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COMPUTER SOFTWARE

Computer programs, known as software, are sets of instructions written by a computer programmer to control the computer’s activities.

Programming languages underwent considerable development in the 1950s. Programming gave computer professionals a way to control the computer with stored programs rather than with the “hard-wired” instructions that were previously used.

In the early days, computer programmers used punched cards and a binary coding system to program the computer. Today’s programming languages use code that is much more like the English language.

When developing software, programmers must carefully consider the computer-user interface, or the way in which information is presented to the user.

The group of programs that control and coordinate the resources and operations of the computer system are known collectively as the systems software. The system software of a host computer must manage computer resources for the many users who may be in contact with the computer simultaneously. The system software for a personal computer is usually provided as a set of specialized utility programs that are used to manage the computer and its attached input and output devices. Collectively these programs are known as the computer’s operating system.

Today’s large host computers operate in a multi-user environment: that is, the systems software must keep track of many users who are all in contact with the computer at the same time.

The control commands used with mainframe computers are often referred to as job-control languages (JCLs).

Application software is widely used to accomplish a user’s computer tasks; it is used for such things as entering and editing text (word processing and desktop publishing), for entering and manipulating numeric data (spreadsheets and other business programs), and for recordkeeping (database management). These programs are known as general-purpose applications. Because they are also used by a wide variety of users in different environments, they are also known as horizontal applications. Specialized applications programs that are designed to meet the needs of a narrowly defined group of users are called vertical applications.

Programming software is used by computer programmers to create all of the computer programs we use, including applications programs and systems software programs. A programming language has words, symbols, and rules of grammar (known as the syntax of the language).

Machine languages are designed for a specific type of computer processor and are referred to as low-level languages. They were first developed in the early days of computing and are therefore known as first-generation languages.

Assembly languages (second-generation languages) are similar to machine languages but instead of using the binary form of instructions, more English-like instructions are used.

High-level programming languages, referred to as third-generation languages, are more English-like and they are easier to use than the older machine and assembly languages. They are also more machine independent (the programs created can often be used on more than one type of computer with little modification).

Programs, not written in machine language, must be translated into a form that can be understood by the computer. They can be compiled as a whole using a compiler or acted upon instruction-by-instruction using an interpreter. High-level computer languages are also known as procedural languages; newer, fourth-generation languages (4GLs) require less specificity and are referred to as nonprocedural languages. A query language i s used to organize data and print out reports based on information stored in a database. These newer types of programs use a natural language approach and are often referred to as very high-level languages or fifth generation languages.

Object-oriented programming (OOP) languages are based on a concept of “objects” that combine stored data and programming instructions. Object-oriented authoring (OOA) systems give non-professionals a way to create their own custom applications by providing programmable objects and graphics tools that can be used to design the screen display.

An algorithm is the sequence of steps that will form a programmed solution to a problem. It can be expressed in a flowchart (an outline of the program using a set of geometric symbols) or as pseudocode (a set of statements in English that map out the program plan).

Errors in computer programs are often referred to as bugs and finding and fixing a program’s errors is referred to as debugging.

16. Ответьте на вопросы:

1. What are the identifying characteristics of the three basic types of computer software?

2. Why is the computer-user interface an important consideration in the development of software applications?

3. What is a horizontal program and how does it differ from a vertical application program?

4. What is the difference between a compiler and an interpreter?

5. Why is each succeeding generation of programming language easier to use than the previous generation?

6. What is the difference between a flowchart and pseudocode?

7. What does it mean to “debug” a computer program?

8. What is the difference between a syntax error and an error in logic?

9. What is the difference between programmer documentation and end-user documentation?