" originally stood for Personal Home Page but now stands for PHP: Hypertext Processor.

Python

Python is an interpreted, interactive, object-oriented language that runs in numerous environments. It is used most commonly for writing scripts and small Web applications and also contains some support for creating larger programs.

SQL

SQL is the de facto standard language for querying, updating, and managing relational databases. "SQL" stands for Structured Query Language. Unlike other languages listed in this section, SQL is a "declarative language," meaning that it does not define a sequence of operations, but rather the result of some operations.

Visual Basic

The original version of Basic was a high-level language developed at Dartmouth College in the 1960s. The acronym BASIC stands for Beginner's All-purpose Symbolic Instruction Code. Visual Basic is a high-level, object-oriented, visual programming version of Basic developed by Microsoft that was originally designed for creating Microsoft Windows applications. It has since been extended to support customization of desktop applications such as Microsoft Office, creation of Web programs, and other applications. Experts report that by the early 2000s more professional developers were working in Visual Basic than in any other language (Feiman and Driver 2002).