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24.01.2021 08:46

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Programs and programming languages
Computers can deal with different kinds of problems if they are given the right instructions for what to do. Instructions are first written in one of the high-level languages, е.g. FORTRAN, COBOL, ALGOL, PL/I, PASCAL, BASIC, or С, depending on the type of problem to be solved. А program written in one of these languages is often called а source program, and it cannot be directly processed by the computer until it has been compiled, which means interpreted into machine code. Usually а single instruction written in а high-level language, when transformed into machine code, results in several instructions. Неге is а brief description of some of the many high-level languages:

FORTRAN acronym for FORmula TRANslation. This language is used for solving scientific and mathematical problems. It consists of algebraic formulae and English phrases. It was first introduced in the United States in 1954.

COBOL acronym for COmmon Business-Oriented Language. This language is used for commercial purposes. COBOL, which is written using English statements, deals with problems that do not involve а lot of mathematical calculations. It was first introduced in 1959.

ALGOL acronym for ALGOrithmic Language. Originally called IAL, which means International Algebraic Language. It is used for mathematical and scientific purposes. ALGOL was first introduced in Europe in 1960.

PL/I Programming Language I. Developed in 1964 to combine features of COBOL and ALGOL. Consequently, it is used for data processing as well as scientific applications.

BASIC acronym for Beginner’s All-purpose Symbolic Instruction Code. Developed in 1965 at Dartmouth College in the United States for use by students who require а simple language to begin programming.

С developed in the 1970s to support the UNIX operating system. С is а highly portable general-purpose language.

Other such languages are АРL (developed in 1962), PASCAL (named after Blaise Pascal and developed in 1971), and LISP and PROLOG, both of which are used for work in artificial intelligence. LOGO is а development of LISP which has been used to develop computer-based training (СВТ) packages.

When а program written in one of these high-level languages is designed to do а specific type of work such as calculate а company's payroll or calculate the stress factor on а roof, it is called an applications program. Institutions either purchase these programs as packages or commission their own programmers to write them to meet the specifications of the users.

The program produced after the source program has been converted into machine code is referred to as an object program or object module. This is done by а computer program called the compiler, which is unique for each computer. Consequently, а computer needs its own compiler for the various high-level languages if it is expected to accept programs written in those languages. For example, in order that an IВМ RS/6000 may process а program in FORTRAN, it needs to have а compiler that would understand that particular model and the FORTRAN language as well.

The compiler is а systems program which may be written in any language, but the computer's operating system is а true systems program which controls the central processing unit (CPU), the input, the output, and the secondary memory devices. Another systems program is the linkage editor, which fetches required systems routines and links them to the object module (the source program in machine code). The resulting program is then called the load module, which is the program directly executable by the computer. Although systems programs are part of the software, they are usually provided by the manufacturer of the machine.

Unlike systems programs. software packages are sold by various vendors and not necessarily by the computer manufacturer. They are а set of programs designed to perform certain applications which conform to the particular specifications of the user. Payroll [list of employees and the amount of money to be paid to each of them] is an example of such а package which allows the user to input data — hours worked, pay rates, special deductions, names of employees — and get salary calculations as output. These packages are coded in machine language (0s and 1s) on magnetic tapes or disks which can be purchased, leased, or rented by users who choose the package that most closely corresponds to their needs.

Exercise 3. These are answers to questions about the text. Write the questions.
1)No, it is quite wordy so it is used for commercial purposes.

2)To support the UNIX operating system.

3)An applications program.

4)It is done by the compiler.

5)It fetches required systems routines and links them to the object module.

6)No, they are also sold by other vendors.