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Programs and programming languages




[1] if the finished program does not run as it should  
[2]   this is quite satisfactory
if a permanent, neater and more readable flowchart is needed  
[3]   the word 'start must be inserted inside the figure
if it is the end of the program  
[4]   neither the flowchart nor the program can be done correctly
[5] if documentation isn't available  
[6]   flowcharting is one of the first things a student programmer is taught

[1] Computers can deal with different kinds of problems if they are given 1
the right instructions for what to do. Instructions are first written in one
of the high-level languages, e.g. FORTRAN, COBOL, ALGOL, PL/1,
or BASIC,depending on the type of problem to be solved. A
program written in one of these languages is often called a source5

program,and it cannot be directly processed by the computer until it
has been compiled,which means interpreted into machine code.
Usually a single instruction written in a high-levellanguage, when
transformed into machine code, results in several instructions. Here is a
brief description of some of the many high-level languages: 1 o

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 15

language is used for commercial purposes. COBOL, which is written using English statements, deals with problems that do not involve a lot of mathematical calculations. It was first introduced in 1959.

ALGOL acronym for ALGOrithmic Language. Originally called 20

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

PL/1 Programming Language 1. Developed in 1964 to combine

features of COBOL and ALGOL. Consequently, it is 25 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 a simple 30 language to begin programming.


Other such languages are APL (developed in 1962), PASCAL (named

after Blaise Pascal and developed in 1971), and LISP and PROLOG,

both of which are being developed for work in artificial intelligence.

The language C (developed in the late 1970s at the Bell Telephone 35

Laboratory) is also now widely used for systems programming.

[2] When a program written in one of these high-level languages is designed to do a specific type of work such as calculate a company's payroll or calculate the stress factor on a roof, it is called an applicationsprogram. Institutions either purchase these programs as packagesor commission 40 their own programmers to write them to meet the specifications of the users.

[3] The program produced after the source program has been converted
into machine code is referred to as an object programor object module.
This is done by a computer program called the compiler,which is 45

unique for each computer. Consequently, a 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 IBM
system 370 may process a program in FORTRAN, it needs to have a
compiler that would understand that particular model and the
FORTRAN language as well. 50

[4] The compiler is a systems program,which may be written in any
language, but the computer's operating systemis a true systems
program which controls the central processing unit (CPU), the input,
the output, and the secondary memory devices. Another systems 55

program is the linkage editorwhich 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.

[5]Unlike systems programs, software packagesare sold by various

vendors and not necessarily by the computer manufacturer. They are a
set of programs designed to perform certain applications which conform
to internationally accepted rules, irrespective of the particular 65

specifications of the user. Payroll is an example of such a 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 Is) 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.

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